Natural History Museum Library 000163823 PHILOSOPHICAL TRANSACTIONS OP THE ROYAL society OR LONDON. FOR THE YEAR MDCCCLXV. VOL. 155. LONDON: PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. MDCCCLXV. ADVERTISEMENT. The Committee appointed by the Royal Society to direct the publication of the Philosophical Transactions , take this opportunity to acquaint the Public, that it fully appears, as well from the Council-books and Journals of the Society, as from repeated declarations which have been made in several former Transactions , that the printing of them was always, from time to time, the single act of the respective Secretaries till the Forty-seventh Volume; the Society, as a Body, never interesting themselves any further in their publication, than by occasionally recommending the revival of them to some of their Secretaries, when, from the particular circumstances of their affairs, the Transactions had happened for any length of time to be intermitted. And this seems principally to have been done with a view to satisfy the Public, that their usual meetings were then continued, for the improvement of knowledge, and benefit of mankind, the great ends of their first institution by the Eoyal Charters, and which they have ever since steadily pursued. But the Society being of late years greatly enlarged, and their communications more numerous, it was thought advisable that a Committee of their members should be appointed, to reconsider the papers read before them, and select out of them such as they should judge most proper for publication in the future Transactions; which was accordingly done upon the 26th of March 1752. And the grounds of their choice are, and will continue to be, the importance and singularity of the subjects, or the advantageous manner of treating them ; without pretending to answer for the certainty of the facts, or propriety of the reasonings, contained in the several papers so published, which must still rest on the credit or judgement of their respective authors. It is likewise necessary on this occasion to remark, that it is an established rule of the Society, to which they will always adhere, never to give their opinion, as a Body, upon any subject, either of Nature or Art, that comes before them. And therefore the a 2 [ iv ] thanks, which are frequently proposed from the Chair, to be given to the authors of such papers as are read at their accustomed meetings, or to the persons through whose hands they received them, are to be considered in no other light than as a matter of civility, in return for the respect shown to the Society by those communications. The like also is to be said with regard to the several projects, inventions, and curiosities of various kinds, which are often exhibited to the Society ; the authors whereof, or those who exhibit them, frequently take the liberty to report and even to certify in the public newspapers, that they have met with the highest applause and approbation. And therefore it is hoped that no regard will hereafter be paid to such reports and public notices ; which in some instances have been too lightly credited, to the dishonour of the Society. The Meteorological Journal hitherto kept by the Assistant Secretary at the Apart- ments of the Eoyal Society, by order of the President and Council, and published in the Philosophical Transactions, has been discontinued. The Government, on the recom- mendation of the President and Council, has established at the Eoyal -Observatory at Greenwich, under the superintendence of the Astronomer Eoyal, a Magnetical and Meteorological Observatory, where observations are made on an extended scale, which are regularly published. These, which correspond with the grand scheme of observations now carrying out in different parts of the globe, supersede the necessity of a continuance of the observations made at the Apartments of the Eoyal Society, which could not be rendered so perfect as was desirable, on account of the imperfections of the locality and the multiplied duties of the observer. A List of Public Institutions and Individuals, entitled to receive a Copy of the Philosophical Transactions of each year, on making application for the same directly or through their respective agents, within five years of the date of publication. Observatories. Armagh. Cape of Good Hope. Dublin. Edinburgh. Greenwich. Kew. Liverpool. Madras. Oxford (Radcliffe). Institutions. Barbadoes Library and Museum. Calcutta Asiatic Society. Geological Museum. Cambridge Philosophical Society. Cape Town South African Library. Dublin Royal Dublin Society. Royal Irish Academy. Edinburgh Royal Society. London Admiralty Library. Chemical Society. College of Surgeons. Entomological Society. Geological Society. Geological Survey of Great Britain. Horticultural Society. Institute of British Architects. Institution of Civil Engineers. Linnean Society. London Institution. Royal Asiatic Society. Royal Astronomical Society. Royal College of Physicians. Royal Geographical Society. Royal Institution of Great Britain. Royal Medical and Chirurgical Society. Royal Society of Literature. Society of Antiquaries. Society of Arts. The Queen’s Libraiy. The Treasury Library. United Service Museum. Zoological Society. Halt a Public Library. Manchester Literary and Philosophical Society. Melbourne University Library. Montreal McGill College. Oxford Ashmolean Society. Radcliffe Library. Swansea Royal Institution. Sydney University Library. Woolwich Royal Artillery Library. Belgium. Brussels Academie Royale de Medecine. Royal Academy of Sciences. DenmarTc. Copenhagen Royal Society of Sciences. France. Montpellier Academy of Sciences. Eaculte de Medecine. Paris Academy of Sciences. Depot de la Marine. Ecole des Mines. Geographical Society. Geological Society. Jardin des Plantes. Societe d’Encouragement pour l’lndustrie Rationale. Toulouse Academy of Sciences. Germany. Altona Observatory. Berlin Royal Academy of Sciences. Society of Experimental Philosophy. Briinn Haturforschender Yerein. Dresden Caesarean Acad, of naturalists. Erankfort natural History Society. Giessen University. Gottingen University. Hamburg naturwissenschaftlicher-Yerein. Konigsberg Koniglichen Physikalisch Okonomischen Gesellschaft. Leipzig Royal Saxon Society of Sciences. Mannheim ...... Observatory. Munich Royal Academy of Sciences. Prague Bohemian Society of Sciences. Vienna Imperial Academy of Sciences. Geologische Reiehsanstalt. Wurzburg Physico-Medical Society. A List of Public Institutions and Individuals, entitled to receive a Copy of the Philosophical Transactions of each year, on making application for the same directly or through their respective agents, within five years of the date of publication ( continued ). Hungary. Pesth Hungarian Academy of Sciences. Italy. Bologna Academy of Sciences. Catanea Accademia Gioenia di Scienze Naturali. Florence Royal Observatory. Milan Institute of Sciences, Letters, and Arts. Modena Italian Society of Sciences. Naples Institute of Sciences. Palermo Academy of Sciences and Letters. Rome Academy de’ Nuovi Lincei. Collegio Romano. Turin Royal Academy of Sciences. Venice Institute of Sciences, Letters, and Arts. Java. Batavia .......... Batavian Society of Sciences. Netherlands. Amsterdam ...... Royal Institute. Haarlem ........ Dutch Society of Sciences. Rotterdam ...... Batavian Society of Experimental Philosophy. Portugal. Lisbon Royal Academy of Sciences. Russia . Kazan Imperial University. Moscow Imperial Society of Naturalists. Public Museum. Pulkowa Observatory. St. Petersburg .... Imperial Academy of Sciences. Spain. Cadiz Observatory. Madrid Royal Academy of Sciences. Sweden and Norway. . Christiania Royal University. Drontheim Royal Society of Sciences. Gottenburg Kongl. Vetenskaps oeh Vitterhets Samhalle. Stockholm Royal Academy of Sciences. Switzerland. Bern Allg. Schweizerischen Gesellschaft. Geneva Societe de Phys. et d’Hist. Naturelle. Transylvania. Klausenburg Society of the Transylvanian Museum. United States. Albany New York State Library. Boston American Academy of Sciences. Newhaven (Conn.) .The Editors of the American Journal. Cambridge Harvard University. Philadelphia Academy of Natural Sciences. American Philosophical Society. Washington ...... Smithsonian Institution. Observatory. Th Q fifty Foreign Members of the Royal Society. A List of Public Institutions and Individuals, entitled to receive a Copy of the Astro- nomical Observations (including Magnetism and Meteorology) made at the Royal Observatory at Greenwich, on making application for the same directly or through their respective agents, within two years of the date of publication. Observatories. Institutions. Altona. Aberdeen Armagh. Berlin Berlin. Bologna Breslau. Boston Brussels. Brunswick, U.S. . . Cadiz. Cambridge Cambridge. Cambridge, U.S. . . Cape of Good Hope. Dublin Coimbra. Edinburgh Copenhagen. Royal Society. Dorpat. Glasgow Dublin. Gottingen Edinburgh. Leyden Helsingfors. London Konigsberg. Royal Institution. Madras. Royal Society. Mannheim. The Queen’s Library. Marseille. Oxford Milan. Paris Munich. Board of Longitude. Oxford. Depot de la Marine. Palermo. Pesth Paris. Philadelphia Seeberg. St. Andrews Tubingen. St. Petersburg .... Turin. Stockholm Vienna. Upsal Wilna. Waterville, Maine (U.S.) . . College. Individuals. Lowndes’ Professor of Astronomy Cambridge. Plumian Professor of Astronomy Cambridge. President of the Eoyal Society London. South, Sir James . The Earl of Rosse . A List of Observatories, Institutions and Individuals, entitled to receive a Copy of the Magnetical and Meteorological Observations made at the Koyal Observatory, Greenwich. Observatories. Bombay Lieut. P. W. Mitcheson. Cambridge, United States . . Prof. J. Lovering. Christiania C. Hansteen. Gotha P. A. Hansen. Heidelberg M. Tiedemann. Kew B. Stewart. Kremsmiinster P. A. Beslhuber. Leipzig Professor Mobius. Lisbon Senhor da Silveira. Marburg Professor Gerling. Prague K. Jelinek. Stockholm Professor H. Selander. St. Petersburg (Twelve copies for distri- bution to the Bussian Mag. and Met. Obs.) Toronto Professor Kingston. Upsal Washington Professor Svanberg. Institutions. Bombay Geographical Society. Bonn University. Boston, U.S The Public Library (late Bowditch). Cambridge Philosophical Society. Cherkow University. Falmouth Boyal Cornwall Poly- technic Society. London House of Lords, Library. House of Commons, Li- brary. King’s College. Boyal Society. University College, Li- brary. Paris Meteorological Society. St. Bernard Convent. . "Washington Smithsonian Institution. Woolwich Office of Mag. and Met. Publication. Individuals. Bache, Dr. A. D Washington. Buys Ballot, Dr Utrecht. Dove, Prof. H. W Berlin. Erman, Dr. Adolph Berlin. Fox, B. W., Esq Falmouth. Harris, Sir W. Snow Plymouth. Hoskins, Dr. S. E Guernsey. Kaemtz, Prof. L. F Dorpat. Kreil, Prof. K Vienna. Lloyd, Bev. Dr Dublin. Loomis, Prof. E. Yale College, New- haven (Conn.). Phillips, Prof. John Oxford. Quetelet, A Brussels. Sabine, Major-General, B.A. . . London. Senhor da Souza Coimbra. Vernon, G. V., Esq Manchester. Wartmann, Prof. Elie Geneva. Younghusband, Col., B.A Woolwich. Adjudication of the Medals of the Royal Society for the year 1865 by the President and Council. The Copley Medal to Mons. Michel Chasles, For. Memb. R.S., for his Historical and Original researches in Pure Geometry. A Royal Medal to Joseph Prestwich, Esq., F.R.S., for his numerous and valuable Contributions to Geological Science, and more especially for his Papers published in the Philosophical Transactions, on the general question of the Excavation of River- valleys, and on the Superficial Deposits in France and England in which the Works of Man are associated with the remains of Extinct Animals. A Royal Medal to Archibald Smith, Esq., F.R.S., for his Papers in the Philosophical Transactions, and elsewhere, on the Magnetism of Ships. Professor H. E. Roscoe’s Paper, entitled “ On a Method of Meteorological Regis- tration of the Chemical Action of Total Daylight,” was appointed as the Bakerian Lecture. The Croonian Lecture was delivered by Professor Lionel Smith Beale, F.R.S. : it was entitled “ On the Ultimate Nerve-fibres distributed to Muscle and some other tissues, with Observations upon the Structure and probable Mode of Action of a Nervous Mechanism.” CONTENTS OF VOL. 155. I. On the Spectra of Ignited Gases and Vapours , with especial regard to the different Spectra of the same elementary gaseous substance. By Dr. J. Plucker, of Bonn , For. Mernb. B.S. , and Dr. J. W. Hittorf, of Munster page 1 II. On the Osteology of the genus Glyptodon. By Thomas H. Huxley, F.B.S. . . 31 III. Investigations of the Specific Heat of Solid Bodies. By Hermann Kopp. Com- municated by T. Graham, Esq., F.B.S. 71 IV. On the Composition of Sea-water in the different parts of the Ocean. By Georg Forchhammer, Professor at the University , and Director of the Polytechnic Insti- tution at Copenhagen. Communicated by the President 203 V. On the Magnetic Character of the Armour-plated Ships of the Boyal Navy, and on the Effect on the Compass of particular arrangements of Iron in a Ship. By Frederick: John Evans, Esq., Staff Commander B.N., F.B.S., Superintendent of the Compass Department of Her Majesty's Navy; and Archibald Smith, Esq., M.A., F.B.S., late Fellow of Trinity College, Cambridge, Corresponding Member of the Scientific Committee of the Imperial Bussian Navy 263 VI. On some Foraminifera from the North Atlantic and Arctic Oceans, including Davis Straits and Baffin's Bay. By W. Kitchen Parker, F.Z.S., and Professor T. Rupert Jones, F.G.S. Communicated by Professor Huxley, F.B.S. . . 325 VII. New Observations upon the Minute Anatomy of the Papillae of the Frog's Tongue. By Lionel S. Beale, M.B., F.B.S., Fellow of the Boyal College of Physicians, Professor of Physiology and of General and Morbid Anatomy in King's College, London ; Physician to King's College Hospital, &c 443 VIII. A Dynamical Theory of the Electromagnetic Field. By J. Clerk Maxwell, F.B.S 459 [ Vi ] IX. On the Embryogeny of Antedon rosaceus, Linck (Comatula rosacea of Lamarck). By Professor Wyville Thomson, LL.D., F.B.S. E., M.B.I.A., F.G.S., &c. Com- municated by Thomas Henry Huxley, F.B.S page 513 X. On the Sextactic Points of a Plane Curve. By A. Cayley, F.B.S 545 XI. A Description of some Fossil Plants , showing Structure , found in the Lower Coal- seams of Lancashire and Yorkshire. By E. W. Binney, F.B.S. . . . . 579 XII. The Bakerian Lecture. — On a Method of Meteorological Registration of the Chemical Action of Total Daylight. By Henry Enfield Roscoe, B.A., F.B.S., Professor of Chemistry in Owens College , Manchester 605 XIII. On the Commissures of the Cerebral Hemispheres of the Marsupialia and Mono- tremata as compared with those of the Placental Mammals. By William Henry Flower, F.B.S., F.B.C.S. , Conservator of the Museum of the Royal College of Surgeons of England 633 XIV. On the Sextactic Points of a Plane Curve. By William Spottiswoode, M.A., F.B.S., &c 653 XV. On the Marsupial Pouches, Mammary Glands, and Mammary Foetus of the Echidna Hystrix. By Professor Owen, F.B.S., &c 671 XVI. On the Influence of Physical and Chemical Agents upon Blood ; with special refer- ence to the mutual action of the Blood and the Respiratory Gases. By George Harley, M.D., Fellow of the Royal College of Physicians, Professor of Medical Jurisprudence in University College, London. Communicated by Professor Sharpey, M.D., Sec. B.S. 687 XVII. On a New Geometry of Space. By J. Plucker, of Bonn, For.Memb. B.S. 725 Index 793 Presents Appendix. [ i ] LIST OF ILLUSTRATIONS. Plates I. to III. — Drs. J. Plucker and J. W. Hittorf on the Spectra of Ignited Gases and Vapours. Plates IV. to IX. — Professor Huxley on the Osteology of the genus Glyptodon. Plates X. & XI. — Staff-Commander Evans and Mr. A. Smith on the Magnetic Cha- racter of the Armour-plated Ships of the Royal Navy. Plates XII. to XIX. — Mr. W. K. Parker and Professor T. R. Jones on some Forami- nifera from the North Atlantic and Arctic Oceans. Plate XX. — Professor Kopp on the Specific Heat of Solid Bodies. Plates XXI. and XXII. — Professor Beale’s New Observations upon the Minute Anatomy of the Papillae of the Frog’s Tongue. Plates XXIII. to XXVII. — Professor W. Thomson on the Embryogeny of Antedon rosaceus , Linck ( Comatula rosacea of Lamarck). Plates XXVIII. & XXIX. — Professor Roscoe on a Method of Meteorological Regis- tration of the Chemical Action of Total Daylight. Plates XXX. to XXXV. — Mr. E. W. Binney on some Lower-coal-seam Fossil Plants. Plates XXXVI. to XXXVIII. — Mr. W. H. Flower on the Cerebral Commissures of the Marsupialia and Monotremata. Plates XXXIX. to XLI. — Professor Owen on the Marsupial Pouches, Mammary Glands, and Mammary Foetus of the Echidna Eystrix. PHILOSOPHICAL TRANSACTIONS. I. On the Spectra of Ignited Gases and Vapours, with especial regard to the different Spectra of the same elementary gaseous substance. By Dr. J. Plucker, of Bonn, For. Memb. B.S., and Dr. J. W. Hittorf, of Munster. Received February 23, — Read March 3, 1864. 1. In order to obtain the spectra of all the elementary bodies, you may make use either of flame or the electric current. For this purpose flame is preferable on account of its easy management, and therefore was immediately introduced into the laboratory of the chemist. But its use is rather limited, the metals of alkalies being nearly the only sub- stances which, if introduced into flame, give spectra exhibiting well-defined bright lines. In the case of the greater number of elementary substances the temperature of flame, even if alimented by oxygen instead of air, is too low. Either these substances are not reduced into vapour by means of flame, or, if reduced, the vapour does not reach the temperature necessary to render it luminous in such a degree that by prismatic analysis we obtain its characteristic rays. The electric current, the heating-power of which may be indefinitely increased by increasing its intensity, is alone fitted to produce the pecu- liar spectra of all elementary bodies. 2. In applying the electric current we may proceed in two ways. In one mode of proceeding the substance to be examined by its spectrum is at the same time, by means of the current, transformed into vapour and rendered luminous. In the other mode the substance is either in the gaseous state, or, if not, has been converted into it by means of a lamp, and the electric current ignites the substance in passing through. 3. The first way of proceeding is the least perfect, but we are obliged to recur to it in the case of all such elementary bodies as neither by themselves nor combined with other substances can be vaporized without altering the least-fusible glass. If the sub- stance to be examined be a metal, the extremities of the conducting- wires are made of it and placed at a short distance from one another. When the strong spark of a large Leyden jar, charged by Ruhmkorff’s powerful induction-coil, is sent through the space between the two extremities of the conducting-wires, minute particles of the metal, mdccclxv. b 2 DES. J. PLUCKEE AND J. W. HITTOEF ON THE starting off from them, are volatilized: even in the gaseous state they conduct the electric current from point to point, and exhibit, while heated by it, the characteristic spectral lines of the metal. In all experiments made in this way, either air or another permanent gas occupied the space between the two extremities of the wires. The con- sequence of this is, the interposed gas partly conducting the electric current on its way through it, two spectra are obtained at the same time — the spectrum of the metal and the spectrum of the interposed gaseous medium. This inconvenience is the greater, as in most cases the number of bright lines constituting gas-spectra is a considerable one ; it is least in the case of hydrogen, the spectrum of which, if appearing under these con- ditions, becomes nearly a continuous one (59). If the substance submitted to experi- ment be not a metal or charcoal, the extremities of the metallic wires are to be covered with it. Then we get with the spectrum of the non-conducting substance at the same time the spectrum of the metal covered by it. 4. The spectra are obtained the most beautifully and are the most suitable for exami- nation in their minute details, if the substance be in the gaseous state before the electric discharge is sent through it. The spectral tubes for enclosing gas, first proposed and employed by one of us, were in most cases, with some modifications, adopted for our more recent researches. Our tubes, as represented by the diagram (fig. 1), gene- ^ rally consist of a capillary middle part 30-40 millims. long, and T5-2 millims. in diameter, forming a narrow channel, by which two larger spheres, with platinum electrodes traversing the -glass, communicate with one another. The small tube starting from one of the spheres serves to establish the com- munication with the exhauster, to which it is either attached by means of a cement (sealing-wax for instance), or soldered by the blowpipe. The ex- hauster, made solely of glass, without any metal, is connected with an addi- tional system of glass tubes and glass cocks, by means of which the spectral tube is most easily filled with the gas to be examined. If the gas be a per- manent one, the apparatus by which it is developed, and its accessory parts, by which it is purified and dried, may, as well as the spectral tube, simulta- neously and separately be evacuated. The gas arrives directly from the appa- ratus into the tube, which, ad libitum , may be alternately filled and ex- hausted again. Finally, the tension of the gas is regulated and measured by means of a manometer in connexion with the exhauster. 5. In order to compare with one another the spectra corresponding to different densities of the gas, or even to a mixture of different gases, the tube may be examined by the spectroscope while attached to the exhauster. But generally the spectral tube was blown off and hermetically sealed at the extremity of the narrow tube starting from one of the spheres. This tube equally serves to attach the spectral tube before the slit of the spectroscope. 6. If the substance submitted to examination were at the ordinary temperature in the liquid or solid condition, the tube destined to receive it was made of a glass diffi- SPECTRA OF IGNITED GASES AND VAPOURS. 3 cultly fusible, and bent as shown by the diagram (fig. 2). After having introduced into it a small quantity of the substance, the last traces of air were expelled from the tube, which was finally blown off. Put before the slit of the spectroscope, the enclosed substance was, by means of a lamp, reduced into vapour and, if necessary, kept in the gaseous state (fig. 3), and the density of the vapour regulated. The glass of our spectral tubes of this description is fused with such difficulty, that these highly evacuated tubes, when becoming red-hot by the lamp, are not altered by the pressure of the surrounding air. Fig. 2. Fig. 3. 7. Before giving a general account of the results we have obtained, it seems necessary to enter into some preliminary discussions regarding the admirable working of Geissler’s exhauster, and the phenomena shown by our tubes when highly evacuated by it. The essential part of Geissler’s exhauster is a large glass ball, containing ten to twenty kilogrammes of mercury, which in its upper part communicates, by means of a doubly perforated stopcock of glass, either with the free air, or with the spectral tube to be evacuated. From the lower part of the ball, which is invariably fixed, descends a longer tube of glass communicating at its lower extremity with a moveable similar tube, the free end of which enters into a large open bottle. When this bottle with the moveable tube is lifted up, the mercury within the apparatus entirely fills the ball, if commu- nicating with the air. This communication having been interrupted, a Torricellian vacuum is formed when the bottle descends. By establishing the communication with the spectral tube, the gas within it will be dilated. After the ascent and descent of mer- cury has thus been alternately produced often enough, no perceptible trace of air will remain within the spectral tube. 8. A tube evacuated in this way does not permit the induction current of Ruhmkorff’s smaller apparatus (which in air gives a spark of about 15 millims.) to pass through. The current of his large apparatus forces a passage ; but the spectrum we obtain in this case is very faint ; it shows no traces of the bands of nitrogen, but solely the lines of hydrogen and the large fields of vaporized carbon (51). The hydrogen-lines take their origin from hygroscopic water covering the interior surface of the spectral tube, the carbon-bands probably from the minute traces of fatty matter hitherto employed in b 2 4 DES. J. PLUCKEE AND J. W. HITTOEF ON THE greasing the stopcocks. (The oxygen simultaneously obtained by decomposition is not indicated.) The hydrogen-lines given by spectral tubes made of common glass are more brilliant than those of tubes made of less fusible glass, the hygroscopic state of the glass not being the same in both cases. Though within the interior of the exhauster the air is in contact with the surface of concentrated English sulphuric acid, or, what is preferable, with anhydrous phosphoric acid, we never succeeded in expelling the last traces of hygroscopic water, not even by strongly heating the spectral tube during evacuation. If, in the usual way, a Leyden jar be intercalated into the current of Ruhmkorff’s large induction coil, we must conclude, from the powerful charge of the jar, as proved by flashes of light, that within the spectral tube the tension of electricity, before it effects its passage, is very high. In this case the electric light is more bright, and of a fine colour like that of blue steel. When analyzed by the prism, it shows the spectral lines of hydrogen and oxygen, mixed with other spectral lines, among which those of sodium and silicium are the brightest. At the same time the interior surface of the capillary part of the tube tarnishes. Hence we conclude that the decomposed glass partly conducts the current. By means of our tubes, therefore, the theoretical conclusions of Dr. Faraday, that electricity being merely a peculiar condition of ponderable matter cannot exist without it, and cannot move without being carried by it, are confirmed and supported in a striking way*. 9. As soon as the tube encloses perceptible traces of air, the spectral lines resulting from the ingredients of the glass entirely disappear. Though the temperature of the gas be raised by the passing current to an immense height, nevertheless, on account of its great tenuity and the short duration of the discharge, the gas is not able to heat the surface of the glass sufficiently to volatilize it. In this case also no spectral lines owing to particles starting from the platinum electrodes appear in the capillary part of the tube. Those lines are to be seen only near the electrodes, namely, in the aureola surrounding the negative pole. 10. The temperature of the particles of air seized by the weakest electric spark by far surpasses the temperature of the hottest obtainable flame. For no flame whatever shows the spectral lines of air, which are constantly seen in the spark. In order to raise the temperature of the discharge of Ruhmkorff’s induction coil, you may either increase the power of the inducing current, or diminish the duration of the induced one. The last plan may be found preferable in most cases. The heat excited in a given conductor by a current sent through it increases in the ratio of the square of intensity, but decreases in the ratio of the duration of the current. Admitting, therefore, that the conductibility is not altered by elevation of temperature, and that the quantity of induced electricity remains the same, we conclude that the heating-power of the induced current is in the inverse ratio of its duration. But the resistance opposed by gases to the passage of * Mr. Gassiot has already obtained vacua so nearly perfect as to present an obstacle to electric conduction. See Philosophical Transactions for 1859, p. 148. SPECTRA OE IGNITED GASES AND VAPOURS. 5 electricity depends essentially upon their temperature. At the ordinary temperature it is rather too great to be measured, but, according to hitherto unknown laws, it rapidly decreases when the temperature rises beyond that of red heat. The law above men- tioned is therefore not strictly applicable in the case of gaseous conduction. 11. Electricity can only be discharged through a given stratum of air, from one point to another, after a certain electric tension takes place in these points. This tension depends upon the chemical constitution of the gas, and, the gas being the same, it is nearly in the ratio of its density and the distance of the two points. The quantity of electricity required to produce that degree of tension which must precede the electric discharge through our spectral tubes, enclosing gas of a given density, may be inde- finitely increased by interposing a Leyden jar. The less the distance between the coat- ings of the jar, and the larger their surface, the greater quantities of electricity will be accumulated on them, ready for discharge at the moment when the electric tension of the electrodes entering our tube reaches that intensity which alone allows the discharge to take place. Thus the Leyden jar is the most proper and most easy means for short- ening the duration of the discharge, and consequently increasing the temperature of the gas. In several cases, especially if a vapour like that of mercury be examined, which isolates less, it will be found more convenient, instead of replacing the Leyden jar by a larger one, to increase the charge of the same jar by intercalating into the circuit a spark micrometer, by means of which you may add to the resistance within the spectral tube the resistance of any stratum of air. 12. The leading idea by which one of us was guided when he first (1857) directed his attention to spectral analysis, was to concentrate the light in Geissler’s tubes by con- fining the electric current within a capillary channel *. The construction of our tubes immediately follows from it. Accordingly we gave, for different purposes, a different diameter to their capillary part. The length of this part is of very little influence if the tubes are very highly exhausted ; we had to shorten our recent tubes, intended to enclose gases and vapours of a greater density, rendered luminous by a powerful induc- tion coil. 13. We employed in our researches the large spectral apparatus constructed by M. Steiniieil. The refracting angle of one of the four flint prisms belonging to the apparatus is 60°, the angle of the three others 45°. Generally we made use of only two prisms (of 60° and 45°), and of a magnifying power of only 18. It is well known that the slit of the apparatus, if illuminated by sodium-light (by the flame of alcohol containing common salt), is seen double. According to the width of the slit and the dispersive power of the prisms, the two well-defined images, having both * Plucker : “ Spectra der elektrischen Licbtstromungen,” 30 Marz 1858, Poggendorff’s ‘ Annalen,’ vol. civ.; “ Ueber die Spectra der verschiedenen Gase, wenn durch dieselben bei starker Verdiinnung die elektriscbe Ent- ladung bindurchgebt,” 25 Aug. 1858, Ibid. vol. cv.; “ Ueber die Constitution der elektriscben Spectra von ver- scbiedenen Gasen und Dampfen,” 5 Mai 1859, Ibid. vol. cvii. 6 DRS. J. PLUCKER AND J. W. HITTORF ON THE the breadth of the slit as observed without the interposed prisms, are either superposed, or touch one another, or are separated by a black space. In making use of the two prisms, we generally regulated the aperture of the slit so that the two small sodium- bands appeared separated by a black space having nearly the breadth of these bands. In this case the angle at which the aperture of the slit is seen is equal to half the angu- lar distance of the two middle lines of the bands, and therefore equal to half the angu- lar distance of the two sodium-bands themselves after being reduced by narrowing the slit to mathematical lines. If the images touch each other, the aperture of the slit and the two sodium-lines are seen at the same angle. 14. The first fact which we discovered in operating with our tubes, guided by the above explained principles, was the following one : — There is a certain number of elementary substances , which , when differently heated , fur- nish two kinds of spectra of quite a different character , not having any line or any band in common. The fact is important, as well with regard to theoretical conceptions as to practical applications — the more so as the passage from one kind of spectra to the other is by no means a continuous one, but takes place abruptly. By regulating the temperature you may repeat the two spectra in any succession ad libitum. We will now treat more explicitly the case of Nitrogen , which first unfolded to us its different spectra. These spectra, obtained in the easiest and most striking way, have been examined by us in every point of view. The other cases of double spectra may hereafter be spoken of in a more summary manner. 15. We examined nitrogen prepared in different ways, even in the state of greatest purity ; but we found that, in order to get pure spectra of it, it was not necessary to free the gas from all traces of air *. Therefore we may select the following prepara- tion, imperfect as it is, in order to give an instance of constructing nitrogen-tubes. Three absorbing apparatus were connected with one another and, by means of a stop- cock, with the exhauster, the first two being filled with a solution of pyrogallic acid in hydrate of potash, and the third with concentrated sulphuric acid. After having evacuated the interior of the exhauster and the spectral tube connected with it, by care- fully turning the stopcock air was very slowly admitted, leaving its oxygen and carbonic acid to the first two, and its aqueous vapour to the third absorbing apparatus. Thus by and by the exhauster, with the tube, was filled with nitrogen, the manometer always indicating the tension of the gas. These operations being repeated several times by alternately evacuating and introducing new nitrogen, finally, the tension of the gas * Whatever may he, under certain conditions, the practical importance of prismatic analysis in detecting certain substances converted into vapour, whatever may be its use in indicating traces of a single gas imper- ceptible by other means, mixtures of permanent gases are not fitted to be examined by the prism. A gas, if mixed in rather small proportion with another one, entirely escapes observation. The proportion necessary to render it visible depends upon the nature of the gas as well as upon the temperature of ignition. SPECTEA OE IGNITED GASES AND VAPOUES. i (measured by means of the manometer) being from 40 millims. to 80 millims., the spec- tral tube was melted off and hermetically sealed. 16. When we send through our nitrogen-tube the direct discharge of Ruhmkorff’s large induction coil, without making use of the Leyden jar, we observe a beautiful richly coloured spectrum. This spectrum is not a continuous one, but divided into bands, the character of which differs essentially at its two extremities ; its middle part is in most cases less distinctly traced. Towards the more refracted part of the spectrum, the bands, illuminated by the purest blue or violet light, present a channeled appear- ance *. This effect is produced by a shading, the intensity of which decreases from the more to the less refracted part of each band. On applying four prisms instead of two, we perceive a small bright line, forming an interstice between two neighbouring chan- nels, and the shading is, by the telescope of the spectral apparatus, resolved into dark lines. The number of such dark lines of one of the brightest bands (of the eighth band, we always count from the red to the violet) was found to be thirty-four, or nearly so. Their mutual distance is nearly the same, but their darkness decreases towards the least- refracted limit of each channeled band. Hence we concluded, the breadth of the band having been measured, that the angular distance of two contiguous shading-lines was nearly equal to the distance of the two sodium-lines. The breadth of the channeled bands varies, but the character of all is absolutely the same ; only if foreign bright lines like those of hydrogen are simultaneously seen, it becomes slightly disturbed. We may distinguish seventeen bands of this description ; the first three are smaller ones, the fourth is traversed by H/3, the eleventh by Hyf. At the violet extremity the light is very faint. 17. The bands of the less refracted part of the spectrum are all of nearly the same breadth, but smaller than those just described, and of quite a different appearance. Making use of only a single prism, and of a small magnifying power, we count eighteen such bands, starting from the extreme red and extending to the greenish yellow, where they are bounded by a dark space. H a falls within the fourth, and the double sodium-line (Na) within the fourteenth of these bands. Under favourable circum- stances, both extremities of the spectrum being equally developed, these bands extend to the channeled part, their number rising to thirty-five. All have the same general character, but not the same brightness. From the extreme red the intensity of light * Under favourable conditions such a band appears furrowed semicircularly ; but psychological effects of this description may be quite different : partly by our own will, partly by exterior circumstances, the bands may be seen convex as well as concave. Even the engraving of the bands (Plate I.) shows it. Let it be illuminated by daylight through a window, you will see the bands concave if their more refracted and shaded part be directed towards the window ; if in the opposite direction, the bands will appear convex. The shade passes from one side to the other if really concave and convex bands are replaced by one another ; so it does if the illuminating light pass to the opposite side. Accordingly, the stereoscopic appearance depending upon the direction from which the light comes, the mind passes judgment on it unconsciously. t "We denote by Ha, H/3, and Hy the three bright lines of the spectrum of hydrogen (the red, the bluish green, and the violet one). See 57. 8 DRS. J. PLUCKEE AND J. W. HITTORF ON THE increases to the eighth band ; over the ninth, tenth, and eleventh, especially over the two last, a shadow is spread, which gives to the red a rather brownish tint. The next seven bands are of a fine orange and yellow colour. The nineteenth and twentieth bands are very dark, the twenty-first is less dark. The following bands have a green colour, varying in brightness. The darkest are the twenty-eighth and twenty-ninth, succeeding the lightest ones. The cause producing these bands and their shading by dark transverse lines is evidently not the same as that which produces the shadow overspreading some of them. This may be concluded, for instance, from the fact that the shadow which darkens the nineteenth and twentieth bands, without entirely destroying their limits, spreads at the same time over the neighbouring third part of the preceding eighteenth band. 18. When the light sent out from the incandescent nitrogen within the capillary tube is dispersed by means of four prisms, the shading of the less refracted bands also is resolved into dark narrow lines ; but these lines are smaller than the similar lines of the more refracted bands, and their distribution quite different. If the dispersion increase, in each band we at first perceive a new dark limit ; but the design becoming gradually more defined, we observe in each band extremely delicate bright lines bounded by a shadow or by dark lines. By closer examination of a band we distinguish first a least-refracted small part, occupying about the seventh part of the whole, formed by two bright lines including a somewhat larger dark space. The first of these two bright lines touches the dark extremity of the preceding band ; the second is bounded by a subtle dark line, to which succeeds a third bright line, smaller than the two first. A fourth bright line divides the whole band into two parts, one less refracted, comprising the small one just described, the other more refracted and larger — the breadth of the two parts being about in the ratio of 4 : 5. Starting from the bright middle line, a feeble shading is produced by a number of most subtle dark lines, the darkness of which decreases towards the least-refracted part. Similar but darker lines produce the stronger shading of the larger more refracted part, decreasing in the same direction from the extremity of the whole band towards its bright middle line. The stereoscopic effect produced by the shading of the bands is represented by the diagram (Plate I.). The configuration of all the bright orange and yellow bands is exactly the same ; it is rather obscured in the case of the preceding bands by the shadow spreading over them, but becomes the same again in the bright red ones. Even in the dark bands 19 to 21, traces of the design are to be seen. The appearance of the green bands, though the general character be the same, slightly differs ; the shading in the middle part of them being increased, they rather seem to be divided into two. The accordance of these bands, even to the minute detail of their configuration, is a fact worthy of attention. 19. The character of the two systems of bands on the extremities of the spectrum is SPECTEA OE IGNITED GASES AND YAPOUES. 9 entirely stereotype ; all apparent changes result from the different intensity of light. The middle part of the spectrum, on the contrary, may much differ from that which we have described ; you may even say that this part varies more or less essentially on replacing one spectral tube enclosing nitrogen by any other. Sometimes the traces of the less refracted bands are seen far beyond H/3, spreading over the channeled part of the spectrum ; in other cases the channeled appearance goes in the opposite direction as far as the sodium-line, disturbing the character of the bands. 20. Now, instead of the direct discharge of Ruiimkorff’s large induction coil, let us send through the very same spectral tubes the discharge of the interposed Leyden jar. The spectrum then obtained (Plate II.) has not the least resemblance to the former one. The variously shaded bands which we have hitherto described are replaced by brilliant lines on a more or less dark ground. Neither the distribution of these new lines nor their relative brightness gives any indication whatever of a law. Nevertheless the place occupied by each of them remains under all circumstances invariably the same. If exactly determined, not only does each line undoubtedly announce the gas within the tube, but the gas may even, without measuring, be recognized at first sight by charac- teristic groups into which the lines are collected. 21. The new spectrum of nitrogen extends towards the red slightly beyond the hydrogen-line Ha, which if the gas be not dried with care will be seen simultaneously, enclosed by two red nitrogen-lines, the less refracted of which is twice as distant as the more refracted. There are in the spectrum five groups of brilliant lines especially remarkable. The orange group, slightly less refracted than Na, is formed by four lines, the second of which is the brightest ; the third, not quite so bright, is closely followed by the fourth, which is very faint. The second (yellow) group contains seven lines, among which the fifth is brightest. The third (light-green) and the fourth (dark-green) group contain each nine lines. The third and sixth lines of the light-green group and the sixth and seventh (both near to each other) of the dark-green group are brightest. The fifth (light-blue) group (the distance of its middle part from H/3 and Hy is about in the ratio of 3 : 4) is formed by six lines, the second of which is the brightest, the first slightly less bright ; the last four lines, nearly equally distant from each other, are slightly less bright again. Two groups, of three fainter lines each, fall between the two green groups and between the dark-green and the blue. We may mention also two bright single lines, placed out of the groups — a green line preceded by an expanded one, and a light-violet line followed at a short distance by a bright band. Besides, there are in the spectrum more or less faint bands or expanded lines extending beyond Hy nearly as far as the distance between this line and H/3, i. e. about to Fraunhofer’s line H. 22. We may denote the orange, yellow, light-green, dark-green, and blue groups by I, ii, hi, iv, and v, and the single lines of them by the arabic numbers, the place they occupy in each group being reckoned from the less to the more refracted. Thus by adding the chemical symbol of the gas we get a general method of denomination, mdccclxv. c 10 DBS. J. PLUCKER AND J. W. HITTORP ON THE according to which N n 5, N iv 6, N iv 7, and N v 2, for instance, indicate the brightest lines of the groups of the nitrogen-spectrum. 23. Not only is the general character of the two kinds of spectra we obtained when nitrogen was heated in our tubes, either by the direct discharge or by the discharge of the interposed Leyden jar, quite different, but the difference is even so great that the bright lines of one of the spectra do not in the least fall within the brighter part of the bands constituting the other. Thus, for instance, the bright yellow line (N ii 5) falls within the nineteenth band, the darkest of all the bands constituting the less refracted part of the spectrum ; the bright blue line (N v 2) falls into the darker part of one of the channeled spaces. Accordingly it appears by no means probable that by increasing the temperature the shaded bands of one spectrum may be transformed gradually into the bright lines of the other ; nevertheless it would be desirable to prove by experiment that the passage from one spectrum to another is a discontinuous and abrupt one. 24. For a given nitrogen-tube which without the Leyden jar gives the spectrum of bands, and by means of the commonly used jar the spectrum of bright lines, you may easily select a jar of smaller covering, which, if intercalated, exhibits the curious phe- nomenon of two rival spectra disputing existence with each other. Sometimes one of the spectra, sometimes the other appears ; and for moments both are seen simultaneously. Especially the brighter lines of the second spectrum abruptly appear in the blue and violet channeled spaces of the first, and, according to the fluctuation of the induced current, either suddenly disappear again or subsist for some time, and constitute with the added fainter lines the second spectrum. We obtain in an easier and a continuous way both spectra simultaneously by making use of a small Leyden jar, and increasing its charge by an intercalated stratum of air the thickness of which increases till the bright lines appear within the bands of the primitive spectrum. 25. By these and other experiments it is evidently proved that ignited nitrogen shows two quite distinct spectra. Each bright line of one of these spectra, each of the most subtle lines into which, by means of the telescope, the bands of the other are resolved, finally depends upon the molecular condition of the ignited gas, and the corresponding modification of the vibrating ether within it. Certainly, in the present state of science, we have not the least indication of the connexion of the molecular constitution of the gas with the kind of light emitted by it ; but we may assert with confidence that, if one spectrum of a given gas be replaced by quite a different one, there must be an analogous change of the constitution of the ether, indicating a new arrangement of the gaseous molecules. Consequently we must admit either a chemical decomposition or an allo- tropic state of the gas. Conclusions derived from the whole series of our researches led us finally to reject the first alternative and to adopt the other. 26. The same spectral tube exhibits, in any succession whatever, as often as you like, each of the two spectra. You may show it in the most striking way by effecting the intercalation of the Leyden jar by means of a copper wire immersed in mercury. As SPECTEA OE IGNITED GASES AND VAPOURS. 11 often as the wire is taken out of the mercury we shall have the spectrum of bands ; as soon as the communication is restored, the spectrum of bright lines. Hence we con- clude that the change of the molecular condition of nitrogen which takes place if the gas be heated beyond a certain temperature by a stronger current, does not permanently alter its chemical and physical properties, but that the gas, if cooled below the same limit of temperature, returns again to its former condition. 27. The essentially different character of the two extremities of the first spectrum of nitrogen, as described (16-19), and the indistinctness of its middle part, suggested to us the idea that, in reality, the observed spectrum might originate from the superposition of two single spectra. Accordingly one of these single spectra, the more refracted part of which is best developed, must be formed by channeled spaces ; the other one, the less refracted part of which is best developed, must be a spectrum of shaded bands. In different cases, either the one or the other of the spectra may be predominant. In order to confirm our conjecture it was necessary to get the two spectra separated. 28. The discharge of Ruhmkorff’s coil through a spectral tube is changed the less by introducing the Leyden jar, the weaker is the resistance opposed to it by the tube. Accordingly the two different degrees of temperature to which the gas rises by the discharge when, the coil remaining the same, we either make use of the jar or not, may be regulated in such a way as to approach one another more and more. Let the tension of the gas of about 10 millims. remain the same, the temperature produced by the discharge will be diminished by increasing the interior diameter of the capillary part of the spectral tube. Thus we succeeded in constructing a tube which, when the direct discharge was sent through it, became incandescent with the most brilliant gold- coloured light, which might easily be confounded with the light of highly ignited vapours of sodium ; but with the intercalated jar, the light of the incandescent gas within the same tube had a fine bluish-violet colour. The yellow light, when analyzed by the prism, gave a beautiful spectrum of shaded bands, extending with decreasing intensity to the blue, the channeled spaces being scarcely perceptible. The bluish light, when examined, was resolved by the prism into channeled spaces extending towards the red, while the former bands almost entirely disappeared. We may transform each colour and its corresponding spectrum into the other ad libitum. Hence it follows that there is another allotropy of nitrogen, which, like the former, is not a stable and permanent one, but depends only upon temperature. The modification in which nitrogen becomes yellow corresponds to the lower, the modification in which it becomes blue to the higher temperature. 29. When we send the direct discharge of Ruhmkorff’s coil through one of Geissler’s wider tubes enclosing very rarefied nitrogen or air (the oxygen of air becomes not visible here), we see the negative pole surrounded by blue light, the light at the positive pole being reddish yellow. In such of Geissler’s tubes as are especially calculated to show how the light starting in all directions from the different points of the negative elec- trode is by the action of an electro-magnet concentrated along the magnetic curves c 2 12 DBS. J. PLUCKER AND J. W. HITTORF ON THE passing through these points, the blue light is most beautiful. It belongs generally to the nitrogen alone, which, on account of the greater resistance at the negative electrode opposed to the discharge, reaches a higher intensity of heat there than at the positive pole. When analyzed by the prism, the blue light gives the spectrum of channeled spaces, with traces only of the less refracted bands. The reddish-yellow light of the positive pole is more faint, and therefore not so easy to be submitted to spectral analysis. 30. When Ruhmkorff’s large induction coil is discharged in common air between two points the distance of which does not exceed a few centimetres, we obtain, as is well knoAvn, a brilliant spark surrounded by an aureola, the colour of which is partly bluish violet, partly reddish yellow. In order to separate these colours more distinctly from each other, the aureola, moved by the slightest breath, may be extended into a large surface by blowing it sideways. But the separation may be best made when the dis- charge takes place between the two poles of an electro-magnet in the equatorial direc- tion. While the straight spark is not acted upon by the electro-magnet to any sensible degree, the aureola is expanded into a fine surface, bounded by the spark starting from one to the other extremity of the electrodes, and by a semicircle passing through these extremities. At a certain rarefaction of air this surface appeared most beautifully bounded by a semicircular golden-coloured band, and divided by a similar band into two parts*. We may explain now in a satisfactory way the appearance, hitherto mysterious, of the golden light. Both the yellow and the blue light are owing to the nitrogen of the air, reduced by the heat of the current into the two allotropic states which exhibit the spectra of channeled spaces and of bands. The brilliant white light of the spark partly belongs to the oxygen, partly to the nitrogen of the air, both highly ignited, the nitrogen being in that allotropic state in which it exhibits the spectrum of bright lines. 31. In order to complete the history of the spectrum of nitrogen we add two remarks. First, by intercalating a Leyden jar and, in order to weaken the current, at the same time a stratum of water or a wet thread, we may also reduce the spectrum of bright lines to the spectrum of bands. Secondly, by increasing the density of the gas, or, if the gas be less dense, by intercalating at the same time a large jar and a stratum of air, the bright lines of the spectrum, at the highest obtainable temperature, will expand. Out of a great number of observations made in this direction we shall describe only one. 32. A short spectral tube enclosing nitrogen of a tension of about 250 millims. refused passage to the discharge of Ruhmkorff’s large induction coil, when three of Grove’s elements were made use of and the jar intercalated. Without the jar the discharge passed through and produced a bright but rather undefined spectrum of bands. When the current continued to pass, the indistinctness of the spectrum in- creased, and after short intervals brilliant coloured lines appeared and disappeared again, like lightning-flashes. These lines, occupying always the same place, belonged to the second spectrum of nitrogen, the brightest yellow and green lines of which * Pll'cker, “TTeber die Einwirkung desMagnetes auf die elektrische Entladung,” Poggendohff's ‘Annalen,’ vol. cxiii. p. 267. SPECTRA OF IGNITED GASES AND VAPOTJRS. 13 (N ii 5, N iv 6, N jv 7) were specially observed. When we made use of twelve of Grove’s elements ranged into three sets of four combined ones, the current even passed after we interposed the Jar, and we got a most dazzling second spectrum of the gas. The bright lines of this spectrum, rising from a ground itself brighter than it usually is, ceased at an increased brilliancy to be well defined. The two brilliant green lines both expanded, and were united into a single broad line ; the double yellow lines, though expanded, yet remained double. The spectrum was progressing towards a continuous one . 33. In recapitulating, we get the following results: — Nitrogen in the state of greatest rarefaction, such as may be obtained by Geissler’s exhauster, like other gases does not allow the induction current to pass through. But when its tension is only a small fraction of a millimetre, the current begins to pass and renders the gas luminous. Below a certain limit of temperature ignited nitrogen sends out a golden-coloured light, giving the spectrum of bands. Above this limit the colour of the light is replaced by a bluish violet, the spectrum of channeled spaces replacing simultaneously the spectrum of bands. When, by means of the intercalated jar for instance, the temperature rises to a second higher limit, the light of the gas, becoming white and most brilliant, gives, if analyzed by the prism, a spectrum of quite a different description : bright lines of different intensity, with the colour indicated by the place they occupy, rise from a dark ground. By increasing the power of the discharge these lines become more brilliant, but the brilliancy does not increase in the same ratio for them all. New bright lines appear, which formerly, on account of their extreme faint- ness, were not visible ; but the number of such lines is not unlimited. By increasing the heat of the ignited nitrogen to the last extremity, the lines, especially the brighter ones, gradually expand, approaching thus to a continuous spectrum. 34. Those spectra which are composed of larger bands showing various appearances according to their being differently shaded by subtle dark lines , we generally call spectra of the first order. In the same spectrum the character of the bands is to a certain extent the same, the breadth of the bands varies in a more or less regular way. On the con- trary, those spectra in which brilliant coloured lines rise from a more or less dark ground, we call spectra of the second order. Ignited nitrogen therefore exhibits, if its temperature increase, successively two spectra of the first and one of the second order. 35. In the case of sulphur, which we may select as another instance, there are two different spectra, one of the first and one of the second order. In common air the flame of sulphur gives a continuous spectrum ; if fed with oxygen we get a spectrum of the first order, but it is faint and its bands are not well defined. In order to get the sulphur-spectrum most perfect, we must recur to our spectral tubes. A doubly bent short tube (6), into which we introduced a small quantity of sulphur, was evacuated by means of Geissler’s exhauster, and while attached to it heated by a lamp, in order to expel as much as possible the moisture it contained. Finally, the mano- meter showing no more tension of the remaining gas, the tube was hermetically sealed 14 DES. J. PLtJCKEE ANT) J. W. HITTOEF ON THE by a blowpipe. The direct charge of Ruhmkorff’s large induction coil sent through it, generally indicates by their spectra traces of remaining foreign substances (8). But when the tube was heated by a small alcohol-lamp, at a certain moment a fine sulphur- spectrum of the first order appeared, undisturbed by any former spectrum. The beauty of the spectrum increased when we continued to heat moderately. 36. We counted thirty-seven well-defined bands, extending nearly from Ha to Hy. Seven of these bands, the first of which was of a dark-red colour and visible only under favourable circumstances, preceded the sodium-line, eighteen fell between this line and H/3, and eleven between H/3 and Hy, the last of which being broader, appears some- times divided into two. After a last band, traversed by Hy, a larger and strongly shaded space extended towards the extreme violet. The breadth of the bands increased from the less to the more refracted part of the spectrum. In each band, contrary to what takes place in the case of nitrogen, namely, with regard to its chan- neled spectrum, the shading produced by fine dark lines decreases from the less to the more refracted extremity. The darkest part of the shadow is bounded by a small sepa- rate band of a varied appearance, generally formed by two small bright lines including a somewhat larger dark one. By these small bands the purely channeled character of the spectrum is disturbed. 37. If, while the discharge is passing, we continue to heat the tube by a lamp, the brightness of the spectrum always increases ; but if we approached to a certain degree of temperature, in different parts of the spectrum we have described, bright-coloured lines belonging to the sulphur-spectrum of the second order appeared and disappeared again according to the fluctuating heat, till at last the second of the two rival spectra remained undisturbed. The colour of the light was changed. In cooling again after the lamp was taken off, the light within the tube changed its colour again, while the spectrum of the second order was replaced by the spectrum of the first order. There is a certain elevation of temperature at which the increased density of the vapour does not permit the discharge to pass ; the light within the tube is extinguished, but abruptly reappears after cooling. 38. Well-defined bright lines, constituting a fine sulphur-spectrum of the second order, are obtained if moderate discharges of Rhumkoeff’s large induction coil are sent through the tube, the tube being slightly heated by means of an alcohol-lamp, and a small Leyden jar being intercalated. At first the spectrum extends only from about the sodium-line to H/3. One observes chiefly a characteristic group of sixteen lines, followed at some distance by two separate lines. The spectrum once developed persists even after taking off the lamp. When we continue to heat, the brightness of the group increases and its lines begin to expand, while at the same time the hitherto black ground is coloured. The brilliancy may be increased to such an extent as to be unbearable to the eye. Beyond the sodium-line, towards the red extremity, new distinct lines appear, among which we particularly distinguish a triple line, remarkable as well for its fine red colour as for its distinctness, and nearer to Ha a second such triple line, at first well SPECTEA OF IGNITED GASES AND VAPOUES. 15 defined but soon merging into a single one. Like the less refracted part of the spec- trum, the most refracted part is developed only at a higher ignition of the vapour of the sulphur. At its violet extremity (we do not give here a full description of the middle part) we observe at the same distance from one another five well-defined fainter bright lines. Then follows, after an expanded violet band, a group of four bright lines, the second of which is accompanied by a more refracted, the fourth by a less refracted faint line. The fourth line especially is distinct to a degree seldom observed at so high a refraction and so great a power of the discharge. After two bands of faint light, there is seen at the end of the spectrum a group of four slightly expanded bright lines, preceded by an expanded violet band. 39. Like sulphur, selenium has two spectra — one of the first, another of the second order. 40. Ignited carbon, even in a state of greatest division, gives a continuous spectrum. 41. We select, among the various compound gases which, if decomposed in flame, give the spectrum of carbon, in the first place cyanogen. The gas was procured by heating cyanide of mercury introduced into a retort of glass by means of a lamp. The flame of it may be fed either with oxygen or with air. When a jet of cyanogen mixed with oxygen is kindled, in the interior part of the flame a most brilliant cone of a whitish-violet light is seen, the limit between the ignited and the cold part of the jet. This cone exhibiting the spectrum of vapour of carbon best developed, we conclude that the cyanogen must be decomposed into carbon and nitrogen, the carbon being in the gaseous condition a moment before its combination with oxygen takes place*. 42. In order to prevent explosion of the mixture of cyanogen and oxygen, it is pre- ferable that the jets of the two gases meet from opposite sides before the slit of the spec- tral apparatus, forming there, if kindled, a brilliant, flat, vertical surface. The jet of cyanogen might be obtained directly from the retort, by the heating of tvhich it may be regulated. Thus we get, all being properly arranged, a splendid and richly coloured spectrum. Especially we distinguish eight groups of bright lines , which, being all of the same general character, indicate at first sight the existence of vapour of carbon. We shall denote these groups, starting from the less refracted and proceeding to the more refracted ones, by a, b, c, d, e, f, g , h. The group a is formed by five, b by six, c by four, d by five, e by seven, f by three, g by seven, and h by three bright lines. But these lines, of a measurable breadth and a quite different appearance, are not to be confounded with the bright lines which, in the case of nitrogen and sulphur, for instance, constitute spectra of the second order. In each group the first line is the brightest ; the following, which are nearer to one another, decrease in intensity, and under less favourable circum- stances the last ones are not seen. Hence the groups, according to an expression of Mr. Attfield, have the appearance of a portico. The red group (a) is not always seen distinctly (less distinctly in the present case than in the case of other gaseous com- * Mr. Attfield has the merit of haying first stated that spectra hitherto attributed to compound gaseous substances, are to he referred to the vapour of carbon itself (Philosophical Transactions for 1862, p. 221). 16 DES. J. PLtJCKEE AND J. W. HITTOEF ON THE pounds of carbon) ; the group f is very faint, the group g beautifully violet, h rather ultra-violet. 43. The whole spectrum, except its red extremity, is divided into large shaded fields. The shadow increases from the less to the more refracted part of each field ; from its Drighter less refracted part arise the bright lines of one group, the first of these lines towards the darkest extremity of the preceding field. As well as in the former cases of nitrogen and sulphur, the shadow is produced by dark transversal lines on a coloured ground. But here the distance of the shading-lines from each other varies even in the same field. Towards the bright, i. e. the less refracted extremity of each field, the distance decreases, while at the same time the darkness and the breadth of the lines is diminished. The space between two consecutive lines appeared to be greatest in the field containing the group c, at a distance from d about twice as great as that from c. There we counted, on making use of two prisms and applying a magnifying-power of eighteen, the aperture of the slit being regulated in the ordinary way (13), nine shading- lines, including eight nearly equal small bands, the total breadth of which corresponded to five divisions of our arbitrary scale. Hence we computed the angular distance of two consecutive dark lines which we observed to be about five-fourths of the distance of the sodium-lines. The dark shading-lines also appear within the bands bounded by the lines of the brighter characteristic groups. The band between the second and the third bright line of the yellow group b, the total breadth of which corresponds to four divisions of our arbitrary scale, was divided by dark lines into twelve smaller bands of about equal breadth. Accordingly the angular distance of two such consecutive lines is about two- thirds the distance of the two sodium-lines. The dark lines within the neighbouring band, bounded by the first and second bright line of the same group, were much nearer to one another, and their number too great to be counted with certainty. 44. Between the groups f and g there is indicated a particular distribution of light and shadow, which, being a faint copy of what takes place if olefiant gas be burned instead of cyanogen, will be better understood after we have described the spectrum of the new gas. 45. The least-refracted part of the spectrum, preceding the first line of the group a , essentially differs from the more refracted part already described. There are three fine red bands contiguous to the first bright line of the group, extending nearly to Ha, and beyond this hydrogen-line, after a dark space, two similar but not so well-defined bands. The breadth of these bands is nearly the same, and all are shaded in a similar way. Contrary to the distribution of shadow in the larger field, the shadow is strongest in the less refracted part of each band ; in the most refracted part we observed two bright lines. 46. When the combustion of cyanogen took place in air, the bands we have just described were best developed, and new similar ones added. They extended from beyond Ha nearly to H/3. The breadth of these bands slightly increases towards the violet end of the spectrum, their general description remaining the same. We especially counted seven such bands, the first of which is traversed by the double sodium-line, and the last SPECTEA OF IGNITED GASES AM) VAPOURS. 17 is bounded at the place formerly occupied by the second bright line of the character- istic group c. When the flame of cyanogen is fed by air, we observe under favourable circumstances no traces of the groups a and b, the least-refracted bright line of the group c faintly appears, d is scarcely indicated, but the groups e , f, g are fully developed, especially the last one, of a fine violet colour. 46. In supplying the flame of cyanogen by air increasingly mixed with oxygen, we distinctly see two spectra overlying one another. One of these spectra (the spectrum of bands) giving way step by step to the other, the appearance is continually changed. The red bands only remained undisturbed, they became even more distinct by the increased intensity of the combustion. The adjacent group a is scarcely developed, evidently on account of an imperfect extinction of the overlying bands. The superposition of the two spectra introduces new details into the general configu- ration of the resulting spectrum. Thus, for instance, at a certain intensity of combus- tion the interval between the first and second bright line of the group b is divided by four fine bright lines into five spaces, the breadth of which decreases towards the violet part of the spectrum. Thus also in the large field containing the group c, the influ- ence of the spectrum of bands is rendered sensible by a particular distribution of shadow. 47. Secondly, we submitted to a closer examination olefiant gas, H4 C4, when burned either with oxygen or with air. We operated as we did in the former case of cyanogen ; only the gas, prepared by heating a mixture of alcohol and sulphuric acid, was previ- ously introduced into a gasometer. The luminous cone which exhibits the spectrum of vapour of carbon is of a fine blue colour, especially if the flame is fed by oxygen. 48. In the spectrum thus obtained the characteristic groups a, b, c, and d appeared on a shaded ground. All these groups, especially the red one a, scarcely seen in the spectrum obtained by the combustion of cyanogen, are finely developed. The last line of b and d is slightly expanded ; but there is no trace whatever either of the bands of the spectrum of cyanogen, if burned in common air, or even of the groups e and g. Instead of these groups there is quite a new configuration. Equally distant from the place which the groups occupied in the former spectrum, a small well-defined black band was seen, bounded on the more refracted side by a violet space, which, being of great brilliancy where it touches the band, was shaded gradually till the spectrum, not extending beyond the place of the group g , was extinguished. This violet space is tra- versed by well-defined dark lines, equally distant from each other, but more apart than the shading lines we described in former cases. The black band is bounded on its less refracted side by a bright line, having the breadth of the lines of the characteristic groups, which at a certain distance was preceded by a more diffused violet light, tra- versed, like the brilliant one on the opposite side, by dark but less distinct lines. Here also the faint group f appeared. The distribution of light and shade producing the configuration just described i& MDCCCLXV. d 18 DRS. J. PLtJCKER AND J. W. HITTORF ON THE seen also, distinctly but faintly, in the spectrum we obtained by the combustion of cyanogen with oxygen, where at the same time the groups e and g are beautifully expressed (44). 49. Among the gases exhibiting the spectrum of vapour of carbon, when enclosed in our spectral tubes and decomposed by the heat of the discharge of Ruhmkorff’s coil, we first select oxide of carbon. In operating with this gas as we did with nitrogen, we got, if the Leyden jar was intercalated, simultaneously the spectrum of vapour of carbon and the spectrum of oxygen ; without the jar, the pure spectrum of vapour of carbon. In the last case the heat of the discharge is high enough to ignite vapour of carbon, but not sufficient to give the spectrum of oxygen. The single spectrum, as well as the combined one, is obtained accordingly ad libitum ; whence we conclude that as the successive discharges pass through the spectral tube, the gas is alternately decom- posed and recomposed again. 50. We shall in a few words describe the spectrum obtained without the jar, at a ten- sion of the gas, when observed by means of the manometer before the spectral tube was sealed, of 32 millims. Four characteristic groups only were seen, a, b , c, and d. When the current first passed, the band a appeared completely ; after some time its two first lines only remained, rising as isolated bright lines from a dark ground ; finally all the group dis- appeared. The groups b, c, and d remained nearly unchanged ; there appeared only two bright lines of c , the place corresponding to the two following ones being very brilliant. The whole spectrum was divided into large fields, similar to the fields we described in the case of the flame of cyanogen fed with oxygen. But in this case each field is bounded at its more refracted and shaded extremity by the first bright line of a charac- teristic group ; the following lines, bordered by shading, rise from the lightest part of the adjacent field. In the new instance the fields are not bounded in the same way. After the group a has disappeared, there is a differently shaded dark space, extending to the place of the third bright line of that group. In the remaining part of the spec- trum we may distinguish seven shaded fields. The first goes a little beyond the first bright line of the group 5, where it is bounded by a transversal line, dividing the band formed by the first two lines of the group into a dark less refracted and a light more refracted part. Accordingly the first bright line rises from the dark end of the first field, the remaining lines from the light end of the second field. The second field does not reach the first bright line of the following group c , this line being nearly equally distant from the extremity of the field and the next line of the same group. The third field goes slightly beyond Hp ; the fourth to the first line of the group d ; the fifth nearly to the place occupied by the fifth line of the group e ; the sixth approaches the place of the group/; and the seventh extends to the fourth line of the group g. The fourth and sixth fields presented the appearance of pure channeled spaces, as described in the case of nitrogen. SPECTRA OF IGNITED GASES AND VAPOIJES. 19 51. If the heating-power of the discharge be too strong, spectral tubes enclosing oxide of carbon at a higher tension showed only three large shaded fields, without any traces of the characteristic groups. The first two of these fields are coincident with the second and third of the former fields ; the third occupies the place of the fourth and fifth former fields united into one. Here the shading of the three large fields not being disturbed by any additional appearance, the transversal shading lines were observed most distinctly even in making use of four prisms and employing a magni- fying power of 36. In observing especially the light and less refracted part of the first field close to its extremity, these lines, on account of their extreme subtleness, are scarcely to be perceived ; when they begin to become well defined they are very near to each other; but towards the more refracted part of the field their distance increases simultaneously with their breadth, till, at some distance from the bright extremity, the dark expanded lines are resolved into small shaded bands*. 52. Spectral tubes containing carbonic acid instead of oxide of carbon gave essen- tially the same spectra. The increased quantity of oxygen of the decomposed gas may be observed by means of the interposed jar. In such tubes there was no carbon depo- sited, not even after a long passage of the discharge. 53. All compound gases enclosed in our spectral tubes are decomposed by the heat produced by the discharge of Ruhmkorff’s large induction coil ; but instantly after the discharge passes, the recomposition takes place. The recomposition is prevented only by a sudden cooling of the elementary gases obtained by the decomposition. Thus, for instance, spectral tubes enclosing cyanogen are scarcely fitted for observation, the inte- rior surface of their capillary part being instantaneously blackened by the deposited carbon. No carburetted hydrogen resists final decomposition by the passing current. We add only a few observations, made by means of spectral tubes. 54. The spectrum of the light hydrocarbon gas, C2 H4, obtained without the Leyden jar, at once showed the expanded bright lines of hydrogen and an imperfect spectrum of vapour of carbon, especially the brightest lines of the characteristic groups b , c, and d. By intercalating the jar, the hydrogen-spectrum, approaching to a continuous one, became quite predominant. Olefiant gas , C4 H4, of a primitive tension of about 70 millims., gave, without the jar, a scarcely visible spectrum ; by intercalating the jar, the three hydrogen-lines Ha, H/3, Hy appeared well defined, and the spectrum of vapour of carbon, with its groups a, b, c , d , and its shaded large fields, well developed. Methyl , C2H3, showed, without the jar, at once Ha, H/3, Hy, and the characteristic groups e and g ; with the interposed jar these two groups disappeared, and were replaced by the groups a, b, c, and d. Acetylene, C4 H2, though according to Berthelot and Morren formed from its * The same spectrum, but fainter, is obtained under quite different conditions. We have already noticed, in the introductory remarks, that in a spectral tube evacuated to the last degree by Geissler’s exhauster, vaporized carbon is indicated by its spectrum. The spectrum obtained is that described above (8). D 2 20 DES. J. PLUCKEE AND J. W. HITTOEF ON THE elements when Davy’s charcoal light is produced within an atmosphere of hydrogen, when introduced into our tubes is nevertheless rapidly decomposed by the discharge, and most incompletely recomposed after the discharge has passed. The inside of the tubes is instantly blackened, and in the first moment only, along with the spectrum of hydrogen, we perceive the groups of carbon-lines seen in the case of olefiant gas. 55. Finally, Ruhmkorff’s large induction coil was discharged between two electrodes of carbon, surrounded by an atmosphere of hydrogen. The four groups a , b, c, and d were obtained, constituting the spectrum of vaporized carbon. 56. In resuming, we are struck by the variety of appearances presented by ignited vapour of carbon when submitted to spectral analysis under different conditions. But, whatever may be this variety, it is impossible not to admit that all or nearly all of the various types of spectra we described are derived from the same source. We may distinguish four such types : 1st, the bands, especially seen when the flame of cyanogen is fed by air ; 2ndly, the particular distribution of light and shadow near H|3 when the flame of olefiant gas is fed by oxygen ; 3rdly, the large fields shaded by transversal dark lines ; 4thly, the characteristic groups of bright lines, a, b, c, d, e, f, g, h , which are to be ranged into two different sets, a, b , c, d, and e, f, g, h. It is a curious fact that all these different types, either fully developed or indicated only, are represented in the flame of cyanogen, if fed with oxygen, while in all the other cases we examined there are represented either a single type or two types, or even three, — namely, 1, the third type alone ; 2, the first type, with the second set of groups ; 3, the third type, with one set of groups (a, b , c, d) ; 4, the same type, with the other set ( e , g) ; 5, the second and third types, with the first set of groups. There is no doubt that the different types correspond to different degrees of temperature, — the temperature being lowest when the bands are principally developed, lower in the case of the second set of groups than in the case of the first, lower in the case of the shaded large fields than in the case where the characteristic groups appear simultaneously. In the present state of the question we are not able fully to explain the various types of spectra of carbon. It is only proved that all spectra which we referred to carbonic vapour do not contain any bright line belonging to another elementary gas. Either the well-known spectra of foreign admixed gases, of nitrogen, oxygen, hydrogen, for instance, do not appear at all ; or if they do, they may be subtracted from the whole apparent spectrum. It appears doubtful that the different types depend solely upon temperature. If so, the temperature varying in the different parts of the ignited vapour of carbon, different types may be seen simultaneously. We shall not now discuss the influence which the coexistence of foreign gases might have on the spectra of vapour of carbon, nor may we here decide whether or not, in the lower temperature of the flame, a gaseous compound of carbon, not being entirely decomposed, exhibits, with the spectrum of the vapour of carbon, simultaneously the spectrum of the undecomposed gas. In the spectrum of cyanogen, for instance, we got no visible traces of the spectrum SPECTEA OF IGNITED GASES AND VAPOUES. 21 of nitrogen (originating from the decomposed gas), whether we supplied the flame by a jet of oxygen, or operated in open air; but in both cases there is no reason not to admit that the bands, which are not seen in the case of any other compound of carbon, were owing to the undecomposed cyanogen (see no. 61). 57. With regard to the spectrum of hydrogen , we first refer to former observations. The spectrum one of us obtained by sending the discharge of Ruhmkorff’s small induction coil through one of his highly evacuated spectral tubes, constructed by M. Geissler, shows only three bright lines, which he denoted by Ha, H/3, and Hy. The beautiful red light of the ignited rarefied gas, divided into these three bright lines, even after having passed through the four prisms of Steinheil’s spectral apparatus, remains highly concentrated. At a magnifying power of 72, the three bright lines or small bands thus obtained are well defined. Their apparent breadth is equal to the breadth of the slit ; consequently, on further narrowing the slit, they approach gra- dually to mathematical lines. Hence we conclude that, under the above-mentioned conditions, the length of wave of the light constituting each of the three hydrogen-lines is constant, and remains so if by widening the slit the lines are expanded into bands. In referring the middle lines of such bands to the middle line of the direct image of the slit, we obtain its angle of refraction. It was proposed to employ these middle lines instead of Fraunhofer’s dark lines of the solar spectrum in determining the indices of refraction*. This proceeding has since been proved to be very expedient f. 58. Hydrogen permits the electric discharge to pass at a lower tension than other gases do. When Ruhmkorff’s small induction coil was discharged through a spectral tube enclosing hydrogen, which was gradually rarefied to the highest tenuity to be reached by means of Geissler’s exhauster, finally the beautiful red colour of the ignited gas became fainter, and passed gradually into an undetermined violet. When analyzed by the prism, Ha disappeared, while H/3, though fainter, remained well defined. Accordingly light of a greater length of wave was the first extinguished $. 59. Hydrogen shows in the most striking way the expansion of its spectral lines, and their gradual transformation into a continuous spectrum. When the direct discharge of Ruhmkorff’s large induction coil is sent even through the old spectrum tubes enclosing hydrogen, the formerly obtained spectrum is essentially altered. By increas- ing the power of the coil, the violet line Hy first expands ; while it continues to expand, the expansion of the bluish-green line H/3 becomes visible. Let the aperture of the slit be regulated so that the double sodium-line will separate into two single lines nearly touching one another. Then, the angular breadth of H/3 becoming two or three minutes, the breadth of Hy is about double. The expansion takes place as well * Poggendorff’s * Annalen,’ vol. cvii. p. 497. t Landolt: “Ueber die Breehungsexponenten flUssiger homologer Verbindungen,” Poggendorff’s ‘Annalen/ vol. cxvii. p. 353. t Plucker : “ Ueber recurrente Strome und ihre Anwendung zur Darstellung von Gasspectren,” Poggen- dorff’s * Annalen/ vol. cxvi. p. 51. 22 DES. J. PLtJCKEE AND J. W. HITTOEE ON THE towards the less as towards the more refracted part of the spectrum. Ha remains almost unchanged after H y has passed into an undetermined large violet band, and H/3 extended its decreasing light on its two sides. On employing the Leyden jar, and giving to the gas in our new tubes a tension of about 60 millims., the spectrum is already transformed into a continuous one, with a red line at one of its extremities. At a tension of 360 millims. the continuous spectrum is highly increased in intensity, while the red line Ha, expanded into a band, scarcely rises from it. If the electric spark passes through hydrogen at the ordinary tension, the ignited gas on its way always gives the spectrum of the three expanded lines*. 60. Even in the old spectral tubes enclosing highly rarefied hydrogen, the ground, from which the three characteristic lines rise, did not appear always of the same dark- ness ; in some instances new bright lines appeared, especially in the neighbourhood of the sodium-line. In resuming the subject, we pointed out the existence of a new hydrogen-spectrum , corresponding to a lower temperature, but having no resemblance at all to the spectra of the first order of nitrogen, sulphur, &c. In this spectrum, of a peculiar character, if fully developed, we observe a great number of well-defined bright lines, almost too numerous to count and represent by an engraving, but brilliant enough to be examined at a magnifying power of 72, after the light has passed through four prisms. * After Fraunhofer, and especially Dr. Wheatstone, directed the attention of philosophers to the electric spectrum, Masson indicated the red hydrogen-line, hut without referring in an explicit way to its origin. Angstrom first separated the spectrum of gas from the spectra of metal. In the diagram he gave of the hydrogen-spectrum, he represented, by means of curves, the intensity of light along the whole length of the spectrum, especially the maxima of intensity within the red, the green, and the violet. These maxima corre- spond to Ha, H/3, H y, here expanded into bands, the breadth of which, as well as their decreasing intensity towards both ends, are indicated by the extension and steepness of the curves. After one of us published his first researches on the spectra of ignited gases, M. van der Willigen, in operating with strong induced currents, determined in a similar way the maxima of intensity of the hydrogen-spectrum. The spectra thus obtained are not calculated to prove the connexion existing between the bright lines of ignited gases or vapours and Fraunhofer's dark lines of the solar spectrum. Starting, in his first communica- tion made to the Eoyal Swedish Academy, 1853, from the theoretical conception “ that the dark lines of the solar spectrum are to be regarded as an inversion of the bright lines of the electric spectrum,” M. Angstrom concluded the coincidence of Ha with Eraunhoeer’s line C ; but the diagram shows that this conclusion was not based on exact measurement. One of us, in his publication of 1859, not being guided by any theoretical view on this point, first announced the coincidence of H/3 with Fraunhofer's E, and fixed the position of Hy near G, of Ha at a distance of two minutes from C. When at a later period he made use of Steinheil’s large spectral apparatus, he pointed out at first sight the exact coincidence of Ha with C, Hy with a marked black line at some distance from G, towards E. In operating with spectral tubes, M. Angstrom confirmed these results. (The spectroscope employed in 1859 being a small and imperfect one, there was given to the slit an aperture of more than three minutes. The adjustment was made with regard to H/3. Hence the error finally made in determining the position of Ha may be fully explained, by the circumstance that the illuminated border of the slit was observed instead of the illuminated aperture itself.) — Angstrom : “ Optische Hnter- , suchungen,” Poggendorfe’s c Annalen,’ vol. xciv. ; “ Ueber die ERAUNHOEER’schen Linien im Sonnenspectrum,” Ibid. vol. cxvii. Yan der Willigen : “ Over het electrische Spectrum, Yerhandelingen der K. Hollandsehe Academie (Natuurkunde vii. & viii.). Plucxer, Poggendorfe’s ‘ Annalen,’ vol. evii. p. 544. SPECTRA OF IGNITED GASES AND VAPOURS. 23 61. On sending the direct discharge of Ruhmkorff’s coil through a tube of glass from one-fourth to one-eighth of an inch in diameter, provided with electrodes of platinum or of aluminium, enclosing hydrogen at a tension of 5 to 10 millims., a luminous thread of light of a bluish-white colour was seen passing along the axis of the tube, without touching the glass. When analyzed by the prism, it gave a faint spectrum of the above-mentioned numerous bright lines, especially within the red and the yellow. Among these lines neither Ha nor Hy were seen ; H/3 only appeared, but less bright than many of the other lines. By interposing the Leyden jar and gradually increasing its charge (12), all lines became brighter, H/3 surpassing all other lines in brilliancy ; Ha appeared beautifully, Hy fainter. Hence we conclude that the numerous bright lines belong neither to the vaporized metal of the electrodes, nor to the decomposed interior surface of the glass, but solely to the hydrogen, constituting a new spectrum of it. This spectrum may be seen simultaneously with the three characteristic lines Ha, H/3, Hy ; but at an increased temperature, when these lines begin to expand, it entirely disappears. 62. We got only one spectrum of oxygen in operating exactly in the same way as we did in the case of nitrogen, with merely this difference, that under the same con- ditions a spectrum of equal brightness was obtained only by means of a stronger discharge. Accordingly if oxygen, enclosed in the spectral tube, be replaced by com- mon air, the spectrum of the oxygen it contains does not appear until after interposing the Leyden jar. We do not enter here into the detail of the oxygen-spectrum, but conclude with a general remark. Nearly all luminous lines of the spectra of the second order expand when the temperature of the ignited gas increases beyond a certain limit ; but neither do all lines reach the same brightness before expanding, nor do the lines in the different parts of the spectrum expand at the same temperature. That is seen best in the spec- trum of the second order of oxygen. The bright lines constituting the characteristic groups of its middle part oppose the greatest resistance to expansion. If they are best defined, the luminous lines towards the red extremity, most distinct at a lower tem- perature, are already expanded, while towards the violet extremity the luminous lines are scarcely developed ; they will be brightly developed, become well defined, and extend very far, after the ignited oxygen reaches a temperature at which the groups of the middle part are expanded. Hence arises the difficulty of representing the oxygen- spectrum. A drawing exhibiting the well-defined lines successively developed in its different parts is rather an ideal image than a true representation of nature. 63. Water introduced into a small spectral tube was kept boiling till the last traces of air were expelled, and then, before all the water was evaporated, the tube was hermetically sealed. The direct discharge, if passing, scarcely rendered the tube luminous, but with the intercalated jar the peculiar red light of hydrogen appeared, exhibiting the charac- istic lines Ha, H/3, Hy well defined. When these lines became gradually expanded, the lines of the oxygen-spectrum successively appeared with an increasing intensity, 24 DES. J. PLUCKEE AND J. W. IIITTOEF ON THE finally rising from the hydrogen-spectrum transformed into a continuous one. Here the heat of the discharge is increased by the increased density of the vapour of water, and reciprocally the evaporation is accelerated by the rising temperature of the discharge. The vapour of water is decomposed by the discharge ; the ignited hydrogen resulting from the decomposition exhibits a spectrum at a lower temperature than the resulting oxygen does. After the discharge ceases, oxygen and hydrogen are recomposed again to water. 64. Phosphorus , when treated like sulphur (35), exhibits a beautiful spectrum of the second order. Whatever may be the gradual change of the intensity of light produced by regulating as well the discharge as (by means of a lamp) the heat of the spectral tube, we get only one spectrum of bright lines successively developed. Among them there is one announcing at first sight the presence of vapour of phosphorus, a triple orange line, formed by two single lines of first intensity, and a third less bright one bisecting the interval between them. The other brightest lines are seen within the green. We get no difference at all by introducing into the spectral tube either common or red phosphorus. After the current had passed for some time, common phosphorus was seen, within the tube, transformed into a subtle powder of the red kind. 65. Chlorine , Bromine , and Iodine were among the substances first submitted to spec- tral analysis by one of us. On resuming the subject we fully confirmed the formerly obtained results, that not any two of the numerous spectral lines, characterizing the three substances, were coincident. By means of the electric current we got in all instances only spectra of the second order. We were especially desirous of ascertaining whether there existed a spectrum of iodine, corresponding to a lower temperature, the inverse or negative image of which agreed with the spectrum produced by absorption on sending sunlight (which, in order to prevent the influence of Fraunhofer’s dark lines, may be replaced by the light of phosphorus in combustion) through a stratum of heated vapour of iodine. Thus, indeed, we obtain more than fifty shaded bands, the breadth of which decreases from the violet to the red, constituting a spectrum of the first order. The flame of hydrogen in open air was not fitted to ignite vapour of iodine introduced into it sufficiently. But by feeding the flame by oxygen we got a new spectrum. Large fields, shaded by dark transversal lines, differently bounded, but quite similar to the third type of the spectra of vapour of carbon, constituted a spectrum of the first order. But the spectrum we might have expected according to theory was not seen. 66. Arsenic , when treated like sulphur and phosphorus, gives a well-defined spectrum of the second order. 67. So does mercury when introduced into a spectral tube from which air is expelled, either by means of Geissler’s exhauster, or by boiling the mercury within it. After a slight heating of the tube by means of an alcohol-lamp the discharge passes; and having once passed, it continues to do so, even without the lamp. Vapour of mercury SPECTRA OF IGNITED OASES AND VAPOURS. 25 opposing a comparatively small resistance to the passing current, we found it useful to intercalate at the same time a Leyden jar and a stratum of air. Thus, indeed, by regu- lating as well the density of the vapour as the thickness of the stratum, we obtained the best-developed spectrum. The least quantity of mercury, if vaporized, becomes visible by the passing current. Especially when mixed with other metals like arsenic, antimony, &c., we may detect even the least traces of it, which would entirely elude chemical analysis. Thus, for instance, we observed that arsenic, whatever may be its origin, is not free from mercury. After introducing a small quantity of it, which we heated by an alcohol-lamp when we placed it before the slit of the spectral apparatus, in a few moments four lines of great brightness, among which was a double yellow one, rose from a dark ground, but before the spectrum was fully developed it was abruptly replaced by another quite as brilliant. The first spectrum obtained belongs to vapour of mercury, first developed by evapora- tion, the second to arsenic, which increasingly vaporized at a higher temperature dis- putes the conduction of the discharge with the mercury, the vapour of which, according to its small existing quantity, reaches only a very low limit. The spectrum of arsenic remaining alone, gradually increased in brilliancy by the development and expansion of its bright lines. In cooling the spectral tube, by taking off the lamp, the spectrum of arsenic lost its extreme brilliancy; well-defined bright lines, the number of which gradually diminished, rose from a dark ground, and were replaced again by the spectral lines of mercury, till finally all light was extinguished. 68. The metals of alkalies, sodium, potassium, lithium, thallium show, even at the lower temperature of Bunsen’s lamp, a spectrum of the second order, consisting of bright lines, the number of which is increased by the higher temperature of the current, while the principal ones are expanded. 69. Barium, strontium, calcium show, even in Bunsen’s lamp, shaded bands, and a bright chief single line at the same time. This line, green in the case of barium, bluish violet in the case of strontium, violet in the case of calcium, fully exhibits the character of the bright lines in the spectra of the second order. The bands, if well developed, constitute a spectrum of the first order. We examined especially the spectrum of barium, by introducing its chloride into the hydrogen-flame. In making use of two prisms and employing a magnifying power of eighteen, we distinctly obtained the shading of the bands resolved into dark lines, finer and closer to one another than in former similar cases. Thus we proved that the band-spectrum of baryta is in every respect a spectrum of the first order. 70. Spectra of the first order were observed in the case of a few heavy metals only. Among these metals we mention in the first instance lead. We obtain its spectrum in Bunsen’s lamp, but in order to get it beautifully developed we must make use of the oxyhydrogen flame. The spectra we obtained were identically the same whatever com- pound of lead was introduced into that flame. We especially examined its combinations with chlorine, bromine, iodine, and oxygen. In all cases we observed larger bands, MDCCCLXV. e 26 DRS. J. PLUCKER AND J. W. HITTORF ON THE which by increased temperature were divided into smaller ones. Each band has a chan- neled appearance produced by fine dark lines, the darkness of which increases from the more to the less refracted extremity of the band, contrary to what takes place in the violet channeled spaces of nitrogen. Chloride of lead, when examined within our spectral tubes, showed no traces of bands ; they were replaced by bright lines. But on account of the great difficulty of vaporizing it, the spectrum of the second order, owing to lead, is best developed by the discharge of Ruhmkorff’s coil between two electrodes made from this metal and surrounded by an atmosphere of hydrogen. The spectrum of this gas being under these conditions nearly a continuous one (59), the bright lines of the lead-spectrum of the second order rise from a coloured ground. More than fifty lines were counted, although the fainter ones did not appear. 71. When either chloride or bromide or iodide of copper is introduced into the flame of Bunsen’s lamp, we get spectra of bands, but these bands are not exactly the same, they differ from one another by additional bands*. In the oxyhydrogen flame the bands are better developed, but we did not succeed in resolving the shadows of the hands into dark lines. At the same time four lines of single refrangibility appeared. The number of these lines was increased and the number of bands reduced, when chlo- ride of copper was examined within our spectral tubes. The well-known spectrum of the second order was fully developed, and every trace of bands extinguished, by dis- charging Ruhmkorff’s coil between two copper electrodes. 72. Finally, manganese exhibited a curious spectrum of the first order, most similar to that of carbon (third and fourth type (56)). The whole spectrum is equally divided into large fields, but these fields are shaded differently by fine transversal lines, the shadow increasing from the more to the less refracted extremity of each field. From the brighter less refracted part rise groups of bright lines, similar to the groups of carbon, but the lines of the groups are differently distributed. When Ruhmkorff’s large coil was discharged between two electrodes made from man- ganese (we surrounded them with an atmosphere of hydrogen), a pure spectrum of the second order, free from any traces whatever of the former spectrum, was obtained. Explanation of the Plates. In determining the different spectra both of the first and the second order, the dispersing prisms occupied invariably the same position, corresponding to the minimum deviation of the green hydrogen-line H/3, i. e. of Fraunhofer’s F. All spectra repre- sented in the Plates are referred to the three hydrogen-lines Ha, H/3, Hy, and the double sodium-line Na. Generally two prisms of about 60° and 45° were employed, * This fact has been noticed by At. A. Mitscheblich with regard to the chloride and the iodide, and attri- buted by him to the undecomposed salt (Toggendobff’s ‘ Annalen,’ 1862, vol. ii. p. 299). SPECTBA OF IGNITED GASES AND VAPOURS. 27 giving the distances of Ha and Na on one side and of Hy on the other side from H/3, by the following numbers of divisions of an arbitrary scale : 139-6, 100-5-101, 88-5. In the first Plate portions of all the coloured spectra are represented as they appear by making use of two additional prisms of 45°. PLATE I. contains spectra of the first order. The first spectrum, N, belonging to nitrogen, is taken under such conditions that both its extremities appear equally developed. To the whole spectrum is added a representation of two bands, C, of its more refracted part, obtained by means of the four prisms. Here a determined number of subtle dark transverse lines produce the channeled appearance. Likewise the configuration of two orange bands, A, and two green ones, B, is represented, exhibiting the character of the less refracted part of the spectrum (15-19, 27, 28). S represents the spectrum of sulphur, as obtained by means of an exhausted bent spectral tube enclosing sulphur moderately heated by an alcohol lamp, and traversed by the charge without an interposed jar (35, 36). Two green and two blue shaded bands, as seen by means of the four prisms, are repre- sented by A and B. C I shows the spectrum of vapour of carbon obtained by the combustion of cyanogen in oxygen. It exhibits within the large shaded fields groups of peculiar bright lines, the brilliancy of which it was impossible to represent. These groups are denoted by a , b , c , d, e, f\ g , h. The red extremity becomes fainter when the heat of com- bustion increases, and even appears more distinct if the combustion takes place in air (41-46). The configuration of One of the red bands, as seen when the four prisms are employed, is represented by A. C ii exhibits the spectrum of vapour of carbon obtained by means of spectral tubes enclosing oxide of carbon, the gas being decomposed by the electric discharge (49, 50). On taking away all characteristic groups, the remaining part of the spectrum, consisting only of three large shaded fields, is that obtained if the density of the gas be greater and the discharge too strong (51), as well as in the case of imperceptible traces of decomposed carbonic combinations (8). C hi shows the less refracted part of the brightest of the large shaded fields (51). C iv exhibits a peculiar distribution of light and shade within the violet, scarcely indi- cated in Ci, but well developed when olefiant gas instead of cyanogen is burnt in oxygen (48). 28 DBS. J. PLTTCKER AND J. W. HITTOEF ON THE PLATES II. & III. represent spectra of the second order, on a scale one-third larger than the scale of Plate I. In Plate II. N shows the second spectrum of nitrogen (20-23), O the spectrum of oxygen (63), S the second spectrum of sulphur (37, 38), Se of selenium (39). In Plate III. I shows the spectrum of iodine, Br of bromine, Cl of chlorine. Some remarks may be added here with regard to the conditions under which the spectra are obtained. Iodine was introduced into a bent spectral tube, and the tube exhausted as far as possible. While more recently tubes have been constructed which do not allow the discharge of Ruhmkokff’s large coil to pass, not even at a very short distance of the electrodes, the same effect will scarcely be obtained if iodine is enclosed in the tube. Accordingly the very first moment the phenomena described in art. 8 take place ; but soon after, vapour of iodine is developed, and by the heating power of the discharge we get, without the Leyden jar, a spectrum of mere iodine, consisting of very well-defined lines on a dark ground. After the interposition of the jar these lines became more brilliant, but remained well defined, and their number increased. Then the position and the intensity of the lines of the middle part were determined, while the red extremity was not at all developed, and the violet one most imperfectly. If the density of the vapour is increased by heating the tube by means of an alcohol lamp, the lines deter- mined are expanded, while the’ground becomes illuminated. The brilliancy so increases that the eye can scarcely bear it, till at last the discharge ceases to pass. While the middle part approaches to continuity, a certain number of delicate brilliant red lines, seen in the diagram, appear, and do not lose their distinctness as long as the discharge passes. Towards the violet extremity new lines likewise appear, hut though that extre- mity becomes most brilliant, we were not able to get the lines well defined. Accordingly the position of the expanded lines is approximately indicated by dotted lines. A drop of bromine was introduced into a small exhausted spectral tube. The tension of its vapour being too great to allow the discharge to pass, the vaporized fluid was expelled till the remaining vapour obtained a tension of about 6 centimetres. But by and by the vapour of bromine, combined with the platinum of the electrodes, was deposited on the interior surface of the tube, and after some time, evidently from want of sufficient conducting matter, the beautiful spectrum fainted almost suddenly. The spectrum was taken with the interposed jar. In this case Ha and H/3 are simulta- neously seen, but expanded, indicating traces of remaining water. The lines of oxygen are not seen. Without the jar hydrogen is not indicated. Then four bright lines, belonging to bromine, appear in the neighbourhood of Ha. While, with the interposed jar, they are fully expanded like this hydrogen-line, a less refracted subtle line appears, always remaining most distinct. The blue and violet extremity of the spectrum is better defined than in the case of iodine. SPECTRA OF IGNITED GASES AND VAPOURS. 29 The spectrum of chlorine is taken under similar conditions with the spectrum of bromine. The spectral tube most carefully exhausted was several times filled with chlorine and exhausted again. The final tension of the remaining gas was about 6 centi- metres, as it was in the former case. P exhibits the spectrum of phosphorus (64). We conclude with a general remark regarding more or less all the spectra of the second order represented in Plates I. & IT. The intensity attributed to the different bright lines constituting these spectra corresponds to the condition in which they are best developed.. There seems to be a general rule that all luminous lines become brighter and are finally expanded, when the heating-power of the discharge continually increases. But for different lines the intensity does not rise in the same ratio : thus lines less brilliant at first than others may afterwards surpass them in brilliancy. The inten- sity attained by the different luminous lines before they are expanded greatly differs ; lines may disappear by expansion, while others of the same spectrum do not yet appear. The least-refracted lines generally resist expansion the most. MDCCCLXV. F S pect Nitrogen HH iiiiSili ! & m&W; ■ msmH •t:k| Spectra secundi Ordinis Ni trojciii^/ Ncl jj t Phil. Trans. MDCCCLXYTlateH. >ni Oxygen ii Sulphuris Selenii i. j ih_— iL ! i 3. Si Engraved and print edT>y A..Henrv. Bonn. Spectra secundi ordinis ,c J B C 1 1 1 Phil. Trans. MDCCCLXV.PlatellL i Bromi Chlori Phosphori in r — I — i — L_i J. 1. 1 I I I I Ensnared anl^rinte.l"by A.Eenrj Bonn. [ 31 ] II. On the Osteology of the genus Glyptodon.. By Thomas EL Huxley, F.B.S. Received December 30, 1863, — Read January 28, 1864, Part I. — -The history of the discovery and determination of the remains of the Eoplophoridce. Part II. — -A description of the skeleton of Glyptoclon davipes, Owen ( Hoplophorus Selloi, Lund?). § 1. Description of the Skull. § 2. Description of the Vertebral Column. Part I. — The history of the discovery and determination of the remains of the Hoplo- phoridae, or animals allied to. or identical with , Glyptodon clavipes. The earliest notice of the discovery of the remains of Glyptodon-Yike animals is con- tained in the following extract from a letter, addressed to M. Auguste St. Hilaire by Don Damasio Laranaga, Cure of Monte Video, which appears in a note at p. 191 of the fifth volume of the first edition of Cuvier’s ‘ Ossemens Fossiles,’ published in 1823: — “I do not write to you about my Dasypus (Megatherium, Cuv.), because I propose to make it the subject of a memoir which, I trust, may not be unworthy of the 'atten- tion of those European savants who take an interest in fossils. I will merely say that I have obtained a femur, which was found in the Rio del Sauce, a branch of the Saulis Grande. It weighs about seven pounds, and may be six or eight inches wide. In all points it resembles the femur of an Armadillo. I will send you one of its scales. The tail, as you have seen, is very short and very large ; it also possesses scutes, but they are not arranged in rings, or in whorls. These fossils are met with, almost at the sur- face, in alluvial, or diluvial, formations of a very recent date. It would seem that similar remains exist in analogous strata near Lake Merrim, on the frontier of the Portuguese colonies.” Cuvier expresses no opinion as to the accuracy, or otherwise, of Don Damasio Laranaga’s identification of his Dasypus with the Megatherium, an identification which, it will be seen, was erroneous. The volume of the Transactions of the Royal Academy of Sciences of Berlin for the year 1827 contains a memoir by Professor Weiss* upon the collections of fossils and minerals gathered in South America by Sellow, accompanied by five plates, four of which display excellent representations of various portions of the dorsal and caudal dermal armour, and of part of a femur, of one or more species of Glyptodon. Some of these fossils (the fragments of the dorsal dermal armour) were obtained at three feet from the surface, in the marly clay of which the banks of the Arapey Chico (a branch * Ueber das siidliche Ende des Gebirgzuges von Brasilien in der Provinz San Pedro do Sul und der Banda Oriental oder dem Staate von Monte Video : nach den Sammlungen des Herrn Fa. Sellow, von Herrn Weiss (Gelesen in der Akademie der Wissenschaften am 9. August 1827, und 5. Juni 1828). MDCCCLXV. G 32 PROFESSOR HUXLEY ON THE OSTEOLOGY OE THE GENUS GLYPTODON. of the Arapey Grande, an affluent of the Uruguay) are formed. The skeleton of the Megatherium now at Madrid was found in a similar clay which underlies Buenos Ayres. The femur and the fragment of caudal armour were procured from the banks of the Quegnay, a more northern affluent of the Uruguay than the Arapey. Weiss remarks upon these fossils ( l . c. p. 276) “that it can hardly he doubted that they belonged to no other animal than the Megatherium , Cuv. Cuvier himself pub- lished, in a note to p. 191 of his ‘ Recherches sur les Ossemens Fossiles,’ t. v. le partie, the first information which he received, in 1823, that his Megatherium was a loricated animal. M. Laranaga, parish priest of Monte Video* (from whom this information was derived, and in whose house M. Sellow, in 1822, saw two fragments of the armour, one belonging to the back and the other to the tail, which were found between Monte Video and Maldonado, in a gully opening into the Arroyo de Solis), believed the animal to be an Armadillo, Dasypus ; Cuvier had already pointed out the similarity of the extremities to this genus and to Myrmecopliaga. However, the armour plates found on the Arapey show no trace of a zonary arrangement, and the fragments possessed by M. L Aran ag a also leaving a doubt on this point, it may remain an open question whether the Megatherium possessed a veritably jointed armour, or whether it was not more probably provided with a solid shield.” The figures show, and Professor Weiss remarks upon, the raised conical form of the marginal pieces of the carapace. In the course of his description of the parts of the skeleton of a Megatherium sent to this country by Sir Woodbine Parish, Mr. Clift f remarks, “ In these latter instances the osseous remains were accompanied by an immense shell or case, portions of which were brought to this country ; but most of the bones associated with the shell crumbled to pieces after exposure to the air, and the broken portions preserved have not been sufficiently made out to be, at present, satisfactorily described. Representations, how- ever, of parts of the shell in question are given in the plate annexed.” The plate (46) to which reference is here made exhibits views of the inner and outer surfaces of parts of the carapace of a Glyptodon. In a note (p. 437) Mr. Clift mentions that casts of the principal bones in question have been sent, among other places, to the Jardin des Plantes at Paris. The next work upon this subject in the order of time, is the very valuable essay com- municated by Professor E. D’Alton to the Berlin Academy in 1833 Sellow had * [“ A friend of natural history and, in every way, an estimable man, who has now unfortunately become blind,” writes M. Sellow regarding him to M. von Olfers on the 10th October 1829. We can therefore no longer look for the appearance of his promised essay on these fossil remains.] t “ Some account of the Remains of the Megatherium sent to England from Buenos Ayres by Woobblne Parish, jun., Esq., F.G.S., E.R.S.” By William Clift, Esq., E.G.S., F.R.S. Bead June 13, 1832. Transactions of the Geological Society, vol. iii. 2nd series. t “ Ueber die von dem verstorbenen Herrn Sellow aus der Banda Oriental mitgebrachten fossilen Panzer- Eragmente und die dazu gehorigen Knochen-Ueberreste,” with four plates. The volume of the * Abhand- lungen der Koniglichen Akademie der Wissenschaften,’ in which this essay appears, was published in 1835. PROFESSOR HUXLEY OH THE OSTEOLOGY OF THE GENUS GLYPTODON. 33 been compelled by the local authorities to send to Bio Janeiro all the bones and the finest pieces of the carapace, which he discovered in association with the fragments of dermal armour figured by Weiss*; but, by good fortune, these additional materials at length found their way into the Berlin Museum, and afforded D’ Alton the materials for his memoir, in the first section of which the pieces of the carapace of the fossil animal are described ; while the second section is devoted to an account of the structure of the dermal armour of living Armadillos, and the third to a description of the fossil bones found in juxtaposition with that dermal armour. The results of the comparison of the fossil armour with that of existing Armadillos are thus stated : — “ If we compare these fossil dermal plates with those of living species of Dasypus , it becomes obvious that all the peculiarities of the former may be paralleled by the latter; but with this difference, that while, as appears from Sellow’s report, all the fossil plates belonged to one and the same animal, their peculiarities are not all found associated together in any one living species. The majority of the fossil plates which were distant from the margin, e.g. those represented by Weiss in figs. 1, 4, & 5, and many described above, exhibit the greatest similarity to the dermal plates of Dasypus niger ; and thence it may be concluded that the epidermis of the Dasypus of the ancient world (if for brevity’s sake I may so name the animal), like that of the Dasypus niger , was divided differently from the bony plates, and that strong hairs were arranged in the interstices of the epidermic scales. “ The pieces which belonged to the edge, or the pointed marginal scutes (Zacken), most nearly resemble those of D. Poyou (fig. 12 of our first Plate), and D. grandis shows a somewhat similar formation. In addition, the thoracic shield and the moveable zones of D. villosus (fig. 18) are also provided with pointed marginal scutes; and, according to Azara, the Tatou pichey exhibits similar structures. But in all the animals provided with such pointed scutes, they are directed from above, and forwards, downwards, and * Professor Owen writes (On the Olyptoclon clavipes, Geol. Trans, vol. hi. pp. 82, 83), “ The portions of the tessellated bony armour figured by Professor Weiss, pi. 1 and 2, and described at p. 277 of his memoir, were obtained by Sellow' on the Arapey-Chico in the province of Monte Yideo ; but no bones either of the Megatherium, or any other animal, are mentioned as having been associated with them. A third series of fossils, in which fortunately some bones of the extremities were discovered associated with the tessellated bony case,, was presented to Sellow by the President of the province of San Pedro, with the information that they had been originally discovered in the proximity of Rio Janeiro.” ■ This, however, appears to be a misapprehension of the state of the case.. The armour figured by Weiss in pi. 1 and 2 of his memoir, and the “ third series of fossils ” were associated together : and so far from the President of the province of San Pedro having presented anything to Sellow, it was Sellow who was obliged to present the fossils to the President, or at any rate, to dispose of them according to his orders. “ Denn die Aufforderung. des damaligen Prasidenten der Provinz San Pedro, des Yisconde des S. Leopoldo, nothigte ihn [Sellow] den hauptsachlichsten Theil dieser fossilen Ueberreste nach Rio Janeiro abzuliefern.” It is therefore sufficiently obvious that the fossils were not found at Rio Janeiro, but were sent to that place from Arapey-Chico. G 2 34 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. backwards ; and therefore some of the fragments may be referred to the left, and some to the right side From the preceding comparisons it follows that the fossil scutes are similar to those of the thoracic and pelvic shields of different living Armadillos, although they differ from them in many respects. But if objections should still be raised to regard- ing the animal which bore the fossil armour as an Armadillo (Giirtelthier), two replies may be made. In the first place, neither the entire skeleton nor the perfect shell of the animal have been obtained. Of the skeleton, the vertebral column, the ribs, and sternum are wanting — or exactly those parts which the moveable zones (Gurtel) would have covered. Secondly, the moveable zones themselves, although among the charac- teristic features of the Armadillos, are of less importance than was formerly believed, as Azara has already pointed out.” The state of the bones indicated that they appertained to a young animal, the epi- physes being distinct. Those described belonging to the fore limb are, a part of the scapula (?), the distal end of the left humerus, the radius and ulna, nearly perfect, and eighteen bones of the fore foot. Of the latter, five belonged to the carpus, of which the three proximal are interpreted by D’Alton as the semilunare (Mondbein), cuneiforme (das dreieckige Bein), and pisi forme (Erbsenbein). I shall endeavour to show, in the course of my description of the specimen which forms the subject of this memoir, that the determinations of the semilunare and cuneiforme are perfectly correct, but that the so-called pisiforme is not rightly named. The distal bones are, according to D’Alton’s interpretation, which I can fully confirm, the magnum and the unciforme. Two entire metacarpal bones, and fragments of another, are considered by the author of the memoir to correspond with the third, fourth, and fifth of an ordinary five-toed fore foot ; but they are really the second, third, and fourth, Professor D’Alton having taken the surface of the cuneiform, which articulates with the fifth metacarpal, for the surface of articulation with the pisiform. The phalanges of the digits belonging to these metacarpal bones, and three of their sesamoid bones, are carefully described and figured. The resemblances of the bones of the forearm with those of the existing Armadillos are pointed out, especial weight being laid upon the extension of the cuneiform round the unciform, and its articulation with what D’Alton supposes to be the fifth meta- carpal ; and certain analogies of the fore foot with that of the mole are indicated. A fragment of the distal end of a leg-bone, the seven tarsal bones, the four outer metatarsal bones ; their digits, except the ungual phalanges ; and some other bones of the hind foot, in a more or less fragmentary state, are described and figured, and atten- tion is drawn to the remarkably short and strong character of the foot. In conclusion B’Alton remarks, “Though, as I have endeavoured to show above, there is a certain agreement between the manus of the fossil animal and that of the Armadillos, yet the foot shows us no greater similarity than may be observed between it and many other five-toed animals. Hence the osteology of the primeval animal does not afford a sufficient confirmation of the view which we derived from the consideration of the carapace, viz. that the bones, together with the fragments of dermal armour. PKOEESSOK HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 35 might have belonged to an animal nearly allied to the Armadillos, or perhaps even to a very large, probably extinct, species of Dasypus. The fossil bones are too few to afford a safe foundation for so decided an opinion respecting the zoological affinities of the animal. A tolerably perfect skeleton is necessary in order to enable us, from the bones alone, to draw a safe conclusion as to the structure pf the remainder of an animal.” Singularly enough, D’ Alton does not mention the Megatherium throughout this paper, which however affords, by implication, an ample demonstration that the bony armour described has nothing to do with that animal*. In 1836, Laurillard, in editing the eighth volume of the second edition of Cuvier’s ‘ Ossemens Fossiles,’ appends the following note to the letter of Don D. Laranaga, quoted above : — “ It is very possible that the Megatherium was, in fact, covered by a scaly cuirass ; but the great fragments which have been found must not be hastily attributed to it ; for the plaster casts sent from London f prove that an Armadillo of gigantic size coexists with the Megatherium on the plains of Buenos Ayres. These characteristic fragments consist of a calcaneum, an astragalus, and a scaphoid, which depart from those of existing Armadillos only in size, and by purely specific differences.” In 1836, then, it was clearly made out that the cuirassed extinct animal of South America is not the Megatherium and is allied to the Armadillos. However, Dr. Buckland, whose Bridgewater Treatise appeared in this year, and who therefore could hardly have been acquainted with the views of D’Alton and of Laurillard, still associated the dermal armour with the Megatherium — supporting his views by an elaborate and inge- nious teleological argument, which, like most reasonings of the kind, appeared highly satisfactory. But, in 1837, all further doubt upon the subject was removed by the dis- coveries of Dr. Lund, who, in that year, despatched to Copenhagen the second of the remarkable series of memoirs in which he reconstructed the ancient Fauna of Brazil J. In this paper Dr. Lund established the genus Hoplopliorus upon the dermal armour and certain bones of an edentate quadruped closely allied to, if not identical with, the “ Dasypus ” of Laranaga. Hoplophorus euphractus , the sole species of the new genus described in the memoir, was estimated by its discoverer to be of the size of an ox, and to have been provided with a carapace most nearly resembling that of Tolypeutes, but of an astonishing thick- ness. The extremities are said to have the general structure of those of the Armadillos, * Thus Muller says in his memoir on the hind foot, cited below, “ In der letzten Abhandlung ist von Herrn D’ Alton bewiesen, dass der Panzer nicht dem Megatherium angehort.” t Vide swpra, p. 32. Mr. Pentland appears to have been led to the same opinion by the examination of these casts in 1835. See Transactions of the Geological Society, vol. vi. ser. 2nd, p. 85, and Mr. Pentlaxd’s letter to M. Aeago in the ‘ Comptes Rendus’ for March 11, 1839. £ “ Blik paa Brasiliens Dyreverden for sidste Jordomvaeltning. Anden Afhandling : Patte dyrene. Lagoa Santa, 16de Novbr. 1837,” published in ‘ Det Kongelige DanskeYidenskabernes Selskabs Naturvidenskabelige og Mathematiske Afhandlingar,’ Ottende Deel, 1841, p. 70. A notice of Lund’s labours, containing the names of his genera, is to be found in the ‘Oversigt over det Kongelige Danske Yidenskabernes Selskabs Fordhandlingar i Aaret 1838/ published by Oksted, the Secretary of the Academy. 36 PROFESSOR HUXLEY ON THE OSTEOLOGY OE THE GENUS GLYPTODON. the feet being short and thick, with remarkably broad and short nails ; so that they must have resembled those of an Elephant, or a Hippopotamus. The skull was sloth-like, and its jugal arch exhibited the structure characteristic of those animals. The teeth were similar to the molars of Ccvpybara, but simple instead of being made up of many plates. Professor Bronn, publishing the .second edition of his 4 Lethsea Geognostica ’ in the spring of 1838, and unacquainted with Lund’s labours, proposed the name of Chlamy- dotherium for the animal to which the carapace described by Weiss and D’Alton belonged, in case the foot should really appertain to it ; and Orycterotherium , in case the foot should belong to a different animal. In March of the same year, it appears that M. Vilardebo, Director of the Museum of Monte Video, and M. Isabelle published conjointly, in Nos. 2551, 2553, and 2555 of a journal, the ‘ Universal,’ an account of an animal which they had discovered on the Pedernal, in the Department of Canelones*. After removing a thin layer of clay, these observers met with a shield formed of pieces of bone separated from one another by a slight interval ; these pieces, 25 to 50 millimetres in diameter, and varying in thickness from 12 to 40 millimetres, were hexagonal: the largest occupied the dorsal region of the carapace, and the smallest its lateral regions. Each polygon presented a central disk (14 to 27 millimetres in diameter), from whence radiated six or eight lines, between which as many quadrangular arese were left. These pieces of bone were symphysially united so as to form a very regular mosaic : the cara- pace appeared to be fringed with conical pieces forming a semicircle of 24 centimetres. The carapace was about 4 metres wide, and was as convex as a cask. The bones dis- covered in it were lumbar vertebrae and pelvic bones. In another place was discovered a femur about 0-57 metre long, with many plates of the carapace, and a tail formed of a single mass of bone (covered nevertheless by pieces soldered together), in the middle of which were widely separated caudal vertebrae. The tail was more than 0-50 metre long, and more than O' 36 metre in diameter at the base. Tire authors discuss the question — to what class do these fossils belong 1 — with much sagacity, and conclude by expressing the opinion that they appertain to a species of Dasypus , which they term I), antiquus, and which they briefly characterize as follows : 44 Cingulis dorsalibus nullis: verticillis caudalibus nullis.” The volume of the Transactions of the Danish Academy, already cited, contains another communication from Dr. Lund, dated Lagoa Santa, September 12, 1838, in which he speaks of the fossils described by D’ Alton, and identifies the animal to which they belonged, generically, with Hoplophorus, though he regards it as a distinct species, and names it Hoplophorus Selloi. Accompanying this paper are sundry figures of parts of the carapace and of bones of the hind foot of Hoplophorus. Dr. Lund returns to the subject in a long letter addressed to M. V. Audouin, dated the 5th of November 1838 (extracts from which are published in the 4 Comptes Rendus ’ for the 15th of April 1839), which contains an enumeration, with brief descriptive notices, of the seventy-five species of fossil Mammalia which this untiring explorer had * See the Bulletin de la Societe Geologique de France, t. xi. p. 159 (1840). PROFESSOR HUXLEY ON THE OSTEOLOG-Y OF THE GENUS GLYPTODON. 37 extracted in the preceding five years from the caverns of Brazil. Among the rest the writer describes : — “ 6°. Hoplophorus , a genus very remarkable for the heavy proportions of its species, for their gigantic size, as well as for the singular manner in which it combines different types of organization ; however, their characters approximate them most nearly to the Sloth family. These strange animals were armed with a cuirass which covered all the upper part of the body, and which was composed of little hexagonal scutes, except in the middle of the body, where the scutes took a quadrate form, and were disposed in innumerable transverse bands. The bones of the trunk, as well as the great bones of the extremities, are also very similar to those of the Tatous, and particularly to those of the Cachicames ; but the bones which compose the feet are so shortened and have their articular faces so flattened, that nothing similar is to be seen in any animal skeleton, and that it is inconceivable how such feet should have been used in digging. The form of the teeth also indicates that these singular animals could feed only on vegetable sub- stances, and it is to be supposed that they grazed after the fashion of the great Pachy- derms. However this may be, the Hoplophorus , of which M. Lund describes two species, present the peculiarity, hitherto regarded as special to the Sloth, of having a descending branch to the zygomatic arch. These two species were as large as an ox. Fragments of the skeletons have already been described by MM. Weiss and D’Alton of Berlin.” — Loc. cit. pp. 572, 573. A summary of Lund’s researches, despatched by him from Lagoa Santa on November 5, 1838, and published in the Ann ales des Sciences Naturelles for 1839, under the title of “ Coup d’ceil sur les especes eteintes de mammiferes de Bresil : extrait de quelques memoires presentes a l’Academie Boyale des Sciences de Copenhague,” gives a sub- stantially similar account of Hoplophorus. The species Hoplophorus Selloi is identified with the cuirassed animal described and figured by Weiss and D’Alton. The sixth volume of the second series of the Transactions of the Geological Society contains an elaborate memoir by Professor Owen* on the bones associated with the dermal armour, figured by Mr. Clift in the memoir already cited ; and on certain teeth, upon which the genus Glyptodon was founded by the same writer, in Sir Woodbine Parish’s work on Buenos Ayres 'j*. Professor Owen considers these remains to be specifically identical with those collected by Sellow, and described by Weiss and D’Alton ; so that if Lund was right in ascribing the same fossils to his genus Hoplophorus, Glyptodon becomes a synonym of the latter. In the memoir under consideration the general form and the minute structure of the * “ Descriptions of a tooth and part of the skeleton of the Glyptodon clavipes, a large quadruped of the eden- tate order, to which belongs the tessellated bony armour described and figured by Mr. Clift in the former volume of the Transactions of the Geological Society, with a consideration of the question whether the Megatherium possessed an analogous dermal armour.” By Richard Owen, Esq., F.G.S., F.R.S. (Read March 23rd, 1839 : an abstract of this paper appeared in No. 62 of the ‘ Proceedings.’) f * Buenos Ayres and the provinces of the Rio de la Plata,’ 1838, p. 178 e. 38 PEOFESSOE HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. teeth, the distal end of the humerus, the radius, two phalanges of the fore foot, “ the anchylosed distal extremities of the tibia and fibula, an astragalus, calcaneum, seaphoides, cuboides, external cuneiform bone, the three phalanges of the second toe, and the mid- dle and distal phalanges of the third and fourth toes, with a few sesamoid bones,” all belonging to the left side, are described ; while the tooth and the bones of the leg and foot are figured. Professor Owen considers that the dental characters “ seem to indicate a transition from the Edentata to the pachydermatous Toxodon ,” and sums up his general conclu- sions as to the affinities of Glyptodon thus : — “ It may be concluded, therefore, that the extinct edentate animal to which belongs the fossil tessellated armour described by Weiss, Buckland, and Clift, cannot be called an Armadillo, without making use of an exaggerated expression, and still less a species of Megatherium ; but that it offers the type of a distinct genus, which was much more nearly allied to the Dasypodoid than to the Megatherioid families of Edentata, and most probably connected that order of quadrupeds with the heavy coated Rhinoceros of the Pachydermatous group” (l. c. p. 96). In the same year (1839) Professor D ’Alton proposed for the animal, the remains of which he had originally described, the name of Pacliypus ; so that by this time no fewer than six names had been applied to mammals all of which are certainly closely allied to the Hoplophorus of Lund, whether they are, or are not, generically identical with it, and which may therefore be appropriately termed Hoplophoridce. In 1845 Professor Owen returned to the Glyptodon question, in the ‘Descriptive and illustrated Catalogue of the Fossil Organic Remains of Mammalia, and Aves contained in the Museum of the Royal College of Surgeons of England.’ It is here stated (p. 107) that “those specimens of the present genus which were presented to the College by Sir Woodbine Parish are from a low marshy place, about five feet below the surface, in the bank of a rivulet, near the Rio Matanza, in the Partido of Canuelas, about twenty miles to the south of the city of Buenos Ayres.” The parts thus found associated are not stated, with the exception of the bones of the left hind leg and foot (p. Ill), to have belonged to the same individual. They consist of a molar tooth, part of the left ramus of the lower jaw, a fragment of the humerus, the left radius, a metacarpal bone and two phalanges, the shaft and distal epiphyses of the femur (1), the anchylosed distal ends of the tibia and fibula, and numerous bones of the left hind foot. These had already been described and figured in the Geological Society’s Transactions. As new specimens, there are described and figured an almost, entire carapace of Glyptodon clavipes, from the Pampas of Buenos Ayres, and many dermal bones, all of which are marked “ Purchased,” and appear not to have been accompanied by bones of the endoskeleton. Nos. 551, 552, 554, 555, 556, 557 are fragments of carapace, all presented by Sir W oodbine Parish, and obtained from the locality mentioned above. They are ascribed by Professor Owen to no less than three distinct species, however, PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 39 viz. Glyptodon clavipes, G. reticulatus, and G. ornatus ; a fourth species, G. tulerculatus, is based upon purchased specimens, from the Pampas of Buenos Ayres, the precise locality of which is not stated. The fact that the dermal ossicles of three species of Glyptodon were found in the same locality as the bones described, and the absence of any evidence demonstrating the association of the ossicles ascribed to G. clavipes, rather than those attributed to the other species, with the bones, throws, it will be observed, some doubt upon the certainty of that ascription, and opens the question whether the bones really belonged to one form of carapace or to another. Of the Plates which illustrate the c Catalogue,’ the first contains a side view, partly restored, of the Glyptodon clavipes ; the second, views of the carapace and tail ; the third, of the skull ; the fourth and fifth, of parts of the carapace ; and the description of the Plates comprises accounts of the structure of the skull and of the tail, parts which had not been received until after the printing of the body of the catalogue. In what locality the skull and the tail were obtained, and upon what evidence they are ascribed to the particular species, G. clavipes , is not stated. The lower jaw and the defensive bony covering of the skull in plate 1 “ are restored on the authority of an original sketch of an entire specimen of this species of Glyptodon transmitted to Sir Woodbine Parish from Buenos Ayres.” The bones of the fore foot are given in outline after D’Alton. On the 8th of June, 1846, the late Johannes Muller read a short paper to the Ber- lin Academy upon the bones of the leg and hind foot described by D’Alton, which had been worked out and mounted by the help of Professor Owen’s memoir. This paper, accompanied by an excellent plate, was published in 1849*. The number of the ‘ Comptes Bendus ’ for August 28, 1855, contains a “ Description d’un nouveau genre d’Edente fossile renfermant plusieurs especes voisines des Glypto- dons, et classification methodique de treize especes appartenant a ces deux genres,” by M. L. Nodot, Director of the Museum of Natural History at Dijon; and this essay, enlarged and illustrated with plates, appeared two years later in the 4 Memoires de l’Academie Imperiale de Dijon,’ Deuxieme Serie, tom. v. 1857f. M. Nodot, in his introductory remarks, states that Vice-Admiral Dupetit brought back from Monte Video, in 1846, a great number of fossil bones which had been collected by Dr. Numez on the banks of the river Lujan, and were given to the Vice-Admiral by the orders of the Dictator Rosas. Admiral Dupetit presented most of these remains to the Museum of the Jardin des Plantes in Paris ; but dying before * “ Bemerkungen fiber die Fussknoehen des fossilen Giirtelthiers ( Glyptodon clavipes, Ow.),” Abhand- lungen d. Konigl. Akad. d. Wissenschaften, 1849. t Under the title “ Description d’un nouveau genre d’Edente fossile renfermant plusieurs especes voisines du Glyptodon, suivie d’une nouvelle methode de classification applicable a toute l’histoire naturelle et speciale- ment a ces animaux. Avec un atlas de douze planches lithographiees.” MDCCCLXV. H 40 PROFESSOR HUXLEY ON THE OSTEOLOGY- OF THE GENUS GLYPTODON. he had disposed of all, his widow bestowed two boxes full of detached dermal ossicles on the Dijon Collection. Out of these, by dint of four months’ constant toil, M. Nodot reconstructed the carapace. Subsequent investigations in the store-rooms of the Jardin des Plantes revealed almost the whole of the tail, and many important parts of the skeleton, of what M. Nodot believed to be the same individual animal, mixed up, however, with fragments of Mylo- don, Megatherium , and Scelidotherium. Besides these, M. Nodot found the tolerably complete extremity of the tail of another individual of the same genus in the Geological Gallery, and the right half of a lower jaw with the teeth, which he judged to belong to this individual. The bones which M. Nodot, guided as it would seem chiefly by their colour, identi- fies as belonging to the same individual with the carapace, are, “ the lateral and poste- rior part of the cranium, the occiput, the meatus auditorius, the zygomatic arch and its long apophysis, three alveoli, and the sagittal crest ; the atlas, the axis, the vertebra of the fifth ring of the tail ; the two femora entire ; the tibiae and fibulae anchylosed ; the calcanea; the astragali ; the other tarsal bones ; the left metatarsus ; the three external toes of the left hind foot ; the left radius ; the ungual phalanx of one of the digits of the fore foot ; and the ungual phalanx of an internal toe of the hind foot.” The cara- pace and the tail are fully described by M. Nodot, who considers their peculiarities sufficient to justify him in establishing for these remains the new genus Schistopleuron. How far he was justified in so doing is a point which must be discussed at the end of this memoir ; but there can be no question that “ Schistopleuron ” is one of the IIoplo- phoridce, closely allied to Glyptodon clavipes ; and hence M. Nodot’s descriptions of the mandible, sternum, and femur constitute substantial additions to our knowledge of the organization of that family. The mandible is unlike the sketch furnished to Professor Owen and adopted by him, but very like that which will be described below. The first piece of the sternum and the first two ribs were so anchylosed together as to leave no trace of their primitive sepa- ration. On the 14th of November, 1862, 1 presented to this Society a “ Description of a new Specimen of Glyptodon, recently acquired by the Royal College of Surgeons of England,” which was published in the fifty-third Number of the ‘ Proceedings of the Royal Society.’ The remains of the specimen, described briefly in this preliminary notice and, in full, in the present memoir, were presented to the Royal College of Surgeons by Senor Don Maximo Terrero, having been discovered in 1860 on the estate of his brother, Senor Don Juan N. Terrero, which is situated on the banks of the river Salado, in the district of Monte, in the Province of Buenos Ayres, and about eighty miles due south of the city of that name. No portions of any other animal, nor any duplicate bones, have been discovered among the osseous relics the description of which has been entrusted to me by the authorities PEOEESSOE HUXLEY ON THE OSTEOLOG-Y OF THE GENUS GLYPTODON. 41 of the College of Surgeons — a circumstance which justifies the belief that they all belonged to one and the same animal, and gives them a peculiar value, the more especially as there can be little doubt of the specific identity of the new specimen with the animal to which the skull ascribed by Professor Owen to Glyptodon clavipes belongs. I have thus been enabled to add to what was already known of Glyptodon clavipes, descriptions of the most essential peculiarities of the fore part of the skull, the entire palate, the mandible, the greater part of the spinal column, the pelvis, and the com- plete fore and hind feet, and to announce the existence, in this animal, of a conforma- tion of the spinal column hitherto unknown in the Mammalian, and, indeed, in the Vertebrate series — the last cervical and two anterior dorsal vertebrae being anchylosed together into a single osseous mass articulated by ginglymi with the rest of the vertebral column. As another very remarkable peculiarity of this genus, I have pointed out the extraordinary characters of the pelvis, and the fact that the cuneiform bone in the carpus articulates with two metacarpal bones, the fourth and fifth, while the unciform does not articulate with the fifth at all. Since the appearance of my paper in the 6 Proceedings of the Royal Society,’ and in- deed not until the months of May and June 1863, M. Serres, apparently unacquainted with what had been done in these matters, has redescribed the joint between the second and third dorsal vertebrae, though he appears to be still unaware of the existence of the 4 trivertebral bone.’ In addition, M. Serres makes known the interesting circumstance, that the posterior edge of the manubrium of the sternum, anchylosed (as M. Nodot had pointed out, though M. Serres does not refer to him) with the first pair of ribs, pre- sents two concave articular facets, by which it was united with the rest of the sternum, which must have presented two convex surfaces adapted to the foregoing in order to allow of a movement of flexion. M. Serres is of opinion that this mechanism is intended to allow of the retraction of the head : “II est done vraisemblable qu’au moment du danger, peut-etre meme que dans le repos ou le sommeil, le Glyptodon flechissait le col pour ramener la tete sous la coupole de la carapace”*. In his second communication to the Academy, M. Serres still speaks of the “anchy- losis of the first two dorsal vertebrae ” onlyf . Professor Burmeister, Director of the Museum at Buenos Ayres, has been good enough to communicate to me a letter, addressed by him to the Editor of the 4 Nacion Arjentina’ on the 5th July, 1863, commenting upon a lecture upon the Glyptodon which I delivered before the President and Council of the Royal College of Surgeons, which was published in the Medical Times and Gazette for the 28th of February and * “Note sur deux articulations ginglymo'ides nouvelles existant chez le Glyptodon, la premiere entre la deuxieme et la troisieme vertebre dorsale, la seconde entre la premiere et la deuxieme piece du sternum. Par M. Sebkes” (Comptes Eendus, May 11, 1863). t “ Deuxieme Note sur le developpement de 1’ articulation vertebro-stemale du Glyptodon, et les mouvemens de flexion et d’ extension de la tete chez cet animal fossile. Par M. Sekbes” (Comptes Eendus, June 1, 1863). H 2 42 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 7th of March, 1863, and which contains the substance of the statements previously- published in the ‘Proceedings’ of this Society. Professor Bukmeister affirms that the skeleton of the Glyptodon in the Museum of Buenos Ayres is much more perfect than that in the lloyal College of Surgeons ; that it has the seven cervical vertebrae complete ; and that the five middle cervical vertebrae are anchylosed together, while the seventh is very delicate and fragile. Under these circumstances, it would appear that Professor Burmeister considers the trivertebral bone (my description of which he confirms) to be composed of the three anterior dorsal vertebrae. Professor Burmeister is further of opinion that the peculiar mechanism of the joint formed by the trivertebral bone with the rest of the spinal column has not that respi- ratory function which I have ascribed to it; but, with M. Serres, he thinks that its object is to allow of the application of the cephalic shield to the anterior aperture of the shield of the body. Professor Burmeister goes on to remark — “ As little do I agree with Mr. Huxley as to the immobility of the ribs, which are wholly wanting in the London skeleton. The skeleton of the Museum of Buenos Ayres has nine ribs, three of which being complete, prove that they possess a certain mobility, moving downwards and backwards on their articulations with the spinal column, as in other Mammalia, but without doubt in a manner somewhat different from the ordinary way.” I am at a loss to divine on what grounds Professor Burmeister ascribes to me the opinion that the ribs are immoveable, and why he affirms that they are wholly wanting- in the London skeleton. What I have stated is, that the first rib is immoveable ; and so far from the ribs being wholly wanting, I have particularly mentioned their presence *, and have alluded to the characters of the first *f\ Professor Burmeister adds that I am in error in supposing that the dorso-lumbar vertebrae were immoveably united. I believe, however, from Professor Burmeister’s own words, that my description is substantially accurate. These words are : — “ There exists a moveable place between the dorsal and the lumbar vertebrae, though the mobility is not so complete as that of the three first anchylosed vertebrae upon the following ones. In this part, the skeleton of Buenos Ayres presents a complete column, formed by eleven vertebrae incorporated into a solid piece, of a very peculiar form, with three crests in the upper part, the two lateral of which bear the ribs in articular exca- vations. The total number of dorsal vertebrae and of ribs is therefore fourteen. Then follow on these the lumbar vertebrae, all anchylosed together and immoveably united with the sacrum.” I do not venture to doubt the accuracy of Professor Burmeister’s description of the specimen under his own eyes ; but nevertheless, as will be seen by-and-by, it is also true that the account I have given of the Glyptodon in the College Museum is quite accu- rate. And indeed, as Professor Burmeister admits that all the dorsal and all the * Proceedings of the Royal Society, Z. c. p. 317. t Ibid. p. 319. PROFESSOR HUXLEY ON THE OSTEOLOGY OP THE GENUS GLYPTODON. 43 lumbar vertebrae respectively were anchylosed together, with only an imperfect mobi- lity at the junction of the two solid masses, I do not see how, in any important respect, his view of the matter differs from mine. The last criticism which Professor Burmeister offers, refers to what he terms my error in ascribing five toes to the fore foot, when, as he affirms, it possesses only four. Pro- fessor Burmeister states that I have figured five toes to the foot of the Glyptodon in the lecture already referred to ; but he is mistaken ; only four toes are there represented, numbered, according to the digits of the typical foot which they represent, 2, 3, 4, 5. In the ‘ Proceedings’ (p. 325) I have expressly stated — “The trapezium possesses only a very small double articular facet on its palmar face. If this gave support to a metacarpal, it must have been very small ; and as at present neither it nor any of the hallucal phalanges have been discovered, it is possible the pollex may have been altogether rudimentary. In any case the pollex must have been so much smaller and more slender in proportion than that of Dasypus, that the animal must have had a practically tetradactyle fore foot.” The errors, therefore, to which Professor Burmeister adverts, appear to me to arise to a great extent from his not having rightly comprehended my statements ; and in part, it may be, from our having to deal with different objects. Part II. — Description of the Skeleton of Glyptodon clavipes, Owen ( Hoplophorus Selloi, Lund 1). The materials which have been available for the following description of the osteology of Glyptodon are, in the first place, the skeleton referred to in the previous section as having been presented by Senor Terrero to the Royal College of Surgeons; secondly, the detached parts which have been already described by Professor Owen, and are now contained in the Museum of the Royal College of Surgeons ; thirdly, some fragmentary specimens in the British Museum ; and fourthly, photographs of a skeleton of Glyptodon in the Museum of Turin. The two latter sources of information, however, are of altogether secondary importance, and will be adduced merely in confirmation of the results obtained from the study of the two former series of materials, — in treating of which, I shall speak of the fragments of Glyptodon clavipes described by Professor Owen as the “ type specimen,” and of the skeleton presented by Senor Terrero as the “ new specimen.” § 1. Description of the Skull of Glyptodon clavipes. In the new specimen * the anterior part of the skull, from a line drawn transversely, immediately behind the zygomatic processes, to the anterior end of the snout, is in a remarkably good state of preservation — the boundaries of the anterior nares, the antero- lateral parts of the maxillary bones, the nasal, and the fore part of the frontal, bones being quite uninjured. Behind the imaginary transverse line in question this cranium * Plate IY, figs. 1 & 3, Plate V., and Plate YI. figs. 1, 2, 4, & 5. 44 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. is very imperfect — the entire roof and sides, and the greater part of the base of the skull being absent, while a small portion only of the sphenoidal region is preserved. Of the facial bones, those entering into the palate are preserved almost in their entirety, and one ramns of the lower jaw is nearly complete. This skull therefore supplies almost all those parts which were wanting in the cranium of the type speci- men, in which the whole of the roof of the skull, from the nasal bones to the supra- occipital inclusive, most of the exoccipital, alisphenoidal, and orbitosphenoidal regions of the lateral walls, and of the basioccipital, basisphenoidal, and presphenoidal parts of the base, together with the temporal bones, are in good condition, while the premax- illary, maxillary, and palatine bones, with the mandible, are absent. In order to give a tolerably complete view of the structure of the skull, I shall, in the first place, describe that of the new specimen ; I shall next proceed to a comparison of the parts common to this fossil and the skull of the type specimen, in order to demonstrate the specific identity of the two ; and then I shall endeavour to supply what is wanting in the new specimen by information derived from the study of the type. The skull of the new specimen of Glyptodon clavipes. — The anterior nares have a trapezoidal form, the upper of the two parallel sides of the trapezoid being nearly three times as long as the lower, so that the two lateral boundaries converge from the roof towards the base of the nares (Plate VI. fig. 1). The upper boundary of the anterior nares is formed by the anterior edges of the thick nasal bones, which are bevelled obliquely from below upwards, and so rounded off late- rally that the contour of the two forms a large arc of a circle, the chord of which measures 3-4 inches (Plate IV. fig. 1). The upper surface of each nasal bone is rough and perforated by many vascular foramina, which open forward ; and the two nasal bones are separated by a suture, which can be traced backwards in the middle line for 2'2 inches, and then comes to an abrupt termination. I presume that the extent of this suture indicates the distance to which the nasal bones reach backwards ; but there are no traces of the nasofrontal, or nasomaxillary sutures. The middle of the under surface of each nasal bone presents a strong, rounded, longitudinal ridge, on each side of which there is an equally distinct concavity, and the apposed slightly thickened inner edges of the two nasal bones form a third, less marked, median ridge. The expanded upper edge of the perpendicular plate of the ethmoid embraces this middle ridge, while the nasal turbinal bones are continuous with the ridges on each side of it (Plate VI. fig. 1). A well-marked notch, or sinuosity, separates the upper from the lateral contour of the anterior nares ; and, about an inch below this, the inner surface of the outer wall of the nostril exhibits a rounded elevation or thickening. Still more inferiorly, the wall of the nasal cavity is somewhat excavated, so as to present a thin anterior edge, which passes into the trough-like lower boundary, constituted by the palatine portions of the prsemaxillse. These are separated throughout their whole length in the middle line (a distance of rather more than an inch) by a fissure less than one-tenth of an inch in diameter posteriorly, but twice as wide in front, the prsemaxillse becoming more PEOFESSOE HUXLEY ON THE OSTEOLOG-Y OF THE GENUS GLYPTODON. 45 distant by the divarication of their anterior and internal angles. The thick and rough anterior edges of the preemaxillee diverge obliquely from one another, both forwards and outwards and upwards and outwards, at a very obtuse angle, the interval between their anterior and external terminations amounting to 1-5 inch (Plate IV. fig. 3). Viewed laterally, the anterior ends of the nasal bones are seen to project about half an inch beyond the upper part of the lateral boundary of the nares, which slopes upwards and backwards with a slight forward concavity from the palatine portion of the preemaxilla (Plate V. fig. 1). The nasal cavity is divided, longitudinally, by a very strong osseous septum, which extends to the posterior end of the premaxillary fissure below, and to within 0-4 inch of the anterior contour of the nasal bones above (Plate VI. fig. 1). This septum terminates, in front and below, in a thin jagged edge; but above, it expands into a broad plate T2 inch wide, presenting a deep and broad notch above, into which, as I have previously stated, the conjoined median edges of the nasal bones are received. The septum is about 2'6 inches high in front; and of this height 2-2 inches, or about five-sixths, is formed by the perpendicular plate of the ethmoid, while the rest belongs to the vomer (Vo.). The ethmoidal plate is thin in front, thicker in the middle, and thin again posteriorly. The lower half is somewhat excavated on each side, from above downwards ; it ends in an inferior edge, or rather surface, 0-7 inch in diameter, anchylosed with the upper edge of the vomer, which has, in front, a corresponding thickness. The floor of the anterior part of the nasal cavity (i. e. as far as the level of the fourth alveolus) is concave from side to side, and convex from before backwards, its convexity corresponding with, but being much more strongly marked than, the concavity of the arched roof of the palate. At about 2 inches from the anterior boundary, a sharp longitudinal ridge commences upon the floor of each division of the nasal cavity, and extends backwards, for a distance of about 1| inch, to the summit of the arch formed by that floor (Plate VI. fig. 1, a). Each ridge has a sloping convex external face, and a perpendicular concave inner face, 0-2 inch high. Between the latter and the side of the vomer, which is excavated for a corresponding distance from above downwards, lies a canal, a quarter of an inch wide, and open above and at its ends. The- floor of each nasal chamber rises gradually into its lateral wall ; and upon this, about three-fourths of an inch from the floor, appears a ridge which, at about an inch from the antero-lateral margin of the nostril (or just above the anterior end of the ridge on its floor), passes backwards into the commencement of the inferior spongy bone (Plate VI. fig. 1, b ). The root of attachment of this bone to the maxilla is, as usual, a narrow and thin, though long, bony plate, which on its free, or inner, side is continued into two scroll-like lamellae, an upper and a lower. The upper scroll comes much further forward than the lower, and is a stout plate of bone, slightly concave inwards and convex outwards. In front, it ends in a thin free edge. Superiorly, its margin is folded over outwards, and becomes anchylosed with the lateral wall of the nasal chamber. The inferior lamella commences about an inch behind the superior one. It is thick, 46 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. convex inwards and concave outwards, and its inferior edge becomes much thickened as it curves outwards. It is attached to the maxilla by an anterior and superior thin, and a posterior and inferior, much thicker, plate of bone. Three passages, consequently, lie between the lateral walls of the nasal chamber and the ‘ scrolls ’ of the inferior turbinal, — an upper, long, narrow, and flattened from side to side ; a middle, reniform in section ; and an inferior, rounded in contour. The ridges upon the under surfaces of the nasal bones are continued, as I have stated above, into two thick plates of lamellated bone (Plate VI. fig. 1, c), which increase in depth from before backwards and pass into what are, probably, the superior ethmoidal turbinals. Their inner surfaces are flattened and parallel with the sides of the perpendicular plate of the ethmoid. Their outer surfaces, irregularly concave, are separated by but a narrow interval from the concave faces of the superior scrolls of the inferior turbinal bone. The posterior view of this fragmentary skull (Plate VI. fig. 2) affords a further insight into the arrangement of the bones which contribute to the formation of the olfactory chambers. The aspect presented is that of a transverse section taken just in front of the anterior end of the cranial cavity. The comparatively thin posterior part of the lamina jperpendicularis of the ethmoid (Fth) is seen abutting, above, against the frontal bones (Fr), and, below, becoming connected with the vomer (Vo), the posterior nearly straight free edge of which bone ends on the floor of the nostrils, at the level of the posterior margin of the third molar tooth, and thence slopes obliquely upwards and backwards. The ethmovomerine plate, however, is not free from all lateral' connexion with the tur- binal bones, as is commonly the case ; but a thin plate of bone, convex forwards and concave backwards, passes, on each side, from the vomer and the lamina perpendicularis to the lateral masses of the ethmoid. The inner surfaces of these are marked by broad flattened grooves, directed forwards and downwards, and separated by sharp ridges, which, in the recent state, were probably produced into delicate plates of bone. The lower portion of the lateral mass of the ethmoid, which represents the middle turbinal, is continuous with the inferior turbinal. The upper portion, representing the superior turbinal, is similarly continuous with the nasal turbinal. The superior tur- binal of each side forms the floor of a considerable cavity (Plate VI. fig. 2), which is walled in, externally and above, by the frontal bone, and represents a frontal sinus. A rounded dome (a) of bone projects backwards from the anterior wall of this cavity, which appears to communicate with the nasal fossse only by a few foramina, situated around the margins of the dome. The palate (Plate IV. fig. 3) is singularly narrow, seeing that its length, measured in a straight line, is about 9^ inches, while its width, between the outer edges of the alveoli, nowhere exceeds 3 inches. The longitudinal contour of the palate is concave anteriorly, convex posteriorly (Plate V. fig. 1). The crown of the arch of the anterior concave portion is opposite the hinder margin of the third alveolus ; from thence the roof of the palate slopes, downwards and forwards, to the free premaxillary edge. From the same point it slopes, downwards and backwards, to the level of the hinder margin PROFESSOR HUXLEY ON THE OSTEOLOGY OE THE GENUS GLYPTODON. 47 of the fifth alveolus, while behind the sixth it ascends, somewhat abruptly, to its pos- terior termination. Throughout the posterior two-thirds of its length, the palate is slightly and evenly concave from side to side ; but, from the third alveolus forwards, its middle part rises to form a median convexity, which ends by a rough, abruptly truncated ridge (Plate IV. fig. 3, a ), behind the premaxillary fissure. It forms, in fact, the posterior boundary of a transverse fissure ending in a notch, or short canal, at each extremity, which represents the anterior palatine foramen, and which, taken together with the intermaxillary fissure, simulates very closely the form of a T. A deep groove (&) separates the raised part of the palate from the alveolar margin, and ends, behind, in a canal which burrows into the substance of the bone opposite the anterior edge of the third tooth on both sides. On the left side, however, the hinder part of the groove is bridged over by a bar of bone. Large foramina are situated, along a line continuing the groove, opposite the third and fourth alveoli ; but no such apertures appear in the posterior part of the palate until quite its hinder extremity is reached, when, on each side, two crescentic fossae (Plate IV. fig. 3, c), wider in front than behind, lie on the inner side of the last alveolus, and appear to separate the palatine from the maxillary bones. They end caecally above. The bony palate exhibits no distinct sutures, except a trace of a maxillary suture behind the anterior palatine foramen, and of a palatine suture, which widens behind into a cleft, separating the arcuated, divergent inner and posterior boundaries of the palatine bones. The free surfaces of the bony masses which bound the palate, poste- riorly, are so smooth and unbroken, that I suspect the pterygoid bones must be repre- sented in them. As the palate presents very nearly the same width throughout, while the roof-bones of the skull are always much wider than it, it follows that any vertical section of the skull, perpendicular to its long axis, in the palatine region, would exhibit a trapezoidal form, like that of the anterior nares — the predominance of the upper side over the lower being still more marked. But in the antorbital region the roots of the zygomatic processes are so large, and stand out so much from the sides of the head, that the skull, viewed in front, looks almost like a cube, with its lower face produced forwards and downwards into a truncated wedge (Plate VI. fig. 1). The only trace of a suture visible upon any part of the sides of the facial wedge is an almost obliterated one (Plate V. fig. 1, a), which runs from a slight notch, opposite the level of the anterior palatine foramen and in front of the first alveolus, upwards and slightly backwards, and marks off the ascending process of the prsemaxilla from the maxilla. This ascending process, very narrow in the middle, widens above and joins the nasal bone, so that the circumference of the anterior nares is completed by the prsemaxillse and nasal bones only. Opposite the second and third alveoli, the maxillary bone, as I have stated; above, widens out and expands into the root of a stout zygomatic arch, whence a process, nearly 6 inches long by 2 inches wide, passes directly downwards. The process is much flattened from before backwards (Plate VI. fig. 1), and is arched from above downwards (Plate V. mdccclxv. i 48 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. fig. 1), so as to be convex in front and concave behind. Its inner edge is thick and rounded, except towards its termination, where it presents some slight irregularities or cligitations. The outer edge is comparatively thin and rugose ; it is bevelled off inte- riorly, and more obliquely on the right side than on the left. The inner part of the front face of the process looks almost directly forwards, and is very smooth ; but the outer part of that face looks outwards more than forwards, and is rugose (Plate YI. fig. 1). The hinder, concave face of the process (Plate VI. fig. 2) is divided by an oblique ridge (b), which passes from its superior and external to its inferior and internal angle into two areee — an inner, smooth, and an outer, rough and tuberculated. The superior and external part of the process, where it was doubtless continued into the zygoma, is evidently fractured. The root of the zygoma is perforated near its origin by a large, oval, infraorbital canal, the lower edge of which is rather more than an inch distant from the lower margin of the root of the zygoma. The canal is short, and is directed forwards and outwards. The lachrymal foramen is a round aperture, placed upon the anterior edge of the orbit, T6 inch above the infraorbital canal (Plate V. fig. 1, b). The internal walls of eight alveoli, on each side, are preserved. The external walls <of the anterior four upon the left side, and of the anterior three upon the right side, •are almost entire ; but, posteriorly, the external walls of all the other alveoli, upon each side, are broken away (Plate V. fig. 1). Measured in a straight line, the eight alveoli occupy a space of 8 inches, and each alveolus is, on an average, 0*9 inch long. The teeth which occupy the alveoli are sen- sibly equal in long diameter ; but the anterior tooth is much narrower than the others, measuring only 0‘35 inch in this direction, while the other teeth have a transverse diameter of 06 inch, or nearly double that of the first. None of the teeth are entire upon the right side. Of the left series, the crowns of the first, third, fourth, and sixth are in very good condition, while the second is much damaged ; of the fifth, only the middle lobe exists, and of the seventh only the two ante- rior lobes (Plate IV. fig. 3). The alveoli are exceedingly long, and the outer walls of the third and fourth, on each side, are so much broken away, that the whole length of their alveoli can be observed and measured. The fourth is 4*5 inches long, and bends outwards and forwards as it passes upwards, to terminate nearly on a level with the lachrymal foramen. The tooth which filled the alveolus must have had a corresponding length and curvature ; for the two longitudinal ridges of bone, which partially subdivide the alveolus into three chambers near its free end, are continued quite up to its closed extremity, and are lined by a shell of dental substance, which gradually thickens below and becomes continuous with the body of the tooth (Plate Y. fig. 1. 4, 4'). The third alveolus presents the same general curvatures as the fourth, but is inclined somewhat further outwards at its upper end, which lies close to, and about an inch above, the hinder end of the infraorbital foramen. PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 49 The wall of the upper end of the first alveolus has been broken through on the right side. It lies on a level with the upper edge of the infraorbital foramen, and imme- diately behind the premaxillary suture. From what remains of the hinder alveoli and teeth, I suspect they become more and more nearly straight posteriorly. The external vertical contour of each tooth must be very similar to that of the max- illary surface between the upper end and the edge of the alveolus. The lateral faces of all the teeth are divided by two longitudinal grooves, placed opposite to one another on the two sides of each tooth, into three lobes. In the first tooth these grooves are very shallow, so that the thickness of the tooth, between the grooves, is far greater than the depth of a groove. In all the other teeth, the thickness of the teeth between the grooves, or of the isthmus by which the lobes of each tooth are connected, is much less than the depth of a groove. The view of the palate (Plate IV. fig. 3) shows that lines following the planes of the anterior surfaces of each of the four anterior teeth are directed inwards and forwards ; while in the sixth and seventh teeth, if not in all four posterior ones, such lines are directed inwards and backwards. The anterior surfaces of all the teeth, but the first, are concave, the posterior surfaces convex. The grinding-surfaces of all the teeth are directed a little outwards as well as downwards. Each surface is ridged in the middle and surrounded by a thin raised margin, and the general arrangement of the ridges is such that one is median, traversing the longitudinal axis of the grinding-surface, and three are disposed at right angles to these, in the longitudinal axes of the three lobes. The transverse ridges are continuous with the longitudinal, where they cut it (Plate V. figs. 3 & 4). Sometimes a transverse ridge may be bifurcated at its extremity, or accessory branch- lets may be given otf from the transverse, or from the longitudinal, ridges. A large pulp-cavity occupies the upper portion of each tooth ; but as its walls begin sensibly to thicken at about the junction of the upper and middle thirds of the tooth, the pulp-cavity diminishes in a corresponding ratio, and, rather below the middle of the tooth, it becomes obliterated. The Mandible* . — The lower jaw of Glyptodon is very remarkable, partly on account of the trough-like projection of the symphysis, but more especially by reason of its great height in relation to its length. The height, as measured from any horizontal surface on which the jaw is allowed to rest, to the summit of the articular condyle, is 9’25 inches; * Leaving aside for the present M. Nodot’s “ Schistopleuron,” the only fragment of the lower jaw of Glyp- todon clavipes yet described is that mentioned in the Catalogue of the Royal College of Surgeons under “ No. 517. A fragment of the anterior part of the left ramus of the lower jaw, including portions of the sockets of the anterior teeth. The first is small and simple, and is situated close to the anterior termination of the dental canal ; the second socket shows, by the two prominent vertical ridges on its anterior and posterior walls, that the tooth which it contained had the fluted form characteristic of the genus ; the third socket, which is the most complete, differs from the preceding in a slight increase of size, and it shows that the tooth was implanted by an undivided base of considerable length, and of the same size and form as the exposed part or crown.” i 2 50 PEOFESSOE HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. while the length, measured in a straight line, from the symphysis to the angle of the jaw, is not more than 10 ‘75 inches. The horizontal ramus is very deep and thick, mea- suring about 3-25 inches vertically by 1-5 inch in thickness, while the ascending ramus is 3'5 inches wide by about 09 inch thick at thickest (Plate V. fig. 2). The anterior end of the mandible is 2*9 inches wide and abruptly truncated, ending in a rugose edge, nowhere more than half an inch thick, which, at its extremities, bends round at a right angle into the upper margins of the rami (Plate VI. fig. 5). These, thick and rounded, ascend somewhat towards the first alveolus, which is 2-25 inches distant from the anterior end of the ramus. The symphysis, 5 '7 inches long, appears to be formed, by the sutural union, and not by the anchylosis of the rami ; but the bone has been so broken that a large aperture occupies the middle of the symphysial space (Plate VI. figs. 4 & 5). The exit of the inframaxillary canal is nearly half an inch wide, and is situated If- inch below the upper margin of the jaw, and directly beneath the anterior boundary of the first alveolus. The anterior, or symphysial, contour of the mandible slopes, with a slight forward concavity, obliquely downwards and backwards to the level of the foramen ; and is then continued, almost straight, or with a slight anterior convexity, to a point nearly in the same vertical line as the hinder edge of the third alveolus (Plate V. fig. 2). The symphysial face is convex from side to side inferiorly, and gradually widens until, at its hinder end, its breadth amounts to 5 "5 inches. Its outer boundary is formed by an obtuse longitudinal convexity, which runs along the middle of the outer face of the horizontal ramus, and dies away, posteriorly, at the commencement of the ascending ramus. From this ridge, or convexity, the summit of which corresponds with the greatest outside breadth of the jaw, the outer surface of the ramus slopes upwards and inwards to its alveolar margin (Plate VI. fig. 4). The inner face of each horizontal ramus is slightly concave from above downwards, passing, in front, into the excavated upper surface of the symphysis. The general contour of the anterior half of the alveolar margin of the mandible is slightly convex upwards, in correspondence with the concavity of the opposed region of the maxilla (Plate V. fig. 2). The posterior half of the same margin is broken away ; but it may be assumed that it was concave upwards, answering to the downward con- vexity of the hinder part of the maxillary alveolar edge. The inner edges of the alveolar margins of the two rami are 2 inches apart. In the left ramus the series of alveoli is tolerably well preserved for 5^ inches, or to a point behind the anterior edge of the ascending ramus. From the character of the broken surface behind this point, however, it is obvious that the series of alveoli was continued along the inner surface of the ascending ramus, very nearly to the angle of the jaw, and considerably behind a line let fall perpendicularly from the articular condyle — an arrange- ment which, so far as I am aware, has no parallel among Mammalia (Plate VI. fig. 5). As the whole length of the series of mandibular alveoli is about 8 inches, it is pro- bable that the number of teeth was the same below as above, or eight on each side. PROFESSOR HUXLEY OX THE OSTEOLOGY OE THE GENUS GLYPTODON. 51 The external surface of the perpendicular ramus of the mandible is rugose, slightly convex from above downwards and from side to side, while its internal surface exhibits a corresponding concavity, which is exaggerated below by the inward projection of the posterior alveoli, and is divided by an elevation of its surface, which ascends obliquely from the alveolar margin towards the coronoid process, into an anterior and a posterior moiety. The apex of the coronoid process is broken away upon each side, but it seems not to have extended beyond the level of the articular condyle, from which it is sepa- rated by only a shallow notch. The hinder margin of the perpendicular ramus, which is very thin inferiorly, thickens •with the rest of the bone superiorly, and ends above in a transversely elongated condyle, which projects further upon the inner than on the outer side of the plane of the ramus (Plate V. fig. 2°). Viewed laterally, this condyle has the form of a wedge, the base of which is O’ 7 inch broad; its hinder face being slightly concave, while its anterior face, convex from above downwards, and slightly concave from side to side, looks forwards and upwards (Plate V. fig. 2). It is this face which bears the surface for articulation with the squamosal element of the skull, and is indeed coextensive there- with. The surface in question is 1*25 inch wide from side to side, and 06 inch broad or from above downwards, and is tolerably smooth, but not very different from the adjacent parts of the condyloid process. The remains of five successive anterior teeth are observable in the alveoli of the left ramus of the mandible, and the socket of the sixth is clearly defined. Behind it, for a space of 1'8 inch, the inner wall of the ramus is broken away so completely that no trace of any alveolus is left. On the right side, the bone is nearly in the same state, but at .a distance of 7'6 inches from the anterior edge of the most anterior alveolus, I observe a smooth vertically grooved surface of bone, which is situated nearly in the same plane as the outer walls of the other alveoli, and which I conceive to be part of the outer wall of the last alveolus. The teeth of the mandible present the same trilobed form and other general charac- ters of those of the maxilla, but very few are in a sufficiently entire state to furnish materials for description. The first and second, on the left side, and the third, upon the right side, however, have their grinding-surfaces entire, or nearly so (Plate VI. fig. 5). The grinding-surface of the first tooth (left side) is 085 inch long and 04 inch wide at- widest. It has a very different form from the first tooth of the maxilla, the two posterior ridges of the outer surface being much more developed. The grinding-surface of the second tooth (left side) measures 09 inch by 045 inch; its outer ridges and grooves are also the better marked. The posterior surface of the tooth is fiat or a little concave, and its plane is directed obliquely outwards and back- wards. The grinding-surface of the third tooth (right side) is l-05 long, and the isthmuses which unite its prisms are much narrower than in the second tooth. Both the anterior and the posterior faces of the tooth are curved. The grinding-faces of all these teeth 52 PROFESSOR HUXLEY ON THE OSTEOLOGY OE THE GENUS GLYPTODON. are inclined a little inwards as well as upwards, reversing the direction of the grinding- faces of the upper teeth. The mandibular teeth seem to have been nearly straight, without either external or internal concavity. Their long axes are inclined rather backwards as well as downwards. The alveolus of the fourth tooth, on the right side, is laid open ; and I judge from it that the fourth tooth must have had a length of about 3^ inches ; and the others might have had the same dimensions, except the first, which is certainly shorter, probably not exceeding 2^ inches. A considerable canal traverses the right ascending ramus from behind and below, up- wards, forwards, and outwards. Its external aperture, oval, 0*3 inch wide, lies upon the outer face of the ramus, on a level with the alveolar margin, and rather nearer its anterior than its posterior edge (Plate V. fig. 2). The inner end of the canal, which is T7 inch long, terminates in the broken cancellous structure, on the outer side of what appears to be the remains of the last alveolus. I cannot certainly discern any remains of a corresponding canal in the left ascending ramus. All that remains to be described in this skull is a fragment of the basis cranii, con- sisting of part of the anchylosed basi- and pre-sphenoid bones. The presphenoid (Plate VI. fig. 2) is remarkable for the strong crest or spine into which the middle of its upper surface is produced, and which was not improbably continued into an ethmoidal crista galli. The posterior apertures of the passages for the optic nerves are ellipses, with their long axes directed upwards and outwards ; they are about a quarter of an inch in dia- meter, and are continued into two canals, which are traceable, outwards and upwards, for about an inch in the substance of the orbitosphenoids. On each side, below and external to the optic foramina, are strong grooves which formed the inner portion of the confluent foramen rotundum and sphenorbital fissure. The front face of the presphenoid and the roots of the orbitosphenoids are excavated by deep sphenoidal sinuses. Comparison of the Skull of the present specimen with that of the typical Glyptodon clavipes. — The principal parts which exist in both skulls, and may therefore serve as terms of comparison, are, 1, the nasofrontal region of the roof of the skull; 2, the descending zygomatic processes ; 3, the alveoli ; and 4, the basi- and pre-sphenoid. 1. The resemblances in size and general configuration between the nasofrontal regions of the two skulls are so obvious that I need hardly dwell upon them at any length. The present specimen differs from the type in the more rounded contour of the nasal bones, in the persistence of the nasal suture, in the less rugosity and squareness of the supraorbital prominences, and in the far less marked definition of the temporal ridges ; but none of these characters appear to me to have more than an individual import- ance, and I am inclined to suspect that they depend largely on the less advanced age of the present specimen. 2. The zygomatic processes have the same length (measured from the infraorbital fora- men) in each case. They are slightly narrower in the type specimen ; in other respects PROFESSOR HUXLEY ON THE OSTEOLOGY OE THE GENUS GLYPTODON. 53 the zygomatic processes of the two specimens do not differ more than those of opposite sides in the same specimen. 3. In the typical specimen the upper ends of the three anterior alveoli, on each side, are preserved; they occupy just the same space as the three anterior alveoli of the present specimen. 4. The presphenoid in the type has the same crest, and the inner ends of the optic foramina are precisely the same distance apart. When to these correspondences we add that the distance from the front edge of the nasals to the level of the posterior edges of the supraorbital prominences is the same in both skulls, and that the lower jaw of the new specimen would fit very fairly on to the typical skull, it will, I think, be admitted that there is sufficient evidence of the specific identity of the animals to which the two skulls belonged, and that the imperfections of the new specimen may be supplemented by the evidence afforded by the typical example. Further data as to the Cranial Structure of Glyptodon furnished by the typical skull. — Professor Owen (‘ Catalogue of Fossil Mammalia and Aves,’ p. 384) thus describes the fragmentary skull of the typical specimen of Glyptodon clavipes : — “ The occipital condyle (a) presents a convexity in the vertical direction, which describes more than a semicircle, and is slightly convex transversely, but is narrower in that direction than it is in the Mylodon : it is directed in the Glyptodon backwards and obliquely outwards. The occipital foramen (b) is very large and transversely elliptical ; its plane is inclined from below upwards and backwards 20° beyond the vertical line. The anterior condyloid foramen (c), though large, is relatively smaller than in the Mylo- don, and is situated close to the anterior border of the condyle. The depression for the digastric muscle ( d ) is perforated and separated from the condyle by a wider tract of the paroccipital (e) than in the Mylodon ; and the petromastoid ( f ) below the digas- tric depression presents a rough convexity, bounded posteriorly by a transverse ridge of the paroccipital instead of the hemispherical depression for the articulation of the stylo- hyoid bone which characterizes the skull of the Mylodon . The basioccipital ( g) pre- sents a median smooth concavity and two lateral rough depressions, which are continued on to the basisphenoid (A), and indicate the insertion of very powerful ‘ recti-capitis antici majores’; the obliterated suture between the basioccipital and basisphenoid forms a rough transverse ridge. The inequalities of this part of the basal region of the skull present a striking contrast to the broad smooth and even tract which the same part forms in the Mylodon. The sides of the concave under surface of the basisphenoid are bounded by longitudinal ridges, which have been broken off in the specimen. The petrous bone terminates by a prismatic pointed process in the foramen lacerum (i), which here gives passage both to the jugular vein and internal carotid. The foramen ovale (k) is circular, and of the same size as the anterior condyloid foramen. The fora- men rotundum (l) is one inch and a half in advance of the foramen ovale, and opens with the commencement of a deep and long groove, which traverses the base of the 54 PROFESSOR HUXLEY ON THE OSTEOLOGY OE THE GENUS GLYPTODON. pterygoid processes in the direction towards the antorbital foramen. The base of the zygomatic process supporting the articulation of the lower jaw (m) is brought much nearer the occiput than in the Mylodon , and is separated from the petromastoid by a deep excavation, perforated by wide apertures that seem to communicate with the tym- panic cavity. The articular surface for the lower jaw is well defined, narrow in the axis of the skull, much extended transversely, gently convex in both directions. In the skull of a recent Armadillo ( Dasypus octocinctus ) the articulation for the lower jaw is almost flat, and on a level with the roof of the posterior perforated cavity. In the Prio- nodon {Dasypus gig as, Cuv.) the articular surface is slightly concave, and extends longi- tudinally forwards from the posterior cavity. The zygomatic process of the malar bone, bounds the outer and fore part of the surface, and extends forwards in the form of a laterally compressed plate of bone, and in the Das. sexcinctus forms a slight angular projection below the antorbital perforation. In the Glyptodon , the articulation for the lower jaw more resembles that in ordinary Pachyderms, and is thus conformable with the deviation from the Edentate structure manifested by the bones of the foot. But the most remarkable characteristic of the skull of the Glyptodon , by which it differs from the existing Armadillos and approaches the Megatherioids, is the long and strong process (n) which descends from the base or origin of the zygomatic process of the maxillary bone. This process is compressed, but in the opposite direction to that in the Mylo- don., viz. from before backwards, instead of from side to side ; it measures five inches in length from the antorbital perforation, one inch and three-fourths in breadth across the middle : the outer margin is entire, and as if folded back ; the lower half of the inner margin is slightly notched, the extremity of the process curves backwards. Both ante- rior and posterior surfaces bear strong marks of the attachment of muscular fibres. “ The small remaining portion of the maxillary bone- on the inner side of this process shows portions of three deep sockets (o o ) of the same diameter throughout, indicating the implantation of molar teeth by a single excavated base, and showing two longitudinal ridges on both the outer and the inner side, which proves the teeth to have had the same fluted exterior which they present in the lower jaw, and of which the generic name of Glyptodon is expressive. The fractured anterior part of the basis cranii shows the large cavities for the olfactory bulbs, and the remains of a very extensive cribriform plate, the organ of smell being very largely developed. “ The posterior, or occipital surface of the skull slopes forward from the plane of the occipital foramen at an angle of 45° ; in the small existing Armadillos it is vertical ; in the Glyptodon it is divided by a strong median vertical ridge, and separated by a sinuous thicker transverse ridge from the upper surface of the skull. The posterior half of this region of the cranium is marked by the ridges bounding the origins of the temporal muscles, which almost meet along the middle or sagittal line. Part of the lambdoidal suture is seen at p ; the other cranial sutures are obliterated. The temporal fossae are pierced by numerous large vascular foramina. The anterior parts of the temporal ridges (g) diverge to the posterior angle of the supraorbital ridges. The frontal or inter- PROFESSOR HUXLEY ON THE OSTEOLOG-Y OF THE GENUS GLYPTODON. 55 orbital part of the upper surface of the cranium is broad and nearly flat, smooth, and slightly concave at its posterior half, slightly convex, rough, and perforated by vascular foramina at its anterior half. The most prominent parts above the orbits are most rugose, and indicate a more intimate adhesion to the superincumbent osseous dermal helmet. The lachrymal foramen (r) is pierced immediately in front of the anterior border of the orbit. “ The difference in the development of the temporal muscles manifested by the Glypj- todon and Mylodon in the position of the ridges in the fossil cranium indicates a corre- sponding difference in the power of mastication and in the density of the alimentary substances habitually selected by each species ; the greater proportion of hard dentine in the teeth of the Glyptodon , and the greater number of the teeth, which appear to have been thirty-two, eight on each side of both jaws, coincide with the characters of the cranium, and support the inferences thence deducible.” It is necessary to make certain additions and qualifications to the above description. If we may be guided in the interpretation of the structure of the auditory region by the analogy of the existing Euphractus , the part which is there termed “ paroccipital” (Plate IV. fig. 5, h) includes the true mastoid; the “perforated depression for the digastric muscle ” (Plate IV. fig. 5,f) is the external auditory meatus; and that which is termed “ petromastoid below the digastric depression ” (Plate IV. fig. 5, g) is part of the tympanic element of the temporal bone. It would appear that, as in Euphractus, the tympanic bone sends a process outwards and backwards, the extremity of which comes into contact with the pars mastoidea, and so bounds the external auditory meatus externally and below ; while it leaves between itself, the proper tympanic bulla, and the pars mastoidea, an aperture which communicates with the external auditory meatus. The latter is remarkably small for so large an animal. The “ bulla,” into which it opened, is broken away ; but it is probable that a considerable part, if not the whole, of the rugose spaces supposed above to be for the insertion of “recti capitis antici,” mark the place where the thick inner walls of the bullae impinged upon the basioccipital. The fenestra rotunda is visible upon the under surface of the pars petrosa as an oval aperture 0T5 inch wide, the long axis of which is directed almost transversely to that of the skull. The fenestra ovalis , smaller, appears above the fenestra rotunda. The proper carotid canal probably traversed the anterior part of the internal wall of the bulla as in the Armadillos; the jugular vein most likely left the skull by a passage between the posterior and internal part of the bulla, the exoccipital, and the periotic. The large apertures perforating the roof of the cavity which is situated behind the articular facet for the lower jaw, do not communicate with the tympanic chamber. They are probably venous channels, and they communicate internally with the cavity of the skull. The articular facet for the lower jaw measures 1*8 inch along its greater, and 0-6 inch along its lesser diameter ; its edges are well defined, and it has a somewhat kidney-shape, the hilus of the kidney being turned downwards (Plate IV. figs. 4 & 5, e). The’general mdccclxv. K 56 PROFESSOR HUXLEY ON THE OSTEOLOGY OE THE GENUS GLYPTODON. aspect of the facet is backwards and downwards, so that, when viewed laterally, its plane appears inclined more than 45° to a horizontal line. The long axis of the facet is nearly at right angles to the axis of the skull, but its outer half has a slight inclination forwards and outwards. It will be observed that the direction of this facet corresponds very well with that of the articular facet on the condyle of the lower jaw of the new specimen ; and the nature of the articulation is such that the lower jaw must have had a purely hinge-like movement in a vertical plane, the doubly curved upper surface of each row of mandibular teeth being brought, with a simply crushing motion, against the correspondingly curved lower surface of the maxillary teeth in each masti- catory act. The “ deep and long groove ” into which, in the above description, the foramen rotun- dum is said to enter, requires particular notice. The foramen rotundum and the spheno- orbital fissure are represented by a rounded aperture 05 inch wide, situated immediately in front and to the inner side of the foramen ovale , and separated from it by only a narrow bar of bone. The small optic foramen, in like manner, lies immediately in front and to the inner side of this aperture, separated from it only by the lower root of the orbitosphenoid. The alisphenoid is prolonged forwards as a broad plate, parallel with the orbitosphe- noid, for about an inch ; and thus the conj oined foramen rotundum and Jissura spheno - orbitalis are continued outwards and forwards by a wide canal of the same length. Ante- riorly, the alisphenoid ends in an arcuated free edge, and so forms the hinder part of the outer lip of a groove open inferiorly, the inner wall of which is constituted by the lateral mass of the ethmoid. The front part of the outer lip of the groove, separated from the other by a slight interval, is formed by a strong descending vertical plate of the frontal bone, ending below in a rugose edge, thicker behind than in front, which sweeps upwards and forwards towards the posterior part of the infraorbital prominence. It ceases at about three-quarters of an inch from that part. The optic foramina are prolonged into canals directed forwards and outwards, each about an inch long, the anterior apertures of which open on the inner wall of the great passage just described, immediately behind the level of the anterior edges of the alisphe- noids. The optic nerves, which could hardly have been more than OT inch in diameter, and were therefore very slender in relation to the size of the animal, must have been con- tinued forwards between the frontal plate and the ethmoid for a distance of at least 3^ inches before they reached the eyeball. Three other apertures are visible in the roof of the groove — one, about as large as the optic foramen, on its outer side, and three-quarters of an inch in front of the proper ante- rior end of the optic canal. The two others are smaller and situated close together, and rather on the inner side, half an inch in front of the former. These may be the ends of canals for the oculomotor nerves. The» remains of the expanded upper edge of a lamina perpendicularis, similar to that PROFESSOR HUXLEY ON THE OSTEOLOGY OE THE GENUS GLYPTODON. 57 described in the new specimen, are visible, attached to the under surfaces of the nasal bones. The inner surface of the right lateral portion of the ethmoid is marked by obliquely diverging ridges of bone, with which the plates of the inferior spongy bone were doubt- less connected. By combining the new specimen with this it is easy to ascertain approximatively the length of the cribriform plate. The former specimen, in fact, is broken through at a distance of six inches from the anterior end of the snout, but its posterior face does not exhibit any notable part of the anterior wall of the cranial cavity. The same distance (6 inches), therefore, measured off upon the roof of the type skull, should give the position of a line beyond which the cribriform plate certainly did not extend anteriorly. From the point thus defined to the anterior edge of the presphenoid is a distance of 1*75 inch, which must therefore represent the maximum length which the cribriform plate could have attained. The distance from the anterior edge of the presphenoid to the level of the posterior margins of the occipital condyles is 4*5 inches. The cribriform plate is rather shorter in proportion to the base of the skull in the Glyptodon than in the ordinary Armadillos, and its anterior part is situated far further back in relation to the antorbital processes. The proper cranial cavity, or brain-case, is small when compared with the whole size of the skull, if the chambers which lodge the olfactory bulbs are left out of considera- tion. It is in fact only 4*5 inches long, 2*5 inches wide at widest, and about If inch high at highest. Its greatest width is situated beneath the occipital ridge, whence it narrows towards the olfactory outlet, which is about 1*25 inch wide. The immediate side walls and roof of the fore part of the cranial cavity are formed by a very thin inner table of bone, separated by a wide air-chamber from the denser and stouter outer table. This air-chamber does not appear to extend back beyond a transverse line connecting the two glenoidal facets. Mr. Flower has obtained a cast of the cranial cavity, from which one is enabled to form an idea of the shape and size of the brain. The proportionally large cerebellum exhibits a prominent vermiform process, and is completely uncovered above by the cerebral hemispheres. The latter are quite smooth, and their upper contour is much arched, while their sides are flattened, and approach one another anteriorly. The absence of convolutions in the brain of so large an animal, together with the small absolute mass of the organ, leads one to suspect a great absence of intelligence in the Glyptodon. k 2 58 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. Measurements of the Skulls. A. The new specimen. inches. Total length of the palate in a straight line 9*50 Width between the inner edges of the alveolar series T75 Width between the outer edges of the alveolar series, opposite third tooth 2*95 „ 5j „ „ last tooth . 2*8 „ „ „ „ first tooth . 2*6 Hinder edge of the last alveolus in front of the posterior nares . . . 0-5 Outer edge of the malar process to the centre of the palate . . . . 5’5 The extreme breadth of the skull therefore = 11*0 Vertical height of skull from frontal bones to palate at fourth tooth . . 6*0 From end of outer edge of orbit to the same point on the opposite side . 7*2 Summit of the frontal region to the ends of the malar processes . . . 9-5 Mandible : — Extreme length from the symphysis to the angle 10*7 Extreme height from the summit of a condyle to a flat surface on which the jaw rests 9*3 Depth of the horizontal ramus at the third tooth 3*2 Width at the symphysis 2*9 Width between the inner edges of the alveoli opposite the first tooth # (remains the same throughout) 3*1 Width between the outer edges at the same point 31 Width between the outer edges at the third tooth 3*25 B. The type specimen. Extreme length from nasal bones to the level of the occipital condyles . 12*7 „ „ „ superior occipital ridge . . . 105 Breadth at the front part of the orbits 6*8 „ at the interorbital constriction 4*3 „ across the occiput, about 5*8 Height of the occiput . 2-6 Distance between the inner edges of the articular surfaces for the condyles of lower jaw 4*25 § 2. The Vertebral Column. The remains of this very interesting part of the organization of Glyptodon are, unfor tunately, in a somewhat imperfect state, though enough exists to demonstrate its alto- gether unique character. PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 59 The Atlas. — Of this bone the mutilated right half is represented in Plate VII. fig. 1, giving the anterior, and fig. 2 the posterior aspect of the fragment. The specimen exhibits rather more than the right half of the lower arch, and rather less than the corresponding portion of the upper arch of the bone. The right lateral mass, with its anterior and posterior articular facets, is almost entire, but the transverse process is broken off close to its origin. The inferior arch is a solid bar of bone with a straight upper and a convex lower contour ; and somewhat thicker in the middle, both from above downwards and from before backwards, than at the sides. A section taken through the median plane of this part of the bone would have the shape of a spherical triangle; the lower or horizontal face convex, the anterior slightly concave, and the posterior and upper also concave. The middle of the posterior and upper face of the inferior arch presents an oval arti- cular facet (fig. 2, a) for the odontoid process of the axis, which, when entire, must have measured about 1-6 inch in width by 0-8 inch in antero-posterior length. It is slightly concave, both from before backwards and from side to side, and is bounded by a well- defined though narrow ridge. The outer end of this facet is half an inch distant from the inner and lower edge of the articular surface for the odontoid vertebra, upon the lateral mass of the atlas (fig. 2, b). This is a reniform surface with its inner and anterior side concave, while the outer and posterior aspect is convex. Its long axis is almost vertical, while the plane of its surface, which is a little concave both from above down- wards and from side to side, is directed obliquely inwards and forwards. Lines drawn through the shorter axes of the two articular facets would intersect one another at a point very slightly in front of the anterior margin of the inferior arch. The foramen for the vertebral artery is situated on the outer side of the facet, opposite the junction of its middle and upper thirds, and nearly on the same level as a tubercle for the trans- verse ligament, situated on the inner side. The foramen (fig. 2, c ) leads into a canal which passes directly forwards, widening as it goes, and traverses the root of the transverse process. In front of this it presents a large oblique aperture, by which, however, it does not terminate. Instead of ending, it makes an abrupt turn upwards through the substance of the superior arch of the atlas, parallel with, and equidistant from, the anterior and posterior margins of that part, and ends by an oblique aperture in the outer part of the roof of the cavity of the atlas, and nearer the occipital than the odontoid edge. The upper face of the lateral mass of the atlas presents an elongated, irregular, transverse aperture, which communicates with the canal, and from the anterior and posterior margins of which broad and shallow grooves are continued. The articular surface for the occipital condyle upon the anterior face of the lateral mass of the atlas (fig. 1) is much more concave from above downwards than that just described ; and as it is neither concave nor convex from side to side, the surface may be regarded as a segment of a hollow cylinder, answering to rather less than half the circumference of such a figure. When the inferior arch of this atlas is made horizontal, this articular 60 PROFESSOR HUXLEY ON THE OSTEOLOG-Y OF THE GENUS GLYPTODON. surface looks forwards and inwards. The inner and lower edges of the opposite occi- pital facets of the atlas must have been separated by a distance of about 1*9 inch. The transverse process of the atlas is, as I have stated, broken off close to its origin ; but the cancellated fractured surface, 2 niches long by more than half an inch wide superiorly, proves that the process was flattened from before backwards, and that it arose from the posterior half of the outer surface of the lateral mass of the bone. The surface of attachment of the process is almost perpendicular to that of the axis of the spinal canal, or, at most, has a very slight inclination from above downwards and for- wards. The general plane of the process, on the other hand, as exhibited by an upper or an under view, is directed backwards and outwards. There are no means of judging how far the process may have extended outwards. The Odontoid and immediately-following Cervical Vertebrae. — The fragment of this region of the vertebral column (figured in Plate IX. fig. 5 from without, fig. 6 from within, fig. 7 from behind, and fig. 8 from below) is composed of the right half of the neural arch of the axis, or odontoid, vertebra, anchylosed together with the arches of the third and fourth cervical vertebrae. It formed the right half of the roof and side walls of the neural canal in this region. The front face of the bone, thick and prismatic, is obliquely bevelled off to a rounded edge, which is concave anteriorly. The outer face is produced above into a tuberosity, the anterior part of which is perforated by a canal which traverses the whole thickness of the bone and opens on its inner face, near its upper end (fig. 5, c , fig. 6, c1). From the tuberosity a small ridge, partly broken away, leads forwards and inwards along the anterior face of the bone. A stouter ridge extends inwards near the posterior margin of the bone, from the same tuberosity. These two ridges were situated upon the proper upper surface of the arch, and probably joined the anchylosed spinous processes. The lower part of the outer face presents a broken surface, with the outer termina- tions of three canals (figs. 5 & 8, d, e,f), the inner ends of which are visible on the inner or under surface of the bone (fig. 6, d, e,f) as they traverse its thickness obliquely from within outwards and downwards. The hindermost of these canals (d) is wide below, but narrows into a fissure above. The second, or middle, foramen (e) is wider, oval, and looks more downwards. The third (f) is much smaller than either of the other two. On the inner face of the bone (fig. 6) the aperture of the posterior canal ( d ) is longest. The middle canal opens upon nearly the same level ; but the third, or anterior, canal takes a much shorter course through the bone, and thus its inner end is on a level below the others. The aperture of the middle canal is situated at about the same distance from the ante- rior margin of the bone as the inner end of that canal ( c , c') which, I have stated, opens externally upon the tuberosity. A little aperture (g) in the same line with these two leads into the substance of the bone, and seems to have no external outlet. Lines drawn through the three apertures referred to, mark off an anterior segment of the bone from a middle segment, which is defined, by a line drawn from the inner end of the posterior canal below to another small aperture ( h ) above, from a hinder segment. PROFESSOR HUXLEY OX THE OSTEOLOGY OF THE GENUS GLYPTODON. 61 The posterior face of the bone exhibits, below, a large round aperture (fig. 7, a), leading into a passage which traverses the posterior canal just described, and debouches into the middle one. Immediately beneath this foramen is a small concave articular surface, apparently a fragment of a much larger one. Superiorly and internally the posterior face of the bone presents a deep fossa (fig. 7, a), bounded above and internally by a concave articular facet, the long axis of which is directed almost at right angles to the long axis of the bone. The facet in question I take to correspond with the posterior oblique process or “ post-zygapophysis ” of the fourth cervical vertebra. The foramen on the posterior face is the aperture of the canal for the vertebral artery. The facet below it is part of an articular surface upon the inferior or “ capitular ” division of the transverse process, which is characteristic of the cervical vertebrae in Armadillos; and the middle and poste- rior canals are the intervertebral foramina for the third and fourth cervical nerves. The upper and inner foramina and canals represent the remains of the primitive inter- spaces between the several arches. The anchylosed spinous processes, and the bodies of the three coalesced vertebrae, are completely broken away, so that nothing can be said regarding their characters. The fifth and sixth Cervical Vertebrae. — No remains of the fifth and sixth cervical ver- tebrae have been discovered among the bones sent by Sehor Terrero. The “ Trivertebral bone” or anchylosed seventh Cervical and first and second Dorsal Ver- tebrae (Plate VII. figs. 3, 4, 5, 6). — The three vertebrae which enter into the composition of this singular bone are very much depressed from above downwards, so that the neural canal is more than twice as wide as it is high ; while the greatest depth of the whole bone, leaving the spinous process out of consideration, is hardly a fourth of its width. The inferior face of the bone is deeply concave from side to side ; and as the floor of the neural canal is also concave, the part which corresponds with the centra of the anchylosed vertebrae has the form of a broad thin arched plate, thinnest in the middle. The supe- rior arches of the vertebrae, which constitute the roof of the trivertebral bone, follow, in a general way, the contour of its floor ; but they are much thicker ; and, posteriorly, the roof of the trivertebral bone is produced, upwards and backwards, into a very thick short process, which probably represents the spinous processes of the two anterior dorsal vertebrae. The lateral parts of the trivertebral bone, which represent the anchylosed transverse processes of the vertebrae, are very thick and stout, especially in front. Viewed from above, or laterally, they are seen to be marked out by excavations into three portions, one for each primitive vertebral constituent of the bone. With the lateral excavations the heads of the two anterior ribs articulate. So much for the general characters of this bone. A front view (Plate VII. fig. 5) exhibits the following features, worthy of more particular description. The lateral mass, which represents the transverse process of the first of the three vertebrae, presents an elongated oval articular facet (a), convex from above downwards and looking almost 62 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. directly forwards, its long axis being horizontal and at right angles to the axis of the spinal canal. The facet is 1*8 inch long by 09 inch maximum height. This articular facet is separated by a deep groove, into the bottom of which a large canal ( d ) opens, from two other articular surfaces (b, c ), placed one immediately above the other, and also parted by a deep channel, which may be regarded as an internal branch of the groove. The lower articular face (c), almost flat, looks inwards and forwards ; and its long axis, which continues the direction of the floor of the neural canal, is inclined from above downwards and outwards. The upper facet (b), also flat, and, elongated transversely, looks directly upwards. Its inner end is nearer the lower facet than its outer end ; and a well-marked fossa or depression lies behind it. The upper articular surface certainly answers to the anterior oblique process or “ prezygapophysis ” of the seventh cervical vertebra. The nature of the lower and of the outer facet will only become obvious when the characters of the cervical vertebrae of recent Armadillos have been explained. The anterior face of the spinous process of the trivertebral bone exhibits two ridges, each convex towards the middle line, which divide the face into a middle and two lateral areae. The upper face of the bone (Plate VII. fig. 3) presents three pairs of foramina, termi- nating internally in canals which lead into the spinal canal, and externally opening into recurved grooves on the surface of the bone. The middle apertures are the largest, and the corresponding grooves more strongly defined and wider. The posterior apertures are smallest, and are situated quite close to the hinder margin. The surface of the bone between these apertures is rough and irregular. The margins of this face of the bone are produced into three processes which alternate with the foramina. The hindermost of these processes is the largest, and ends in a point which is somewhat recurved and bent down. A side view of the trivertebral bone (Plate VII. fig. 6) shows that these processes are continued into irregular vertical ridges, between which two fossae are enclosed. Of these, the anterior is much deeper and more capacious than the other. It is an irre- gular cavity subdivided by a vertical ridge into two, each of which presents a somewhat deeper fossa at its inner and lower end. The second, shallower, fossa, which lies between the hinder face of the middle process and the front face of the posterior process, presents an elongated irregular articular facet on its anterior wall, and a more rounded articular surface on its posterior wall. The second rib is received into this fossa, and articulates with both these facets. The posterior face of the third process presents a small, slightly concave, oval arti- cular face on its lower half, with which the third rib was doubtless connected. The posterior aspect of the trivertebral bone (Plate VII. fig. 4) presents for notice, besides the features already mentioned, several others. The neural arch of the hindermost vertebra of the three overhangs ; and its under face exhibits two oval slightly concave articular faces (a, a), the posterior oblique, or “ postzygapophysial,” surfaces of the PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 63 second dorsal vertebra. These, however, are not carried upon distinct processes. The great spinous process seems completely to fill up the interval which properly exists between the postzygapophyses. The posterior face of this process is slightly excavated in the middle of its lower half. Its sides are also a little concave, so that the top swells out into a sort of knob with overhanging margins. The posterior part of the floor of the trivertebral bone is broken away ; but the hinder face of each lateral mass exhibits a transversely elongated articular surface ( b , b), concave from above downwards, so as to resemble a segment of a hollow cylinder, the axis of which is directed from within outwards and very slightly backwards. The inferior face of the trivertebral bone presents the arched surface, flatter behind than in front, of the continuously ossified central portions or bodies of the vertebrae, and, external to these, two pairs of apertures which perforate this face of the bone at its outer margin. The anterior of these apertures is very much larger than the poste- rior, and corresponds with the inner end of the middle transverse process, opening just behind the inner end of the first rib. Strictly speaking, the foramen seen upon the front face of the bone (Plate VII. fig. 5, d) forms one of this series of foramina (all of which are the terminations of short passages leading into the spinal canal) ; so that, as upon the upper, so on the under surface of the trivertebral bone, there are three pairs of foramina in communication with the spinal canal, and of these the middle pair are, in each series, the largest. The homologies of the three vertebrae which compose the trivertebral bone are deter- mined by the implantation of the head of the first rib into the great fossa between the lateral processes of the first and second. The vertebra which yields the anterior wall of the fossa is clearly the last cervical, and that which furnishes the posterior wall is the first dorsal. Plence the trivertebral bone is composed of the last, or seventh, cervical and the first and second dorsal vertebrae. The remaining Dorso-lumbar Vertebrae. — Of these vertebrae thirteen are preserved. The anterior twelve have plainly been immoveably united together into a continuous arched tunnel or tubular bridge of bone, partly by anchylosis and partly by the manner in which their apposed surfaces interlock (Plate VIII. figs. 1-7). The four anterior vertebrae (figs. 1, d. 1. 3, 4, 5, 6) are so completely anchylosed together that almost all traces of their original distinctness are lost. Persistent sutures, of a cha- racter intermediate between a “ harmonia ” and a serrated suture, separate the fourth vertebra (d. 1. 6) from the fifth, and the latter from the sixth ; but the sixth and the seventh ( d . 1. 9) are completely fused into one bone. Between the eighth and ninth vertebrae a suture is interposed, and also between the ninth and the tenth, at least on the left side. The tenth and the eleventh [d. 1. 13) are completely anchylosed above, while the suture seems to have persisted below *. * It is convenient to speak of the first, second, (fee. of the thirteen vertebrae which succeed the trivertebral bone ; but it must be recollected that the first of these is the third of the dorso-lumbar series, the second the fourth dorso-lumbar, and so on, the number of any one of these vertebrae in the dorso-lumbar series being MDCCCLXV. L 64 PROFESSOR HIJXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. Thus far, no trace of distinct articular processes is visible upon these vertebra ; but the hinder face of the eleventh vertebra ( d . 1. 13) presents certain irregular elevations and depressions, which interlock with corresponding ridges and cavities of the anterior face of the twelfth vertebra. The hinder face of the twelfth (d. 1. 14) and the front face of the thirteenth vertebra ( d . 1. 15) are in like case. I shall return to the con- sideration of the character of these irregular articular elevations and depressions after describing the general form of the vertebrae. In all but the first, second, third, eleventh, and thirteenth vertebrae, the parts repre- senting the vertebral centra are broken away, but, when they remain, they are so similar to one another that their form was, doubtless, essentially the same throughout. Each centrum is a comparatively thin bony plate, bent so as to be convex downwards and concave upwards, and presenting a much flatter curve in the anterior than in the poste- rior part of the column. In front, the central plate is not more than OT inch thick in the middle, but it becomes thicker posteriorly, so that the centrum of the eleventh vertebra is 045 inch thick; that of the thirteenth vertebra is OT inch thinner. At the sides and above, the curved central part of the vertebra passes into the lateral pro- cesses and upper arches, which last are slightly concave downwards in the first vertebra, flat in the middle vertebrae, and somewhat arched again in the thirteenth. The contour of a transverse section of the spinal canal is a transversely elongated oval in the first vertebra (fig. 3), is more nearly round, but flattened at the top, in the middle vertebrae (d.l. 12), and is a vertically elongated oval in the thirteenth vertebra (d. 1. 15). The spinous and transverse processes of the vertebrae are represented by three crests or ridges of bone. One of these (Plate VIII. fig. 2, a , b), vertical, and situated in the middle line of the dorsal surfaces of the arches of the vertebrae, represents the spinous processes; while the lateral crests (<?,<?), directed obliquely upward and downwards, answer to transverse, accessory, and mammillary processes. As the latter ridges become directed more upwards towards the hinder part of the dorsal region, the total width of the column lessens, and the grooves between the middle and the outer ridges become deeper in the same direction. Thus, anteriorly, the column is fully six inches broad, while at the eleventh vertebra the distance from one external ridge to another is hardly half this amount. The first vertebra (d. 1. 3) is as broad and depressed as the trivertebral bone. Viewed in front (Plate VIII. fig. 3), the neural canal is seen not to take up more than one-fourth of the face of the bone, the rest of which is occupied by two broad expanded transverse processes, directed very slightly upwards as well as outwards. The under half of each of these processes presents an elongated articular facet (a, a'), convex from above downwards, slightly concave from side to side, which corresponds with, and is received into, the concave articular surfaces upon the hinder face of the trivertebral bone. always greater by two than its number reckoned as one of tbe thirteen. In order to avoid confusion in describing each vertebra, I shall occasionally give after it its number in the dorsal lumbar series, e. g. (d. 1. 3), (d. 1. 6), by which it is indicated in the figures. PEOFESSOE HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 65 Seated upon the upper face of the neural arch are two other oval articular surfaces (b, b'), which answer to the postzygapophysial surfaces upon the under surfaces of the hinder part of the neural arch of the trivertebral bone. The inner part of each of these articular faces is convex in all directions ; the outer is concave from side to side, convex from before backwards ; behind each lies a transverse fossa. The outer ends of the transverse processes are obliquely truncated, and each presents two articular facets, an anterior and inferior, larger, and a posterior and superior smaller, which articulate with corresponding facets upon the capitulum and tuberculum of the attached rib. A well-marked notch separates the hinder face of the transverse process of the first from that of the second vertebra ; and the intervertebral foramen is situated on the same level as this notch, on the one hand, and the anterior inferior facet, on the other, or about halfway between the upper and lower faces of the bone. The transverse process of the second vertebra ( d . 1. 4) presents two oval articular facets for the head of a rib, more nearly equal and more nearly on a level than those of the first vertebra. The transverse process of the third vertebra is broken on the left side ; but on the right side, traces of an elongated costal facet are visible. The ends of the lateral ridges representing the transverse processes of the fourth, fifth, sixth, and seventh vertebrae are broken away. In the eighth, ninth, tenth, and eleventh vertebrae (Plate VIII. fig. 7, d. 1. 10, 11, 12) they are preserved on the left side, broken away on the right ; on the twelfth vertebra the corresponding ridges are broken on both sides. I find no trace of articular surfaces for ribs on the lateral ridge continued along the eighth, ninth, tenth, and eleventh vertebrae, which, as I have stated, is entire on the left side ; but the upper and inner surface of the ridge is rounded and marked by longi- tudinal striations (fig. 7). The outer surface is rough and irregular, opposite the ante- rior part of each vertebra, and raised into an irregular tubercle posteriorly. The spinous processes of all the vertebrae are broken short off; that of the first is almost obsolete, being a mere ridge sloping back towards the second, into which it is continued. The anterior edge of the process is so much inclined backwards and upwards as to afford free play to the knobbed head of the spinous process of the triver- tebral bone (fig. 2). The spinous process of the second vertebra ( d . 1. 4) is 04 inch thick where it is broken through, and had probably a considerable height. A distinct interval separates it posteriorly from the thin anterior edge of the spinous process of the third vertebra, which is much thinner, and is anchylosed with its successors, as far as the eleventh inclu- sive, into a long continuous crest ; slight traces of the original separation of the several spinous processes, however, are visible at the base of the crest, and they may have been distinct at their apices. The crest gradually increases in thickness to the sixth vertebra (d. 1. 8) (where it attains 0*75 inch), and then gradually diminishes. The spinous process of the twelfth vertebra (d. 1. 14) may have been distinct down to its L 2 66 PEOFESSOE HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. base ; and the posterior edge of the thin ridge, which is all that is left of the process, appears to incline upwards and forwards. The foramina for the exit of the spinal nerves are not intervertebral in the ten anterior vertebras, but perforate the bony substance of each vertebra nearer its posterior than its anterior boundary. Of these foramina there are two, on each side, for the five anterior vertebrae ; one, larger, below the lateral apophysial ridge ; and one, smaller, above, or upon, this ridge at the posterior boundary of each vertebra. The larger foramen approaches the outer margin of the apophysial ridge, or seems to be situated higher up, in each successive vertebra from the first to the seventh. Beyond this point the level of the foramen descends somewhat. The eleventh vertebra ( d . 1. 13) appears to have possessed a simple intervertebral notch posteriorly, on the left side ; but, on the right, a bar of bone is preserved, separating an anterior foramen from the rest of the notch, which receives a process of the twelfth vertebra. The arrangement appears to be the same in the twelfth vertebra ( d . 1. 14) ; that is to say, the apparent notch has been divided by a bar of bone into an anterior nervous foramen, and a posterior articular fossa. I have briefly referred, above, to the articular surfaces of the eleventh and twelfth vertebrae, which are exceedingly irregular and distorted, apparently from partial anchy- losis and filling up with osseous matter. A notion of their general character may best be obtained by the study of the posterior face of the twelfth vertebra ( d . 1. 14). On the upper part of the neural arch, on each side of the spine of this vertebra, irregular and partially obliterated posterior oblique processes, or postzygapophyses, are discern*- ible. The zygapophysis is separated by a depression, or groove, directed from without obliquely downwards and inwards, from a wedge of bone which terminates the apophy- sial ridge. Inferiorly and externally, this wedge presents a slightly concave articular facet, separated by a deep fossa from a tuberosity with a rounded surface, which passes down into the body of the vertebra. On the same level as this fossa, there projects from the front surface of the vertebra a triangular process, which fits into a corresponding fossa of the eleventh vertebra. The front face of the thirteenth vertebra ( d . 1. 15), again, presents, on each side of the neural spine, pits, the floors of which answer to the anterior oblique processes, or prezygapophyses; outside of these are ridges, which fit into the fossae between the postzygapophysis of the twelfth vertebra and the wedge-shaped process ; external to the ridges are fossae which receive those wedge-shaped processes ; and exter- nal to and below these, again, are the remains of processes which were received into the deep fossae mentioned above. Except in the region of these articular processes, neither the anterior nor the poste- rior ends of the thirteenth vertebra (Plate VIII. figs. 6 & 7, d l. 15) are entire. Of the spinous process, only the base is left ; it thins off anteriorly to a natural edge, which is inclined upwards and backwards, and seems to have been quite free. Posteriorly, it becomes rapidly thicker ; but its mode of termination cannot be ascertained. The large nervous foramen perforates the wall of the vertebra, on a level with the articular pro- PROFESSOR HUXLEY OX THE OSTEOLOGY OE THE GENUS GLYPTODON. 67 cesses, and bifurcates externally, so that one of its apertures ends above, and the other below, a stout bar of bone (Plate VIII. fig. 6, a), nearly an inch thick, which ends poste- riorly in a raised curved ridge, forming the anterior boundary of a semicircular groove. The spinal canal in the thirteenth vertebra is, as I have said, oval in shape, the long diameter of the oval (T5 inch in length) being vertical, the short diameter (IT inch) transverse. As, in the anterior part of the lumbo-sacral region, this canal has a very different shape, it is probable that two or three vertebrae are wanting in this portion of the spinal column. The Sacrum and Coccygeal Vertebrae. — The “ sacrum,” composed of anchylosed lumbar, proper sacral, and coccygeal vertebrae, contains at fewest twelve, and perhaps thirteen vertebrae. The centra of the two hindermost lumbar vertebrae and of the two proper sacral vertebrae, which follow them (Plate IX. fig. 2), are thin and broad bony plates, flat above, and slightly concave from side to side below, exhibiting a most marked con- trast to the semicylindrical form of the same part in the hindermost of the thirteen vertebrae described above. The plane of the plate formed by the centra of the anchy- losed lumbar vertebrae is inclined, upwards and forwards, to pass into the general curve of the dorso-lumbar region. The plane of the centra of the two succeeding sacral ver- tebrae, on the other hand, is horizontal ; and it is obvious, from the characters of the rest of the sacrum, that the centra of the following vertebrae, to the end of the sacral region, were arranged in an almost semicircular curve, the chord of which is about 18 inches long (Plate IX. fig. 3). The posterior face of the hindermost coccygeal vertebra (Plate IX. fig. 1, a) is broad, oval, and very slightly concave, like the face of an ordi- nary vertebral centrum ; but the centrum of the penultimate coccygeal vertebra is much flatter and narrower; and this flattening and narrowing become still more marked in the centrum of the antepenultimate vertebra and of that which precedes it, or the fourth from the end. From this point to the two anterior sacral vertebrae the floor of the sacral canal is completely broken away, but there can be little doubt that the missing centra were represented by a broad and flat bony plate. The neural arches are but imperfectly preserved, except in the lumbar region and the anterior part of the sacrum. They are thin, and are separated by large intervertebral foramina. In the lumbar vertebrae these foramina pass downwards and backwards into grooves which mark the sides of the central plate. Well-defined depressions upon the sides of the sacral crest lead upwards and backwards to the canals which pass between that crest and the ilia. The four last coccygeal intervertebral foramina are still larger, and indicate the passage of large nerves to the muscles moving the tail. The spinous processes of all the vertebrae which enter into the sacrum, up to the fourth from the end inclusively, are anchylosed together into a long and strong osseous crest (Plate IX. figs. 3 & 4), which expands above, so as to present a broad and very rugged superior face. This crest is 8 inches high in front, but slowly diminishes as it follows 68 PROFESSOR HTJXLET OX THE OSTEOLOGY OE THE GENUS GLYPTODON. the curve of the centra posteriorly, to 5 inches. The spinous process of the penultimate coccygeal vertebra is very thick, but it is broken short off. It was probably not less than 4 inches high, and afforded a middle point of support for the dermal shield between the ischial protuberances (Plate IX. fig. 1). The sides of the two anterior sacral vertebrae and the corresponding part of the sacral crest are anchylosed with the inner edges of the iliac bones, so that only a narrow oval space, left between these parts, near the upper edge of the crest, and the small canals above mentioned, allow of any communication between the region in front of, and that behind the ilia. Behind this point the vertebrae are devoid of transverse processes as far as the fourth from the end. But the antepenultimate had a long and slender transverse process on each side ; the penultimate possesses an equally long but much stouter process, and the last coccygeal vertebra has extremely thick processes of the same length. The enlarged distal ends of these processes unite with one another and with the inner surfaces of the ischia (Plate IX. figs. 1, 2, 4). Caudal Vertebra. — No caudal vertebrae existed among the remains of this specimen of Glyptodon. Of the Vertebral Column as a whole. — It appears from the foregoing description that the atlas of the Glyptodon was moveable upon the odontoid vertebra ; but that the latter was anchylosed with the third and fourth cervical vertebrae into one short bone, move- able upon the fifth cervical ; of the fifth and sixth cervical vertebrae no remains exist. The seventh cervical is anchylosed with the first and second dorsal into a single “ triver- tebral bone,” upon the front part of which the sixth cervical was certainly moveable ; while the hinder part of it freely articulates with the third dorsal, so that the bone was capable of motion through a certain vertical arc. Beyond this point, as far as the fourteenth dorso-lumbar vertebra, the vertebrae are so connected by complete, or partial, anchylosis, that it is impossible any motion should have taken place between them ; and it is probable, though not so certain, that the fifteenth dorso-lumbar vertebra was similarly fixed. Between this and the two hindermost lumbar vertebrae, which are completely anchy- losed together and with the sacral vertebrae, there is a hiatus, but the condition of the two latter is not such as to lead to the supposition that the intermediate vertebrae were less firmly united than they. The free cervical portion of the vertebral column must have been remarkably short, probably not exceeding 8 inches in length, and the cervical vertebrae were most likely arranged in a nearly straight line. The trivertebral bone and the thirteen following dorso-lumbar vertebrae, when articu- lated together, form one great curve, concave downwards or towards the visceral cavity, the curve being much sharper in the anterior than in the posterior part of the column. Measured along its curvature, this part of the vertebral column is about 35 inches long. At the anterior part of the sacral region the lumbar curve passes into the straight PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 69 line of the two anterior sacral vertebree, behind which commences the great sacro- coccygeal curve, concave towards the cavity of the pelvis. The lumbo-sacral is very nearly as long as the dorso-lumbar region, so that the vertebral column, from the last cervical to the last coccygeal, may be said to form two subequal arches with a common pier, formed by the proper sacral vertebrae. Description of the Plates. PLATE IV. Figs. 1 & 3. Upper and under views of the skull of the “new specimen” of Glyptodon clavipes. Figs. 2, 4, & 5. Upper, under, and side views of the hinder part of the skull of the “typical specimen” of Glyptodon clavipes. All reduced to one-half the natural size. PLATE V. Fig. 1. Side view of the skull of the new specimen of Glyptodon clavipes. Fig. 2. The left half of the mandible of the same, one-half the natural size. Fig. 2°. The ascending ramus of the mandible, viewed from behind. Figs. 3 & 4. Grinding-surfaces of the teeth, of the natural size. PLATE VI. Front view, and Back view of the skull of the new specimen of Glyptodon clavipes. View of the occipital face of the skull of the typical specimen. Front view, and Upper view of the mandible of the new specimen. All reduced to one-half the natural size. PLATE VII. Figs. 1 & 2. Front and back views of the fragment of the atlas. *** The artist has inadvertently inverted each figure, so that the lower side of the bone is turned upwards, and vice versa. Fig. 3. The trivertebral bone, seen from above. Fig. 4. The trivertebral bone, from behind ; d, the first rib, in place. Fig. 5. The trivertebral bone, from in front. Fig. 6. The trivertebral bone, viewed from the right side. Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. 70 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. Fig. 7. The fragment of the first rib of the right side, viewed from without. Figs. 8, 9, 10. Front, inner, and outer views of the fragment of the third left rib. PLATE VIII. Fig. 1. The third to the ninth dorso-lumbar vertebrae, viewed laterally. Fig. 2. The same, viewed from above. Fig. 3. The anterior face of the third dorso-lumbar vertebra. Fig. 4. The posterior face of the sixth dorso-lumbar vertebra. Fig. 5. The anterior face of the twelfth and thirteenth dorso-lumbar vertebrae. It is much mutilated, especially below and on the left side, none of the centrum of the twelfth vertebra remaining. Fig. 6. The tenth to the fifteenth dorso-lumbar vertebrae, viewed laterally. Fig. 7. The same, from above. All reduced to one-half the natural size. PLATE IX. Back view of the pelvis of Glyptodon clavipes. Front view of the same. Side view of the same. Upper view of the same. All these figures are reduced to one-sixth the natural size. -8. Outer, inner, back and under views of the fragment pf the anchylosed odontoid, third, and fourth cervical vertebrae, one-half the natural size. a the upper, and b the lower end of the bone in each figure, which is reduced to one-half the natural size. Fig. 1. Fig. 2. Fig. 3. Fig. 4. Figs. 5- Bub. Trans. MD C CGLXV Biota IV". f BO ,di pEbdeben. daL feifli. "W/West imp. Tkil/. 2WMDCCGLXV. FlaXa V. J-Erxlebeii dsL W.'West imp. Phl.TrcLOS.y~MZlJiy. TlateVl .Pluls. 'Trans. MDCGCLXV. Exrtb YII. J.Eiieben. del. .felifli. T/Ofest ingo. BdL.Tnms. MD CGCW. P1.YII1 A L. 11. eLl.11. Al.15. ■A l. 13. Pig. 7. "VTOfestimp. J.EcxLeben- deL JPkiL.Trans. MD CCCLXY. Flabb IX. "W.West imp. J.Endeben. del &]ifh.. 1 71 ] * III. Investigations of the Specific Heat of Solid Bodies. By Hermann Kopp. Communicated by T. Graham, Esq., F.B.S. Received April 16, — Read May 12, 1864. I. Historical Introduction. I. About the year 1780 it was distinctly proved that the same weights of different bodies require unequal quantities of heat to raise them through the same temperature, or on cooling through the same number of thermometric degrees, give out unequal quan- tities of heat. It was recognized that for different bodies the unequal quantities of heat, by which the same weights of different bodies are heated through the same range, must be determined as special constants, and considered as characteristic of the individual bodies. This newly discovered property of bodies Wilke designated as their specific beat , while Crawford described it as the comparative heat, or as the capacity of bodies for beat. I will not enter upon the earliest investigations of Black, Irvine, Crawford, and Wilke, with reference to which it may merely be mentioned that they depend essentially on the thermal action produced when bodies of different tem- peratures are mixed, and that Irvine appears to have been the first to state definitely and correctly in what manner this thermal action (that is, the temperature resulting from the mixture) depends on the original temperature, the weights, and the specific heats of the bodies used for the mixture. Lavoisier and Laplace soon introduced the use of the ice-calorimeter as a method for determining the specific heat of bodies ; and J. T. Mater showed subsequently that this determination can be based on the observa- tion of the times in which different bodies placed under comparable conditions cool to the same extent by radiation. The knowledge of the specific heats of solid and liquid bodies gained during the last century, and in the first sixteen years of the present one, by these various methods, may be left unmentioned. The individual determinations then made were not so accurate that they could be compared with the present ones, nor was any general conclusion drawn in reference to the specific heats of the various bodies. 2. Dulong and Petit’s investigations, the publication of which commenced in 1818, brought into the field more accurate determinations, and a general law. The investiga- tions of the relations between the specific heats of the elements and their atomic weights date from this time, and were afterwards followed by similar investigations into the rela- tions of the specific heats of compound bodies to their composition. In order to give a general view of the results of these investigations, it is desirable to present, for the ele- ments mentioned in the sequel, a synopsis of the atomic weights assumed at different MDCCCLXV. M 72 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. times, and of certain numbers which, stand in the closest connexion with these atomic weights. Berzelius’s atomic weights. Regnault’s thermal atomic weights. Usual equivalent weights. Modem atomic weights. Aluminium A1 = 13-7 A1 = 13-7 A1 = 13-7 A1 = 27-4 Antimony Sb = 61 Sb = 61 Sb =122 Sb =122 Arsenic As = 37-5 As = 37-5 As = 75 As = 75 Barium Ba = 68-5 Ba = 68-5 Ba = 68-5 Ba =137 Bismuth Bi =105 Bi =105 Bi =210 Bi =210 Boron B = 10-9 B = 10-9 B = 10-9 B = 10-9 Bromine Br = 40 Br = 40 Br = 80 Br = 80 Cadmium Cd = 56 Cd = 56 Cd = 56 Cd =112 Calcium Ca = 20 Ca = 20 Ca = 20 Ca = 40 Carbon C = 6 C = 12 C = 6 C = 12 Chlorine Cl = 17-75 Cl = 17-75 Cl = 35-5 Cl = 35-5 Chromium Cr = 26-1 Cr = 26-1 Cr = 26-1 Cr = 52-2 Cobalt Co = 29-4 Co = 29-4 Co = 29-4 Co = 58-8 Copper Cu = 31-7 Cu = 31-7 Cu = 31-7 Cu = 63-4 Fluorine FI = 9-5 FI = 9-5 FI = 19 FI = 19 Gold Au = 98-5 Au = 98-5 Au =197 Au = 197 Hydrogen H = 0-5 H = 1 H = 1 Iodine I = 63-5 I = 63-5 I =127 I =127 Iridium Ir = 99 Ir = 99 Ir = 99 It =198 Iron Fe = 28 Fe = 28 Fe = 28 Fe = 56 Lead Pb =103-5 Pb =103-5 Pb =103-5 Pb =207 Lithium Li = 7 Li = 3-5 Li = 7 Li = 7 Magnesium Mg= 12 Mg= 12 Mg= 12 Mg= 24 Manganese Mn= 27-5 Mn= 27-5 Mn= 27-5 Mn= 55 Mercury Hg =100 Hg = 100 Hg = 100 Hg=200 Molybdenum Mo= 48 Mo = 48 Mo= 48 Mo= 96 Nickel Ni = 29-4 Ni = 29-4 Ni = 29-4 Ni = 58-8 Nitrogen N = 7 N = 7 N = 14 N = 14 Osmium Os = 99-6 Os = 99-6 Os = 99-6 ©s =199-2 Oxygen 0=8 0=8 © = 16 Palladium Pd = 53-3 Pd = 53-3 Pd = 53-3 Pd =106-6 Phosphorus P = 15-5 P = 15-5 P = 31 P = 31 Platinum Pt = 98-7 Pt = 98-7 Pt = 98-7 Pt =197-4 Potassium K = 39-1 K = 19-55 X = 39-1 K = 39-1 Rhodium Rh= 52-2 Rh= 52-2 Rh = 52-2 Rh =104-4 Rubidium Rb= 85-4 Rb= 85-4 Rb= 85-4 Selenium Se = 39-7 Se = 39-7 Se = 39-7 Se = 79-4 Silicium Si = 21 Si = 14 Si = 28 Silver Ag = 108 Ag = 54 Ag =108 Ag =108 Sodium Na= 23 Na = 11-5 Na = 23 Na = 23 Strontium Sr = 43-8 Sr = 43-8 Sr = 43-8 Sr = 87-6 Sulphur S = 16 S = 16 S = 16 S = 32 Tellurium Te = 64 Te = 64 Te = 64 Te =128 Thallium T1 =204 Tl =102 Tl =204 Tl =204 Tin Sn = 59 Sn = 59 Sn = 59 Sn =118 Titanium Ti = 25 Ti = 25 Ti = 25 Ti = 50 Tungsten W = 92 W = 92 W = 92 W =184 Zinc Zn = 32-6 Zn = 32-6 Zn = 32-6 Zn = 65-2 Zirconium Zr = 33-6 Zr = 44-8 Zr = 89-6 For each of the previous columns the relation of the numbers to each other is alone important, and not the number which is taken as unit or starting-point. Berzelius’s atomic weights and Regnault’s thermal atomic weights are corrected with the nearest PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 73 and most trustworthy experimental determinations, without alteration of the bases for the adoption of these numbers. The numerical relations presented in the above Table require, from the chemical point of view, no further explanation. The relations of these numbers to the specific heat form the subject of the investigations which are presented in the sequel. 3. The experiments by which Dulong and Petit * * * § showed, in the case of mercury various solid metals, and glass, that the specific heat increases with increasing tem- perature, were made by the method of mixtures. They determined at ordinary tem- peratures the specific heats of a greater number of elements by the method of cooling f. They found that when the numbers in the first column in § 2 corresponding to the elements Bi, Pb, Au, Pt, Sn, Zn, Cu, Ni, Fe, and S (the Berzelian atomic weights) are multiplied by the respective specific heats of these bodies, approximately the same number is obtained ; and that approximately the same number is also obtained when Ag, \ Te, and f Co are multiplied by their corresponding specific heats. They were of opinion that the atomic weights of the elements could and should be so selected that, when multiplied by the specific heats, they should give approximately the same number as product. This observation and this view, which Dulong and Petit stated in 1819 in the following manner, “The atoms of all simple bodies have all exactly the same capacity for heat,” have since that time been known as Dulong and Petit’s Law. I shall not here dwell upon Potter’s investigations on the specific heat of metals and on the validity of Dulong and Petit’s lawj, but proceed directly to discuss Neumann’s investigations, which rank worthily by the side of those of Dulong and Petit. 4. In his “Investigation on the specific heat of Minerals,” Neumann (in 1831) first published § more accurate determinations of the specific heats of solid compounds. He investigated a large numbfer of such compounds, especially those occurring in nature, partly by the method of mixture, and partly by the method of cooling ; and he deter- mined the sources of error in both these methods, and the corrections necessary to be introduced. In a postscript to this paper, he mentioned that he continued the investi- gations with an apparatus which, compared with that he had previously used, promised far greater accuracy in the individual results, without needing tedious and troublesome reductions. This apparatus, by means of which the specific heats of solid bodies, which may be heated in a closed space surrounded by steam, can be determined with great accuracy, he has not described ||. Of the general results of Neumann’s investigations, one must be particularly men- * Annales de Chimie et de Physique, [2] vol. vii. p. 142. + Ibid. vol. x. p. 395. + Edinburgh Journal of Science, New Series, vol. v. p. 75, and vol. vi. p. 166. J. F. W. Johnston’s remarks, vol. v. p. 278. I only know these papers from Berzelius’s e Jahresbericht,’ vol. xii. p. 17, and Gehxer’s ‘ Physicalisches Worterbuch,’ new edition, vol. x. part 1, p. 805 et seq. § Poggendorff’s ‘Annalen,’ vol. xxiii. p. 1. || Pape (Poggendorff’s ‘ Annalen,’ vol. cxx. p. 337) has recently described this apparatus. I have had no M 2 74 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. tioned, that a dimorphous substance has the same specific heat in its two conditions. This he showed was the case with arragonite and calcite, and with iron pyrites and marcasite. But the most important is the discovery that in analogous compounds the products of the atomic weights into the specific heats are approximately equal. Neu- mann stated this last observation in the following manner : — “ In bodies of analogous chemical composition the specific heats are inversely as the stochiometrical quantities, or, what is the same, stochiometrical quantities of bodies of analogous chemical com- position have the same specific capacity for heat.” Neumann adduced 8 carbonates, 4 sulphates, 4 sulphides (Me S), 5 oxides (Me O), and 3 oxides (Me203), as showing this regularity, which is to be denoted as Neumann’s law *. 5. Soon after the publication of Neumann’s researches in 1833, Avogadro published f a “ Memoir on the Specific Heat of Solid and Liquid Bodies.” He there gave a number of determinations of the specific heat of solid bodies made by the method of mixture. As far as can he ascertained by comparison with the most trustworthy of our newer de- terminations, these results are by no means so accurate as those of Neumann; but they are far more accurate than those which had been obtained up to about 1830, and many of them come very close to the best of our modern results. It would be unjust to Avogadro’s determinations $ to judge them all by one case, in which he obtained a totally erroneous result (for ice, by a modified method) ; and by the circumstance that in a subsequent memoir § he gives specific heats for several elements as deduced from his experiments, which are decidedly incorrect ||. Avogadro recognizes the validity of Hulong and Petit’s law. With reference to the specific heats of compound bodies, he considers that he had established, with tolerable probability, that for solid and liquid bodies the same regularity prevails which he had previously deduced for gases from Dulong’s experiments. That is, “ that the specific heat of the atom of a compound body is equal to the square root of the integral or fractional number expressing the atoms or parts of atoms which go to form the atom of the compound body such as it exists in the solid or liquid state, taking as unity the specific heat of the atom of a simple body in the samestate.” He observes that there is a difficulty incidental to the application of this law to solid and liquid bodies, which is not met with in the case of gaseous bodies, in which the composition by atoms or by volumes is held to be directly given by opportunity of seeing Neumann’s memoir cited by Pape, “ Commentatio de emendenda formula per quam calores corporum specifici ex experimentis metbodo mixtionis institutis computantur.” Regiomonti, 1834. * The objections of Regnault (Ann. de Chim. et de Phys. [3] vol. i. p. 131) as to the inadequacy of the proofs adduced 'by Neumann in support of the law do not apply. t Ann. de Chim. et de Phys. [2] vol. lv. p. 80, as an abstract from * Memorie della Societa Italiana delle Scienze residente in Modena,’ t. xx. Fascicolo 2 di fisica’. + They are also found in Gmexin’s ‘ Handbuch der Chemie,’ 4 Auflage, vol. i. in the Tables, pp. 215-218 et seq. § Ann. de Chim. et de Phys. [2] vol. lvii. p. 113. || I only know Avogadro’s investigations from the abstracts published in the Ann. de Chim. et de Thys., and am not aware whether the hold corrections of Avogadro urged by Regnault (Ann, de Chim. et de Phys. [2] vol. lxxiii. p. 10) were used in all his experiments, or only in some. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 75 observation. This difficulty consists in knowing what constitution is to be assigned to the body in question for the solid or liquid condition ; this constitution, from the conclusions derived from his theoretical considerations, would often be different from that which the body has in the state of gas or vapour. His considerations led him to assume the atomic weights of many elements different from those which Berzelius had given : Avogadro described the atoms, to which the weights assumed by him refer, as thermal atoms. 6. B. Hermann published in 1834 a memoir “ On the Proportions in which Heat unites with the Chemical Elements and their Compounds, and on the Combining Weights considered as quotients of the capacity for Heat of Bodies into their Specific Gravities”* * * §. He gives there a great number of determinations of the specific heat of solid bodies (of a few elements, but chiefly of compound bodies). He made a few ex- periments in which he used Lavoisier and Laplace’s calorimeter f ; but by far the greater number of determinations are made by the method of cooling Many of his results approach very closely to those which are at present considered accurate, but they are in so far untrustworthy that a considerable number among them are decidedly incorrect. As for Hermann’s theoretical results, it must be borne in mind that, regarding matter as he does, not from the point of view of the atomic but of the dynamical theory, he puts the idea of combination weights in the place of the idea of atomic weights. The propositions which he endeavours to establish are the following. The quotients obtained by dividing the specific gravities cf the elements § in the solid state by their specific gravities in the gaseous state, are either equal or stand to each other in simple ratios ; they are 1,2 15 times as much as a certain base. The same is the case with the products of the specific gravities of the solid elements into their specific heats, that is, with their relative heat ; and the number indicating the multiple for a given element is the same for both the above relations. It follows from this that the combining weights m of the elements are proportional to the quotients of their relative heats into their specific gravity in the solid condition ; that the products of the specific heats and the combining weights for different elements are equal to a constant, and that from the known combining weight of an element its specific heat in the solid form may be calculated (it is equal to 0'3m7 5, where m is the combining weight of the substance in question referred to oxygen = 1). For several elements (phosphorus, * Nouveaux Memoires de la Societe Imperiale des Naturalistes de Moscou, vol. iii. p. 137. + Hermann tried to alter this apparatus so as to make it serve for measuring the change of volume which takes place when ice melts ; but he did not further follow this application of the modified apparatus. X They are found not quite complete in Gmelin’s £ Handbuch der Chemie,’ 4 Auflage, in the Tables, pp. 215-218 et seq. § Hermann considers that the specific gravities of the elements in the state of gas or vapour are either obtained by observation, or may be theoretically deduced by assuming that they are in the ratio of the com- bining weights. 76 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. tellurium, cadmium, and silver for instance) atomic weights are taken which differ from those of Berzelius. In the case of the sulphides, the specific heats may be calculated from those of the constituents, assuming that the specific heats of the elements in these compounds are the same as in the free state. The same holds good for several chlorides and for basic metallic oxides, if the specific heats of chlorine and of oxygen, as given by the above formula, are taken as basis. But in acids a smaller specific heat must be taken for oxygen (one half in several acids and null in phosphoric acid) ; and there are even compounds (cassiterite, e. g., or arsenious acid), in which the same element is contained partly with the normal and partly with the modified specific heat* * * §. For oxygen salts it is to be assumed that both the acid and the base have the same specific heat as in the free state, and hence the specific heat of one constituent (of the acid, for instance) may be calculated, if that of the salt and that of the other constituent (the base) is known ; and it is also found that the specific heat of chromic acid in the neu- tral and in acid chromate of lead is the same. This memoir of Hermann’s did not become much known. Unacquainted with it, other philosophers have subsequently developed independently similar opinions. 7. In 1835 Rudberg described a method j*, which, by ascertaining the heat developed when salts are dissolved in water, in experiments in which the proportion of the salt to the water was constant, but the temperature of the salt varied, should give a means of at once determining the specific heat of the salt, and of the heat which was either absorbed or became free. Yet the numbers which he obtained from his experiments for the specific heat of solid salts are undoubtedly erroneous. Dumas $ (in 1838) discussed the possibility of determining the specific heat of organic bodies by the following process. A platinum vessel containing the substance in ques- tion, along with a thermometer, is to be heated to 30° or 40°, and then brought into a vessel provided with a second thermometer, and containing water, the temperature being about 5° or 6° lower than that of the surrounding room. When the temperature has risen to the same extent above that of the room, both thermometers are to be observed. I know no determinations made by this method. 8. In 1840 Regnault commenced the publication of a series of important investiga- tions on specific heat which he had made. As they are generally known, I may be more brief in enumerating the contents of the individual publications. In the first which he published, Regnault developed § the reasons which led him to prefer the method of mixture to other processes for determining the specific heats of solid bodies ; * Hermann designates such compounds as hermaphrodites. He thinks that an acid and a base may have the same composition, and that they may form salts with each other. Cassiterite, for instance, he considers to be stannate of binoxide of tin. f Berzelius’s ‘ Jahresbericht,’ vol. xv. p. 63. Poggendorff’s ‘Annalen’, vol. xxxv. p. 474. J Dumas’s “ These sur la question de Faction du calorique sur les corps organiques” (Paris, 1838) Ann. der Pharm. und Chem. vol. xxviii. p. 151. § Ann. de Chim. et de Phys. [2] vol. lxxiii. p. 5. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 7T he described his mode of executing this method, and published the results obtained for a great number of elements. In a second memoir * he gave the specific heats of several metallic alloys containing metals in simple atomic ratios, and of a great number of solid chemical compounds ; and he published comprehensive experiments on the specific heat of carbon in its different conditions. The investigations announced in the first memoir f on the specific heat of organic compounds, as well as those promised in the second memoir^ on the specific heat of sulphur at different temperatures, have not to my knowledge been published. But in a third memoir § Regnault has investigated the difference in the specific heats of certain metals according as they are hardened or soft, and also with reference to sulphur according as it is in the native crystallized form, or has solidified a longer or shorter time after being melted ; and he has more especially tried to impart greater certainty to the method of cooling. In his subsequent inves- tigations, however, he has only used the method of mixture as being the more certain. These investigations || have given the specific heats of a large number of solid elements, and also of individual compounds. By his investigations Regnault has removed some objections which seemed to affect Dulong and Petit’s law, and has given a great number of new cases in which it applies. He considers <|[ this law to be universally valid, and discusses the reasons why for individual elements the specific heats found do not quite agree with the law, but only approximately. In his view the atomic weight of an element is to be so taken that it agrees with Dulong and Petit’s law. He took the atomic weight of silver and of the alkaline metals half as great, and that of carbon twice as great as Berzelius had done. Yet with regard to selecting, by means of the specific heat, from among the numbers which the chemical investigations of an element has given as admissible, that which is the correct one, Regnault does not always express himself decidedly. In the case of carbon ** and of silicium f f he mentions the possibility of their disagree- ment with Dulong and Petit’s law. He proved the validity of Neumann’s law for a number of cases very considerably greater than that on which it had originally been based ; and he expressed it in a much more general form JJ. “ In all compounds of ana- logous atomic composition, and similar chemical constitution, the specific heats are approximately inversely proportional to the atomic weights. Regnault designates the numbers agreeing with this law as thermal atomic weights. He has either determined them directly from the numbers found for the specific heats of the elements in the free * Ann de Chim. et de Pkys. [3] vol. i. p. 129. + Ibid. [2] vol. lxxiii. p. 71. t Ibid. [3] vol. i. p. 205. § Ibid. [3] vol. ix. p. 322. || Ibid. [3] vol. xxvi. pp. 261 & 268 ; vol. xxxviii. p. 129 ; vol. xlvi. p. 257 ; vol. lxiii. p. 5. Comptes Rendus, vol. Iv. p. 887. i^[ Ann. de Cbim. et de Phys. [2] vol. lxxiii. p. 66 ; further, [3] vol. xxvi. p. 261, and vol. xlvi. p. 257. ** Ibid. [3] vol. i. p. 205. But botb before and after (Ibid. [2] vol. lxxiii. p. 71, and [3] vol. xxvi. p. 263) Regnault inclined to tbe view that carbon, with the equivalent= 12, and the specific heat found for wood-charcoal, must be considered as obeying Dulong and Petit’s law. ft Ibid. vol. lxiii. p. 30. Xt Ibid. vol. i. p. 199. 78 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. state, applying Dulong and Petit’s law, or indirectly by ascertaining the specific heat of solid compounds, assuming Neumann’s law ; or finally (and only in a few cases), he has determined them by means of their probable analogies. These are the atomic weights given in the second column of the Table in § 2. With regard to the relations of the specific heats of solid compounds to those of their constituents, Regnault has shown * that with metallic alloys, at a considerable distance from their melting-points, the specific heats may be calculated from those of their con- stituents in tolerable accordance with the experimental results, assuming that the specific heats of the metals are the same in the alloys as in the free state. The investi- gation, whether for true chemical compounds there is a simple relation between their specific heats and those of their constituent elements, Regnault has reserved *f* till the conclusion of his experiments on the specific heats of gaseous bodies $. To my know- ledge he has published nothing for solid bodies. But in 1862, with reference to the relations which had been recognized between the specific heats and atomic weights of solid, simple or compound bodies, he spoke as follows §. “ It is true that these laws, in the case of solid bodies, only apply approximately to simple bodies and those compounds of least complex constitution ; for all others it is impossible to pronounce anything in this respect.” From some remarks of Regnault in reference to carbon || and silicium ^f he considers it possible, or probable with certain elements, that they have a different specific heat in their compounds to that which they have in the free state. 9. In 1840 De la Rive and Marcet published ** investigations on the specific heat of solid bodies. They made their determinations by the method of cooling. They found that, assuming Berzelius’s atomic weights, selenium, molybdenum, and wolfram fall under Dulong and Petit’s law, which they consider as universally valid; but that carbon forms an exception, and they consider it as probable that its true atomic weight has not yet been ascertained. For several sulphides they found a greater specific heat than was calculated for them, assuming that their constituents have in them the same specific heat as in the free condition. They think that for solid as well as for liquid and gaseous compounds the law governing the specific heat is still unknown. A sub- sequent memoir by these physicists treated of the specific heat of carbon in its various conditions. 10. In 1840 H. Schroder made an investigation as to what volumes are to be assigned to the constituents of solid and liquid compounds when contained in those compounds. In his memoirs on the subject, he expressed the view that the specific heat of compounds depends on the specific heats of the constituents in that particular * Ann. de Chim. et de Phys. [3] vol. i. p. 183. t Ibid. p. 132. i Regnault has made known the results of these experiments in 1853 by a preliminary account in the Comptes Rendus, vol. xxxvi. p. 676, and more completely in 1862 in his ‘ Relation des experiences pour determiner les lois et les donnees physiques necessaires au calcul des machines a feu/ vol. ii. p. 3. § Relation, &c. vol. ii. p. 289. || Ann. de Chim. et de Phys. [3] vol. i. p. 205. Ibid. [3] vol. Ixiii. p. 31. ** Ibid. [2] vol. lxxv. p. 113. ft Ibid. [3] vol. ii. p. 121. Poggendoeee’s * Annalen/ vol. 1. p. 553. PBOFESSOB KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 79 state of condensation in which they are contained in the compounds in question. In 1841 *, reasoning from the results of Regnault’s experiments, he endeavoured to show that the atomic heat (that is the product of the atomic weight into the specific heat) of a compound is equal to the sum of the atomic heats for the states of condensation in which the elements are contained in the compound, and to ascertain what atomic heats are to be assigned to certain elements in certain compounds. On the assumption that the atomic heat of metals in compounds is as great as in the free state, he endeavoured to determine the atomic heat of oxygen, sulphur, &c. in certain compounds of these elements with the metals ; he came to the conclusion that an element (sulphur for. in- stance) may in some compounds have an atomic heat different from that which it has in the free state ; and the same element (sulphur or oxygen for instance) may have different atomic heats in different compounds; but the changes in the atomic heat of an element always ensue in simple ratios. I cannot here adduce the individual results which he obtained when he inferred the atomic heat of an element in a compound by subtracting from the atomic heat of the compound the atomic heat of the other elements in it, which he had calculated either from direct determinations of their specific heat, or from previous considerations. The essential part of Schroder’s con- ception is that in this manner the atomic heat of a body, as a constituent of a compound, may be indirectly determined ; and the result is that the atomic heat, at any rate of some elements in compounds, is different from what it is in the free state, and may be different in different compounds, and that the changes are in simple ratios. Schroder considered also that there was probably a connexion between these changes and those of the volumes of the elements, without, however, stating how from the one change the other might be deduced. 11. L. Gmelin (in 1843) considered it as inadmissible, from the chemical point of view, to assign throughout such atomic weights to the elements as to make them agree with Dulong and Petit’s law. Certain exceptions must be admitted. Comparing the specific heats of oxygen, hydrogen, and nitrogen for the gaseous state with the specific heats of other elements in the solid state, he came to the conclusion that if the numbers given in § 2 as the equivalents ordinarily assumed be taken as atomic weights, the atomic heat of hydrogen, of nitrogen, and by far the greater number of the elements is equal to about 3-2 ; several of them twice as great, that of oxygen one-half, that of carbon (as diamond) one-fourth as great. With reference to the dependence of the atomic heats of the compounds on those of the elements, Gmelin expressed the opinion J that in general the elements on entering into compounds retain the atomic heats they have in the free state, but for individual elements, especially for oxygen and carbon, it must be assumed that their atomic heat changes in simple ratios with the compounds into which they enter. * Poggeitdoree’s ‘ Annalen,’ vol. lid. p. 269. f L. Gmelin’s ‘ Handbuch der Chemie,’ 4th ed. vol. i. p. 217. + Ibid. p. 222 : compare an earlier remark of Gmelin which applies to this subject (1840) in the new edition of Gehler’s £ Physikalisches Wbrterbuch,’ vol. ix. p. 1941. MDCCCLXV. N 80 PEOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 12. Wcestyn was also of opinion * that the specific heats of the elements remain unchanged when they enter into chemical compounds. In 1848 he stated as a general proposition ; “ The quantity of heat necessary to raise the temperature of the atomic weight of a body through 1° is equal to the sum of the quantities of heat necessary to raise the temperature of the atoms, and fractions of atoms, through 1°”. If A is the atomic weight and C the specific heat of a compound, alf a2, a3 ... . the atomic weights f, and cz, c2, c3 ... . the specific heats of the elements contained in it, and wz, n2, nz . . . . the numbers which express how many atoms of each element are con- tained in an atom of the compound, then AC =n1alcl -\-n2a2c2-\-nza3cz As a proof of this law, he compared the calculated values of AC of several compounds (metallic iodides and sulphides) and alloys with the observed values, taking Regnault’s determinations of the specific heats of the elements and of the compounds. It follows, further, from that proposition, that if the formula and the values for several compounds are compared with each other, there must be the same differences of the values AC for the same differences of formulae. WtESTYN showed by a number of examples that this is so approximately. By means of this law, the product of the specific heat and the atomic weight for one constituent of a compound may be found, if this is known for the compound and the other constituents. Wcestyn deduced in this way the product for oxygen (by subtracting from the product for different metallic oxides that found for the metals, and from chlorate of potass that for chloride of potassium) to be 2*4 to 2T (0. = 8), and for chlorine 3-0 to 3’5 (Cl. = 17‘75). Wcestyn finally expressed a doubt whether Neumann’s law is universally applicable. He laid stress on the circumstance that when two elements give different products, the difference is also met with in the products for their analogous compounds ; and, for instance, the greater products which mercury and bismuth have in comparison with other elements, are also met with in the compounds of these metals. 13. Garnier (in 1852) developed the viewj, that not only in the case of elements are the atomic weights A § inversely proportional to the specific heats C, but that the same is the case with water || and solid compounds in whose atom n elementary atoms are A contained, if the so-called mean atomic weight — be compared with the specific heat C ; for elements AxC=3, and for compound bodies ^xC= 3 (if 0=8). He endeavoured to prove this from Regnault’s determinations of specific heats. From the latter equa- tion he calculated the specific heat for several compounds. In the case of the basic oxides, sulphides, chlorides, bromides, and iodides, his calculated results agree tolerably * Ann. de Chim. et de Phys. [3] vol. xxiii. p. 295. t Wcestyx based bis considerations on Regnatjlt’s thermal atomic weights. X Comptes Eendus, vol. xxxy. p. 278. § If Begxault’s thermal atomic weights are taken. || I shall in § 93 return specially to the question how often the specific heat of liquid water was compared with that of solid bodies. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 81 with the observed ones ; this is less the case with metallic acids and oxygen salts, for which calculation mostly gives results far too large. Garnier* drew, further, from the above proposition the conclusion, that the atomic weight of hydrogen, chlorine, &c. must in fact be taken only half as great as the equivalent weight ; for only by assuming this smaller atomic weight is the mean atomic weight such that its product with the specific heat is near 3. In 1852 BANCALARif repeated that the specific heat of an atom of a compound body (that is, its atomic heat) is equal to the sum of the specific heats of the individual con- stituent simple atoms, and showed, from a series of examples (oxides, chlorides, sulphates, and nitrates), that, according to that proposition, the atomic heats of many compounds may be calculated in tolerable approximation with those derived from Regnault’s expe- rimental investigations, if, for the elements which he investigated, the atomic heats derived from his determinations be taken as a basis, that is, for oxygen (0 = 8) the atomic heat 1'89; for chlorine (Cl=17*75) 3-21 * for nitrogen (N = 7) 3*11. Cannizaro (in 1858$) has used the proposition, that, in the sense above taken, uni- AC versally -^-=a constant, for the purpose of ascertaining the value of n for the atomic weight of different compounds, and therewith ascertaining the atomic weight of elements which are contained in these compounds. 14. Besides those of Regnault, but few experimental determinations of the specific heats of solid bodies have been published. Bede§ and Bystrom|1 have published inves- tigations on the specific heat of several metals at different temperatures : both sets of experiments were made by the method of mixtures. From the year 1845, Person**, in his investigations on the specific heat of ice, then on the latent heats of fusion, and their relations to the specific heats in the solid and liquid condition, has determined the specific heat for several solid Substances, especially also for some hydrated salts. He worked more especially by the method of mixture. He observedff , in the case of these * Comptes Rendus, vol. xxxvii. p. 130. f An abstract from Memorie della Accademia delle Scienze <li Torino, [2] vol. xiii. p. 287, in the Archives des Sciences Physiques et Naturelles, vol. xxii. p. 81. I only know the contents of this memoir from this abstract. X II Nuovo Cimento, vol. vii. p. 321. Piazza also gives a statement of this speculation in his pamphlet, ‘ Formole atomistiche et typi chimici,’ 1863. I only know this from a notice in the Bulletin de la Societe Chimique de Paris, 1863. § An abstract from the Bulletin de PAcademie des Sciences de Belgique,, vol. xxii. p. 473, and the Me'moires Couronnes par l’Academie de Belgique, vol. xxvii., appeared in the Bericht iiber die Fortschritte der Physik im Jahre 1855, dargestellt von der physicalischen Gesellschaft zu Berlin, p. 379. || Abstract from the Oversigt of Stockholm Yetenskaps-Akademiens Forhandlingar, 1860, in the same Jahr- eshericht, 1800, p. 369. if To the experiments of Dulong and Petit on this subject, mentioned in § 3, Pouiilet’s determinations of the specific heat of platinum at different temperatures must be added (Comptes Rendus, vol. ii. p. 782). ** Comptes Rendus, vol. xx. p. 1457 ; xxiii. pp. 162 & 366. Ann. de Chim. et de Phys. [3] vol. xxi. p. 295 ; xxiv. p. 129 ; xxvii. p. 250 ; xxx. p. 78. tt Peiison expressed this in 1845 (Comptes Rendus, vol. xx. p. 1457), with regard to his determinations of N 2 82 PEOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. salts, that their specific heats may be calculated in close approximation with those found experimentally on the assumption that the constituents, anhydrous salt and water con- sidered as ice, have the same specific heats in them as in the free state. By the same method, Alluard* (in 1859) determined the specific heat of napthalene. ScHAFARixf, lastly, has executed by the method of mixtures a series of experiments on the determi- nation of the specific heats of vanadic, molybdic, and arsenious acids. Quite recently (1863), PapeJ has published investigations on the specific heat of anhy- drous and hydrated sulphates. He worked by the method of mixture, which he mo- dified in the case of salts rich in water, by placing them in turpentine, and observing the increase of temperature produced in the salt and in the liquid by immersing heated copper. As a more general result, Pape finds that for hydrated sulphates of analogous formulse, the products of the specific heats and the equivalents are approximately equal; and further, that with sulphates containing different quantities of water, the product of the specific heat and the equivalent increases with the quantity of water, in sueh a manner, that to an increase of each one equivalent there is a corresponding increase in the product. 15. In the preceding paragraphs I have collated, as far as I know them, the investiga- tions on the specific heat of solid bodies, on the relations of this property to the atomic weight, and on the connexion with the chemical composition of a substance. The views which have been expressed relative to the validity of Dulong and Petit’s § and of Neumann’s laws, and also as to the question whether the elements enter into chemical compounds with the same specific heats which they have in the free state or with modi- fied ones, have been various and often discordant. In this respect it may be difficult to express an opinion which has not been already either stated or hinted at, or which at any rate cannot be naturally deduced from a view previously expressed. The results to which my investigations on the specific heats of solid bodies have led me are the following : — Each solid substance, at a sufficient distance from its melting- point, has a specific heat, which may vary somewhat Avith physical conditions (tempe- rature, greater or less density, amorphous or crystalline conditions, &c) ; yet the variations are never so great as must be the case if a variation in the specific heat of a body is to the specific heat of crystallized borax and of ordinary phosphate of soda. He has subsequently published the results of his experiments for the latter salt (Ann. de Chim. et de Phys. [3] vol. xxvii. p. 253), hut I cannot find the number which he found for crystallized borax. * Ann. de Chim. et de Phys. [3] vol. lvii. p. 438. t Berichte der Wiener Akademie der Wissenschaften, vol. xlvii. p. 248. X Poggendorff’s ‘ Annalen,’ vol. cxx. pp. 337 & 579. § The universal validity of this law was also defended by Brehow, “ On the relation of the Specific Heat to the Chemical Combining Weight.” Berlin, 1838. I only know this paper from the mention of it in the new edition of Gehler’s * Physicalisches Worterbuch,’ vol. x. p. 818. It is also admitted by Manx, in his attempt to deduce this law from the undulatory theory of heat. (1857 : Schxomixch and Witzschel’s 4 Zeitschrift fur Mathematik und Physik,’ II. Jahrgang, p. 280) ; and by Stefan, in his investigation on the bearing of this law on the mechanical theory of heat (1859 : Berichte der Wiener Akademie, vol. xxxvi. p. 85). PEOFESSOK KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 83 be held as a reason for explaining why the determinations of the specific heats of solid elements do not even approximately obey Dulong and Petit’s law, nor those of solid com- pounds of analogous chemical constitution Neumann’s law. Neither law is universally valid, although I have found that Neumann’s law applies in the case of many compounds of analogous atomic composition, to which, on account of their totally different chemical deportment, different formulas are assigned ; and even in cases in which these laws have hitherto been considered as essentially true, the divergences from them are material. Each element has the same specific heat in its solid free state and in its solid com- pounds. From the specific heats to be assigned to the elements, either directly from experimental determination, or indirectly by calculation on the basis of the law just stated, the specific heats of their compounds may be calculated. I show the applicability of this by a great number of examples. In reference to this calculation of the specific heats of solid bodies I may here make a remark. The agreement between the results of calculation and experiment is often only approximate ; it is then natural to urge that the two ought really to agree more closely. To that the question may be allowed : What means are there of even approxi- mately predicting and calculating beforehand the specific heat of any inorganic or organic solid compound when nothing but its empirical formula is given 1 to which among the numbers OT, 0'2, 0-3 may it come nearest! The cases in which differences exist between calculation and observation, enumerated in § 103 to 110, may be set against this uncertainty. My proof of the propositions given above is based on determinations made by earlier inquirers, and on a not inconsiderable number of my own. I first describe the method by which I worked, and then give the results which I have obtained by its means. PAET II. — DESCRIPTION OF A METHOD OF DETERMINING THE SPECIFIC HEAT OF SOLID BODIES. 16. I have worked by the method of mixture. It is not necessary for me to discuss the advantages which this method has over that of the ice-calorimeter, at any rate in requiring smaller quantities ; nor, as compared with the method of cooling, need I dis- cuss the uncertainties and differences in the results for the same substance, which are incidental to the use of this method, and which Regnault has detailed*. The method of mixtures has been raised by Neumann and by Regnault to a high degree of perfection. Although by Neumann’s method it is possible to determine more accurately the temperature to which the body investigated is heated, Regnault’s method allows larger quantities to be used. Regnault’s process gives the specific heats of such substances as can be investigated by it as accurately as can at all be expected in the determination of this property. In the case of copper and steel, it is not merely possible to determine their specific heats by its means, but also to say whether and how * Ann. de Chim. et de Phys. [2] vol. Ixxiii. p. 14 ; [3] vol. ix. p. 327. 84 PEOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. far there is a difference in the first metal according as it has been heated or hammered, and in the second, according as it is soft or hard. It may be compared with a gonio- meter, which not only measures the angles of a crystal, but also the differences in the angle produced by heat ; or it may be compared to a method for determining the specific gravity of a body, by which not only this property, but also its changes with the tem- perature may be determined. But along with such methods, simpler ones, though perhaps less accurate, have also their value. Which method is the most convenient or which ought to be used in a given case, depends on the question to be decided by the experiment, or on the extent to which the property in question is constant in the sub- stance , examined. In regard to the relations of the specific heat of solid bodies to their atomic weight and to their composition, Regnault’s determinations have shown that both Dulong and Petit’s and Neumann’s law are only approximate, and that even the accuracy in determining the specific heat which Regnault attempted, and obtained, could not show that these laws were quite accurate. Although the description of Regnault’s mode of experimenting is so widely known, yet it cannot be said to have become the common property of physicists, or to have found an entrance into the laboratories of chemists, to whom the determination of the specific heat is interesting from its relation to the atomic weight. Very few experiments have been made by this method other than the determinations of Regnault. The method depends on the use of an apparatus which is tolerably complicated and takes up much room. Each experiment requires a long time, and for its performance several persons are required. Regnault has usually worked with very considerable quantities of the solid substance, and in by far the majority of cases at temperatures (usually up to 100°) which many chemical preparations, whose specific heats it is important to know, do not bear. In the sequel I will describe a process, for the performance of which the apparatus can be readily constructed, and for which one operator is sufficient ; by which, moreover, the determination of specific heat can be made with small quantities of the solid substance and at a moderate temperature. But the method as I have used it has by no means the accuracy of that of Regnault. In § 18 I shall discuss the advantages for which some of the accuracy which characterizes Regnault’s method is sacrificed ; but I may here remark that the results obtained by the method which I have used are capable of increased accuracy, provided the experiments are executed on a larger scale and within greater ranges of temperature. 17. The principle which forms the basis of my method is as follows: — To determine the total increase of temperature produced when a glass containing the substance to be investigated, covered by a liquid which does not dissolve it, the whole previously warmed, is immersed in cold water ; to subtract from the total increase of temperature that due to the glass and the liquid in it, and to deduce from the difference, which is due to the solid substance, its specific heat. If, in regard to gain or loss of heat, the glass, in so far as it comes in contact PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 85 with water, is equivalent to x parts of water, if f is the weight of the liquid in it, y its specific heat, m the weight of the solid substance, M the weight of the water in a calo- rimeter, including the value in water of the immersed part of a thermometer and of the calorimeter, T the temperature to which the glass and its contents have been heated before immersion in water, and T' the temperature to which the glass sinks when im- mersed in the water, while the temperature of the latter rises from t to t', then the specific heat (sp. H.) of the solid substance is TT M(f—t) — [r+fy) . (T— T) P‘ 11 m(T-T') In the sequel I shall discuss more specially the manner in which the individual mag- nitudes in this equation were determined : I will first give a description of the apparatus and method which I used*. The glass vessel in which the substance is confined (Plate XX. a in fig. 1) is a tube of glass, the bottom of an ordinary test-tube. In it fits, but not air-tight, a cork c, which is pressed between two small brass plates that are screwed to a wire b. The solid sub- stance to be investigated, in the form of thin cylinders, or in small pieces the size of a pea, along with a liquid of known specific heat, which does not dissolve it, are placed in the tube in such a manner that the liquid covers the solid substance, and that there is a space between the liquid and the cork when it is inserted. The glass, when the cork is fitted, may be suspended to the balance by the wire b. Three weighings (1) of the empty glass, (2) after introducing the solid substance, and (3) after introducing the liquid, give the weight of the solid substance (in) and of the liquid (f). The heating apparatus (fig. 1) serves to raise the temperature of the glass with its contents. The glass is dipped in a mercury-bath A near its upper edge, and retained by a holder E. The mercury-bath, which consists of a cylindrical glass vessel, is sus- pended by means of a triangle round the neck of the vessel in an oil-bath B, which stands on a tripod C, and can be heated by a spirit-lamp D. A thermometer fixed to the holder F, is also immersed in the mercury-bath. The flame of the spirit-lamp may be regulated so that the thermometer d indicates the same temperature for a long time $. If it may be assumed that the contents of the glass a have also risen to this temperature, then the wire b being firmly held in the right-hand by its hook, and the clamp of the holder E in the left, the glass a is rapidly removed from the heating vessel to the calorimeter H (fig. 2). This is almost the only part of the entire experiment which really requires much practice ; the transference of * All figures on tlie Plate are one-third of the natural size. f Fig 7 shows in section how the glass with its contents and the thermometer dip in the mercury- bath and this in the oil-hath. + In order to obtain temperatures constant at about 50°, a spirit-lamp with a thin wick is used, and this is pressed in the sheath so that the alcohol-vapour above it burns with a very small flame. The position of the wick and the intensity of the flame may be conveniently regulated if the upper part of the wick is surrounded by a spiral of thin copper wire whose ends project from the sheath. 86 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. the glass a from the one vessel to the other must be effected in an instant, and none of the liquid in the glass must touch the cork. The calorimeter H stands upon a support G (fig. 2)*, on which there is an oval metal plate o. In this there are three depressions, in which fit the three feet of the calori- meter (they are made of very thin hard brass wire). The calorimeter is oval-shaped, and is made of the very thinnest brass plate. In it a brass stirrer fits, made of two parallel plates of brass of the same thinness, which are joined below by thin wires, and provided with a thin wire ending in a little button i, which serves as handle. The plates of the stirrer are perforated in such a manner that the glass a and a thermometer can be passed through them. Fig. 4 shows more distinctly the construction of the stirrer, also the section of the calorimeter. For the experiments, the calorimeter is always filled, as nearly as possible, with the same quantity of waterf. The stirrer is immersed, and a thermometer f dipping in the water gives its temperature, which is kept uniform by an upward and downward uniform motion of the stirrer. When the tube a is brought into the water of the calorimeter, it is fastened^ in the clamp of the holder K, which is arranged like the pincettes used for blowpipe experiments, so that it stands on the bottom of the calorimeter, and then the stirrer is set to work. This motion of the stirrer, and therewith of the water, must be moderate and uniform in all experiments ; this is of some importance for the uniformity and comparability of the experiments. The temperature indicated by the thermometer f rises and soon attains its maximum, which continues for some time, and can be observed with certainty. With this the experiment is concluded. The tube a can be taken from the calorimeter, dried, and used for a new experiment. The increase of temperature produced in the calorimeter by the tube a and its con- tents, would be incorrectly given if the warmth of the body of the operator, who moves the stirrer and observes the thermometer, acted on the calorimeter. This is prevented by a glass screen g g g g, fig. 2, which is fitted in the brackets h h, and above which the handle of the stirrer projects. 1 8. This process for determining the specific heat of solid bodies, the details of which are more minutely discussed in the sequel, has advantages over those hitherto prin- * In making the experiment, the actual distance between the calorimeter and the heating apparatus must be greater than is indicated in the figure, but not so great that the glass a cannot, by a rapid motion of the arm, be transferred from the mercury-bath to the calorimeter. t This is most conveniently effected by laying across it a bridge with a stem directed downwards (fig. 3), and adding water until it touches the point of the stem ; and the calorimeter, which now contains almost the requisite quantity of water, is placed on the balance, and the filling completed by means of the dropping-flask (fig. 8). The construction of the latter is readily intelligible : it is held by the cork between two fingers, and by approaching the hand to the bottom of the flask water commences to drop. When the flask is not in use the tube, which fits air-tight in the cork, is raised, so that it does not dip in the water, and thus the water is prevented from escaping. + Fig. 5 shows in a section the glass a, with its contents, and the thermometer / immersed in the water of the calorimeter. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 87 cipally used, which I will here mention. The use of the mercury-bath makes it possible readily to produce, and maintain for any adequate length of time, any temperature de- sirable in such experiments. The mercury-bath* shares with the air-bath the advantage that, to the substance heated in it (in this case the tube and contents), nothing adheres when it is removed which might influence the thermal effect in the calorimeter. It has over the air-bath the advantage, that any body placed in it takes the tempera- ture of the surrounding medium much more quickly through its entire mass. The communication of heat to the solid substance is materially promoted by the circulation of the liquid between its particles ; the time necessary for the entire contents of the glass to become equally heated is a very short onef. Moreover this very circulation of the liquid between the particles of the solid ensures a quicker and more uniform transmission of the heat of the contents of the glass to the water of the calorimeter ; the maximum temperature of this water is soon attained^, although the transmission of the excess of temperature must take place through the sides of the glass. * In 1848 I already used such a one for heating liquids enclosed in glass tubes, in determining their specific heats (Poggendorff’s ‘ Annalen,’ vol. lxxv. p. 98). t In experiments on the scale on which I made them, when the mercury-bath had once been raised to the requisite temperature, it only required ten minutes’ immersion of the glass in the bath to impart to it the tem- perature of the bath. A more prolonged heating was found to be useless in all cases in which I tried it. In the experiments to be subsequently described, the heating was continued about ten minutes ; in most cases less would have been sufficient. In Regnatjlt’s experiments (Ann. de Chim. et de Phys. [2] vol. lxxiii. p. 22), in which the substance (in much larger quantities it is true) was heated in a space nearly surrounded by steam, a thermo- meter placed in the substance indicated after about two hours an almost constant position (always one or two degrees lower than the temperature of the steam) ; and then it was found convenient to continue this heating for at least an hour, in order to see that the temperature did not change, and to be certain that the substance had the temperature indicated by the thermometer throughout its entire mass. In Neumann’s experiments, the space in which the substance to be heated is contained is smaller and more completely surrounded by vapour. The time necessary for heating the substance uniformly must be smaller, and the temperature must be nearer that of the surrounding vapour. According to Pape (Poggendorff’s ‘ Annalen,’ vol. cxx. p. 352), a thermometer placed in the above space, if surrounded by steam for forty-five to sixty minutes, gives exactly the temperature of this steam. + In several experiments I determined the time which elapsed between immersing the glass with contents in the water of the calorimeter and its attaining a maximum. Under the circumstances, which I subsequently give more specially, and which, as far as possible, were maintained in all experiments, this time was always less than two minutes, if the liquid could circulate between compact pieces of the solid substance. What I have said above justifies, I think, my not having made, in experiments with such substances, a correction for the loss of heat which the calorimeter experiences between the moment of immersing the glass and the establishment of a maximum temperature. In substances which form a fine powder or a porous mass, or in general in cases in which the circulation stagnates, the maximum temperature is more slowly attained, the above loss of heat is more con- siderable, and the numbers for the specific heats are then somewhat too small. I shall recur to this again in enumerating the experiments in § 41 with chromium, and in § 52 with chloride of chromium. In a few cases I have endeavoured to diminish this error, and to promote the circulation of the liquid by pressing the porous substance into small disks. I must leave it as an open question whether more accurate results would not be obtained for such substances if they were formed by means of a suitable cement into compact masses, and then the thermal action of the cement thus added taken into account. MDCCCLXV. 0 88 PROFESSOR KOPP OjST THE SPECIFIC HEAT OF SOLID BODIES. The apparatus which I have just described is very simple. It is readily constructed; the chief point is to have two thermometers which have been compared with each other, one of them (f) graduated in tenths of a degree, while on the other ( d ) the tenth of a degree can be observed with certainty. The apparatus does not require much space ; yet, while the experiment is being made, rapid changes in the temperature of the sur- rounding air must be avoided. One observer only is required (all the experiments described in the sequel have been made without assistance). The experiments which I shall communicate prove that, by means of this apparatus, the specific heat of solid substances, even when only small quantities are taken (in most cases I worked with only a few grammes), may be determined with an accuracy not much less than that attained with larger quantities in more complicated processes. 19. Yet, it is true, the accuracy of the results obtained by this process appears to be inferior to that attainable by the use of Neumann’s or of Regnault’s methods. I have investigated many substances, determinations of which have also been made by these physicists. I do not find that the numbers I have obtained deviate in one special direc- tion from those which these physicists have found, which moreover sometimes differ considerably among themselves * ; but that the certainty of the results I have obtained is less, is shown by the fact that the results of different experiments with the same substance agree less closely with one another than do those 'of Regnault and of Neumann. That my determinations are less accurate is probably least due to the circumstance that I did not use certain corrections, for instance, that I did not allow for the loss of heat in the calorimeter between the time when the heated body was immersed and the maximum temperature was attained f. I have endeavoured to diminish the uncer- tainty of the results from this source by having the temperature of the water in the calori- meter, before immersing the heated body, somewhat lower than that of the surrounding air. I have endeavoured to ensure comparability in my results for different substances by always operating as much as possible under the same circumstances ; that is, I endeavoured always to produce in the water of the calorimeter the same excess of temperature over that of the surrounding air. Without depreciating the interest and value of such corrections, I think that their application may be omitted if them practical importance is inconsiderable, and the increased difficulties which they necessitate pro- portionally large. It must be considered, in reference to such corrections, how far the accuracy, which the results obtained by their means claim, is not more apparent than real $. And further, that these corrections, where the conditions for their application really exist, are not considerable ; while, where they exert a considerable influence on the result, they may be uncertain, because the suppositions made in their development * Pape, in Poggendokee’s ‘Annalen,’ vol. cxx. p. 579, discusses the probable causes of these differences. f Another correction, which appears to me to he more important for the experiments in question, is, that the contents of the glass at the time at which the temperature of the water is at its maximum may he at a some- what higher temperature. This I have approximately taken into account. Compare §§ 23 & 24. X It is unnecessary to adduce examples where such corrections, proceeding from as comprehensive a basis as PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 89 are less applicable. But more especially can such corrections be disregarded when, as in the case with my determinations, other circumstances diminish more materially the accuracy of the results to be obtained. Such circumstances in my experiments are, that I worked on a small scale in every respect. I could only heat the solid investigated together with a liquid to 50°, and in many cases not even to this. In Neumann’s and in Regnault’s experiments, on the contrary, the solid was usually heated to near 100°, and the difference in temperature, T— T' (compare § IT), obtained in the latter experiments was usually thrice as great as in mine. In Regnault’s experiments (in Neumann’s the details are not given) the quantity of substance taken was, on the average, twenty times as much, and the weight of water in the calorimeter about eighteen times as much as in mine * : hence in the latter experiments the unavoidable accidental errors of observation must be greater than in the former. But there is a still more important circumstance which makes the accuracy to be hoped for from my experiments less than that to be expected from Regnault’s and Neumann’s experiments. In the latter methods the increase in the temperature of the water of the calorimeter is entirely, or is almost entirely produced by the solid under examination. In my experiments, on the contrary, this increase is produced by the glass, the solid, and the liquid in the glass. The thermal action due to the solid is only a part of the entire thermal action observed, and if from the latter that due to the liquid and to the glass is subtracted, all uncertainties in the assumptions as to the thermal action of the possible, lose their significance from necessary simplifications, and tbeir practical importance becomes finally very slight. The amount of correction is then to be pronounced as having no influence on the final result. It is more important to take into account the following. The trustworthiness of the specific heat to be assigned to any particular compound depends upon the certainty of the determination of the physical property, and upon the certainty of the knowledge of the composition of the body in question ; that is, in how far this compound corresponds to a given formula. The greatest trouble which can be taken in that determination, the consideration of all sources of error which are possible in the physical experiment, the most complete exposi- tion of the corrections which by developing conclusions from more or less certain assumptions may be formu- lated in one expression, and the most conscientious application of these corrections, — all this may be paralyzed by the' circumstance that the composition of the body in question is not, as it were, the ideal, not corresponding accurately to the formula. The partial substitution, if even to a very small extent, of one constituent by an isomorphous one, the attraction of water by a hygroscopic substance before and during the experiment, the presence of some mother-liquor in a crystallized salt, the loss of some water in drying a hydrated substance, so that this has not exactly the composition corresponding to the formula, — all these sources of error, which can scarcely be taken into account, may easily exercise an influence on the final result, whose magnitude far exceeds that of certain corrections applied to the physical part of the determination. It lies in the nature of the case that in such investigations, in some cases bodies of well-known, in other cases bodies of less well-known composi- tion are taken. I tried to be certain what substances could be considered as of definite composition and what of doubtful composition, especially where the relations between the specific heat and the atomic weight or che- mical composition were under discussion. * About sixty solids have been investigated both by Regxaglt and myself; for about thirty the weights which he used in his determinations are twenty times as much as in mine or more. 0 2 90 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. liquid and that of the glass are concentrated on the remainder, on the thermal action of the solid substance from which its specific heat is to be deduced. The results obtained by my method are less accurate when the residue is only a small fraction of the total result from which it is deduced. In individual cases, where this was unavoidable, I shall have to remark upon it. It may be said in favour of my method that, for a number of solid substances, no other method yet attempted is applicable either at all or with more prospect of a suc- cessful result. But this is less important than the proof furnished by my examination of very many substances, whose specific heat has been already determined by Neumann and by Regnault, that the specific heat of bodies may be determined by my method with an accuracy quite sufficient for many comparisons. But there are cases in which it is even advantageous not to heat the solid alone, but in conjunction with a liquid, and to bring them together into the water of the calorimeter. The chemical nature of the solid may necessitate this ; as, for example, when it readily alters on being heated in the air (compare § 34 in reference to amorphous boron) ; its physical structure may also render it desirable, as for instance if the substance has a large surface as compared with its mass, or is so porous that the thermal action due to humectation, and first observed by Pouillet *, takes place. Regnault has shown that this may be considerable f ; he states that for this reason the specific heat of some substances is found about too great. He appears to have estimated this thermal action by ascertaining the increase of temperature produced in the water of the calorimeter when the porous substance, whose temperature is that of the water and of the surrounding air, is dipped in it. But this action is probably far more considerable if, while heated, it is immersed in the water, because it then contains less air confined on its surface and in its pores J, and surface action can then act more intensely upon the liquid. The influence of this source of error cannot be measured exactly. It is unequal in different substances. In platinum it is small (Regnault found by his method that the specific heat of spongy platinum did not materially differ from that of massive pieces), while it may be con- * Ann. de Chim. et de Phys. [2] vol. xx. p. 141. t Ann. de Chim. et de Phys. [3] vol. i. p. 133. Regnault preferred to immerse the heated porous sub- stances, when they could be obtained in coherent pieces, directly in the water of the calorimeter. If they were enclosed in thin tubes and immersed, the equalization of temperature proceeded too slowly. Regnault abstained from enclosing at the same time a sufficient quantity of water in the tube to promote the circulation, because in that case the thermal action of the solid was only a fraction of that of the water added, on which the entire source of error falls. Regnault found also (ibid. p. 142) that in immersing anhydrous baryta, strontia, and lime in most carefully dehydrated oil of turpentine, there is such a thermal action that no useful result is to be obtained by his method for these oxides. i. To the examples already known, which show what influence temperature exerts on the quantity of air absorbed in a porous body, Regnault has added a very instructive one (Ann. de Chim. et de Phys. [3] vol. lxiii. p. 32). If amorphous boron, formed into disks by pressure in a steel mortar, was strongly cooled and then immersed in the water of the calorimeter (at the mean temperature), so considerable a disengagement of absorbed air was produced, that Regnault was compelled to give up the determination of the specific heat by this method. PROFESSOE IvOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 91 siderable for porous charcoal (in fact Pouillet’s experiments make this probable). This source of error is excluded in my method. 20. In order to appreciate the trustworthiness of the results arrived at by my mode of experiment, it is important to state with what amount of accuracy the data of obser- vation and the ancillary magnitudes were determined. I will give this statement in what now follows. Por observing the temperature of the water in the calorimeter I used thermometers made by Geissler of Bonn, which the kindness of Professor Buff, Director of the Phy- sical Cabinet in Giessen, placed at my disposal. In these thermometers the tube consists of a fine glass thread drawn out at the lamp. The bulb is cylindrical, very thin in the glass, and contains but little mercury. On one ( b ) 1° C. corresponds to a length of almost 5 millims. on the scale, and on the other (r) to almost 4*5 millims. Tenths of a degree can be read off directly on the scale, and it is easy to learn to estimate hundredths safely. I have repeatedly compared these two thermometers, between 7° and 24°, with two normal thermometers of my own construction, which agree very well with each other, and on one of which a division corresponds to 0o,4878, and the other to 0o,4341. The differences of the indications between the Geissler’s thermometers and these could be considered as constant within those limits ; for the differences thus observed all the readings made with the Geissler’s thermometers had to be corrected to make them comparable with the indications of the normal ther- mometer. The temperature of the mercury-bath was ascertained by means of one of these normal thermometers, and the indications of this thermometer immersed in the bath (d in fig. 1.) corrected for the lower temperature of the mercury thread out of the bath ; this latter temperature was given with adequate approximation by the second thermometer, e. 21. The weight of the thin sheet-brass calorimeter, together with stirrer, was 11T45 grms.* Taking the specific heat of brass, according to Begnault, at 0-09391, the calorimetric value in water of this mass of metal is 1 -046 grm. Considering that the calorimeter in the experiments was not quite filled with water, but about ^th remained empty, even after introducing the tube, I put the value in water at 0-872. In determining the calorimetric water value of the immersed parts of the thermo- meters r and b, the following experiments were made. The weight of water in the calorimeter, together with the reduced weight of the metal, was 30-87 grms. When the thermometer r heated to 330,86 was immersed, the temperature rose from 10°-73 to 10o,85 ; the immersion of the thermometer b at a temperature of 37°-53 caused a rise from 10°-61 to 10°-76. In both cases the temperature of the water was indicated by means * At the beginning of these investigations. During their progress the calorimeter was cleaned and dried with bibulous paper a countless number of times, so that its weight diminished by about 0-04 grm. in the course of the experiments. In determining the weight of water used in each experiment, the weight which the calorimeter actually had at the time was taken as basis. 92 PKOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. of the other thermometer, the reduced value of which might be neglected under these circumstances. These experiments gave 0T6 as the reduced value of the thermometer r, and 0T7 as the reduced value of the thermometer b. The thermometers have very nearly the same dimensions. Hence I put the reduced value of the calorimeter (that is, of the part of the metal concerned), of the stirrer, and of the immersed part of the thermometer at 1*04 grm. Even if this determination is a few tenths out, it is scarcely appreciable as compared with the quantity of water in the calorimeter. In all following experiments this was between 25-85 and 25-95 grms. All the subsequent determinations depend on fixing differences of weights and of temperatures. The accuracy of the results depends on the precision with which both kinds of magnitudes are ascertained ; and it is useless to determine the weights to ywoo or nearer, if the differences in temperature cannot be determined more accurately than to -200 or -3^0. I have weighed to centigrammes instead of to milligrammes, by which the time necessary for the weighings was much shortened, and their accuracy not materially lessened. 22. The reduced value x remained to be determined of the glasses (cylindrical tubes of thin glass, see § 17), or, rather, of that part which was immersed in the water of the calorimeter, the quantity of which was always the same. In the following, T is the temperature to which the glass in the mercury-bath was heated (compare fig. 1), M the quantity of water in the calorimeter + the reduced value in water of the other parts of the latter, which required to be taken into account, t the temperature of the water in the calorimeter when the glass was immersed (fig. 2), and r the temperature to which the water became heated, and which must be considered as that to which the glass cooled*. We have then M(r-<) X~ T-r In my experiments I used three glasses, which may be called 1, 2, and 3. To ascer- tain the reduced value of glass 1, I made the following determinations : — Temperature of Air 15°-8. T. r. t. M. X. 0 0 grms. 78-54 17-23 15-72 26-98 0-664 74-38 17-16 15-78 26-97 0-651 75-51 17-14 15-72 26-92 0-655 76-06 17-15 15-73 26-945 0-649 77-32 17-22 15-74 26-96 0.664 Mean . . 0-657 * If the cork which closes the glass, and by means of the wire passing through it enables it to he handled, is moist, incorrect and discordant values are obtained for it, owing to the evaporation of water in the empty glass so iong as this is in the mercury rbath, and to the condensation of aqueous vapour in the glass when it is immersed in the calorimeter. PROFESS OE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES, 93 I subsequently made a second series of experiments to determine the reduced value for glass 1, which gave the following results : — Temperature of the Air 19°-9-19°-8. T. r. t. . M. X. 0 o o grms. 78-50 21-32 19-93 26-99 0-656 81-86 21-47 20-03 26-98 0-643 80-42 21-43 20-02 26-98 0-645 79-77 21-42 20-03 26-935 0-642 80-14 21-51 20-12 26-955 0-639 Mean . . 0-645 The mean of these two means, 0-657 and 0,645, gives as the reduced value in water of glass 1, 0-651 grm. To obtain the water value for glass 2, I made the following determinations : — Temperature of the Air 12°-0-12°-5. T. r. t. M. X. 0 o o grms. 75-87 13-53 12-43 26-94 0-475 77-05 13-46 12-31 26-96 0-488 76-71 ' 13-68 12-54 26-975 0-488 75-97 13-76 12-65 26-95 0-481 78-60 13-83 12-62 26-95 0-503 Mean . 0-487 The reduced value for glass 2 is hence = 0487 grm. This glass broke before I made a second series of experiments to ascertain its reduced value. I made two series of experiments to determine the reduced value of glass 3. The first gave the following results : — Temperature of the Air 190,3-19°-5. T. r. t. M. X . O o o grms. 81-00 20-33 19-31 26-98 0-454 80-03 20-83 19-84 26-965 0-451 80-22 20-93 19-94 26-98 0-451 84-06 21-04 20-02 26-945 0-436 81-90 20-93 19-93 26-975 0-442 Mean . . 0-447 94 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. The second series of experiments gave the following results : — Temperature of the Air 19°-9-19°*8. T. r. t. M. X. 0 grms. 80-41 21-08 20-06 26-965 0-464 79-64 21-10 20-09 26-965 0-465 79-98 21-12 20T2 26-96 0-458 80-22 21T2 20-12 26-985 0-457 7953 21-10 20-12 26-965 0-452 80-52 21-13 20-14 26-96 0-450 Mean . . 0-458 The reduced value of glass 3 = 0453 grm., the average of the mean numbers of both series of experiments. 23. In those experiments in which a glass containing a liquid and perhaps a solid substance is immersed, while warm, in the water of the calorimeter, it may be asked if, when the water has become heated to a certain maximum temperature, the contents of the glass have actually cooled to the same temperature. In earlier experi- ments made by the method of mixture, it was at once assumed that the temperature assumed by the water of the calorimeter after immersing the solid was actually that also to which the immersed body sank. Neumann has taken into account that the immersed body, when the water shows its maximum temperature, may have a somewhat higher temperature *. Avogadro has also taken this into account f, and Regnault has also allowed for this circumstance in the case in which the mass, immersed in the water of the calorimeter, is a bad conductor of heat J. A correction for this fact is certainly inconsiderable and unnecessary if the immersed body conducts heat well, and the range of temperature through which it cools in the liquid is great. This interval of tempera- ture was in my experiments considerably smaller than in those of Neumann and of Regnault ; and as in my experiments the excess of heat of the contents of the glass had to pass through its sides to the water of the calorimeter, it might be doubted whether, when the temperature of the water was at its maximum, this temperature could be considered as that of the contents of the glass. I have endeavoured to answer these questions experimentally. A glass, such as was used for holding the solid investigated and a liquid, was filled with water, and a per- forated cork fitted, by means of which the glass could be handled, and which permitted the introduction of a thermometer into the water within the glass. The glass filled with water was warmed, and then placed in the calorimeter filled with water ; a thermo- meter A, passing through the cork, showed the temperature of the water in the glass ; * In the memoirs mentioned in § 4, Pape has also discussed and applied the correction to he made for the above circumstance (P oggexdokfe’s •' Annalen,’ vol. cxx. p. 341). t Ann. de Chim. et de Phys. [2] vol. lv. p. 90. ■ ± Ibid [2] vol. lxxiii. p. 26. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 95 a second, B, showed that of the calorimeter water. If the glass filled with the warmer water is immersed in the cold water, the following circumstances are observed*. A sinks very rapidly, while B rises more slowly ; if B shows the maximum temperature for the water of the calorimeter (this temperature being called ^'), A gives a higher temperature (T) for the contents of the glass. B then slowly sinks and A follows it, while the difference between if and T' always becomes smaller. In the two following series of experiments I have endeavoured to determine by how much, under certain conditions, the temperature T' of the water in the glass exceeds the maximum temperature if of the water in the calorimeter when this maximum temperature as such is observed. I obtained the following results: the temperature of the air in the experiments was 13°-2-13°-5. Experiments with Glass 1. Experiments with Glass 2. T'. t\ Difference. T'. ?. Difference. 15-51 15-13 d-38 15-71 15-50 0-21 14-96 14-72 0-24 15-96 15-65 0-31 16-11 15-94 0-17 15-16 14-91 0-25 15-56 15-36 0-20 14-76 14-47 0-29 14-24 14-05 0-19 14-66 14-33 0-33 15-96 15-64 0-32 15-56 15-24 0-32 A closer agreement in the numbers expressing the difference between T' and if is difficult to attain, since a certain time is necessary to observe the occurrence of the maximum temperature, and during the time in which the thermometer B remains con- stant, the thermometer A still sinks ; according to the moment at which the maximum temperature is considered to be established, this difference may be obtained different, and the smaller the later the observation is made. Moreover the magnitude of this difference between T' and if depends on the difference between t and the temperature of the air. I have always endeavoured to work under the same circumstances, and especially to arrange the experiments so that the maximum temperature of the water in the calorimeter did not exceed by more than 2° the temperature of the air f. For these experiments and the apparatus which I used, I assumed, on the basis of the preceding experiments, that if the water of the calorimeter had assumed its maximum temperature t', the contents of the glass were 0o-3 higher ; that is, I put throughout T', the temperature to which the contents of the glass immersed in the calorimeter had fallen, =tf'4-0°-3. 24. It is a matter of course that, in introducing this correction for obtaining the tem- * In these experiments, in order to ensure uniformity in the temperature of the water, the stirrer was kept in continual motion, and the same process followed as in ascertaining the specific heat. t A preliminary experiment shows how cool the water in the calorimeter ought to he. Water which is somewhat cooler than the surrounding air, may he kept in stock for such experiments by placing it in a cylin- drical flask covered externally with filtering paper, and standing in a dish of water, so that the paper is always moist. To warm the water in the calorimeter, it was merely necessary, with apparatus of the dimensions I used, to lay the hand on it for a short time. MDCCCLXV. P 96 PKOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. perature of the contents of the glass at the time the maximum temperature has been attained in the calorimeter, it is unnecessary to give the indications of T' in hundredths of a degree; and since the temperature T, to which the glass with its contents was heated in the mercury-bath, only serves to deduce the difference T — T', it is unimportant in giving this temperature to do so in hundredths of a degree. The accuracy of the determinations of specific heat, in so far as it depends on determinations of temperature, is limited by the accuracy with which the difference of T— T' and t!—t are determined (where t is the original temperature of the water in the calorimeter, and the other letters have the meanings previously assigned to them). To have one of these differences very accurately, while the other is much less accurately determined, avails nothing for the accuracy of the final results. It is at once seen that in my experiments, and especially in those of Neumann and Regnault, the hundredths of a degree have a greater signifi- cance for the small difference tf— t, than the tenths of a degree for the great difference T-T'. The correction for educing the value of T', which I have just discussed, is of course more important the smaller the difference T— T' ; for most of my experiments in which this difference is about 30°, the significance of this correction is inconsiderable, if the con- tents of the glass be a good conductor. I give a few numbers. The experiments given in § 25 on the specific heat of mercury, which, by using this correction, give it at 0‘ 0335 in the mean, give it = 0-0331 if this correction is neglected, that is, T' made=^. The fourth series of experiments, given in § 27, for determining the specific heat of coal- tar naphtha A, give it at 0-425 when this correction is made, and at 0-420 when it is omitted. The first series of experiments in § 33, for determining the specific heat of sulphur, give it at 0-159 when this correction is used, and at 0-152 when it is neglected. Whether in all such cases T' is put —t\ or=£,o+0°-3, is of inconsiderable importance. The correction in question is inadequate if the substance in the glass is a bad conductor ; for example, when the solid in the glass is a pulverulent or porous mass, in which the moistening liquid stagnates (compare § 18). That, under such circumstances, the numbers obtained for the specific heat are found somewhat too small must be remembered in § 41 in the case of chromium, and in § 52 in the case of chloride of chromium. Too small numbers are also obtained, if in the experiments the maximum temperature of the cooling water exceeds that of the air by much more than 2°. Such experiments are not comparable with the others, for example, with those made for the purpose of ascer- taining the ancillary magnitudes occurring in the calculation of the results ; for them this correction is inadequate, and the loss of heat which the contents of the calorimeter ex- periences between the time which elapsed between immersing the glass and the establish- ment of the maximum temperature is too great. By individual examples in § 25 in the case of water, in § 39 in the case of copper, and § 41 in the case of iron, I shall call to mind how this source of error may give somewhat too small numbers for the specific heat ; but I have always tried to avoid this error, since I saw its importance in my first preliminary experiments. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 97 25. I first attempted to test my method by some experiments in which water or mercury was placed in the calorimeter. For the specific heats of these liquids the fol- lowing numbers were obtained, calculated by the formula tt_M (t' — t)—X (T — T') P* /(T-T') in which the signification of f is manifest from what follows, that of the other letters from what has been given before. In the experiments in which a readily vaporizable liquid was contained in the glass, such as water, or coal-tar naphtha, a sensible formation of vapour took place, although the temperature did not exceed 50°. If the glass containing the liquid was heated in the mercury-bath (compare fig. 7), vapour was formed in the empty space below the cork which served as stopper; if the glass was then brought into the water of the calorimeter, this vapour condensed and settled partially on the stopper. The stopper did not act materially on the water of the calorimeter (see fig. 5). The quantity of liquid in the glass which acted directly on the water of the calorimeter, decreased somewhat in each experiment ; but this decrease is very inconsiderable. In the following experiments y denotes first the weight of the liquid in the glass at the com- mencement of the experiment, and at last its weight at the end of the experiments, that * is, after subtracting the liquid which had vaporized and condensed on the stopper. After the end of the experiment the stopper was dried to remove the liquid, and by another weighing of the glass, together with its contents and stopper, the weight of the liquid still contained in the glass was obtained. The decrease of weight of the liquid in the glass was always found to be inconsiderable, and might without any harm have been neglected ; for the last experiment of a series I have always taken the diminished weight of the liquid into account, but for those between the first and the last I have neglected the diminution of the weight of the liquid in the glass. What I have here said explains a remark of frequent subsequent use, “ after drying the stopper.” In re- ference to the influence of the formation of vapour on the accuracy of the results obtained for the specific heat of the individual substances, compare §38. Two series of experiments in which water was contained in the glass, gave the fol- lowing results for the specific heat of this liquid : — Experiments with Glass 1. Temperature of the Air 19o,0. T T'. t\ 45*2 20-9 20-62 46-6 21-2 20-92 47-4 21-3 20-96 t. M. o grms. 16- 83 26-945 17- 03 26-935 17-03 26-965 * After drying the stopper. /• sp. H. grms. grin. 3-43 0-651 1-035 1-013 3-42* 0-997 P q 98 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. Experiments with Glass 3. Temperature of the Air 19°*0. T. T'. t'. t. M. /• X. sp. H. O 0 O o grms. grms. grm. 46*8 21*1 20*76 17*03 26*95 3*445 0*453 1*004 46*8 21*1 20*83 17*12 26*985 0*999 47*0 21*2 20*93 17*22 26*935 3*435* 55 0*996 The value found for the specific heat of the contents of the glass comes very near the number 1, assumed for the specific heat of water f. Determinations in which mercury was contained in the glass gave the following results for the specific heat of the contents of the glass. Experiments with Glass 1. Temperature of the Air 13°*8-14 °*4. T. T'. a. t. M. /• X . sp. H. o 51*1 16*8 16*50 13*41 grms. 26*945 grms. 53*015 grm. 0*651 0*0335 48*5 16*8 16*48 13*64 26*95 55 55 0*0333 45*2 16*5 16*20 13*63 26*965 55 55 0-0333 Experiments with Glass 2. Temperature of the Air 130,8-140* 4. T. T'. t'. t. M. /• X. sp. H. 50*0 O 171 16*79 13*74 grms. 26*935 grms. 60*015 grm. 0*487 0*0335 4 45*6 16*7 16*41 13*72 26*935 55 55 0*0337 The mean of these five determinations gives 0*0335 for the specific heat of mercury, in accordance with the results found by other observers for this metal (0*0330 between 0° and 100°, Dulong and Petit; 0*0333, Regnault). 26. For the liquid which is to be placed in the glass along with the substance whose spe- cific heat is to be investigated, I could in many cases use water ; but many substances, the * After drying the stopper. t In § 24 it was mentioned that the numbers obtained for the specific heat of the contents of the glass are somewhat too small, if the maximum temperature of the water in the calorimeter, t', exceeds the temperature of the air by much more than 2°. As an example I give the following determinations, in which the glass used contained water. Experiments with Glass 1. Temperature of the Air 13°-5-13°-8. T. T'. t'. t. M. /- X. sp. H. 0 0 o o grms. grms. grm. 46-5 18-1 17-81 13-64 26-94 3-40 0-651 0-976 43-9 16-7 16-38 12-33 26-955 » » 0-989 Experiments with Glass 2. Temperature of the Air 13°-5-13°*8. T. T'. t'. t. M. /• X. sp. H. t O O 0 0 grms. grms. grm. 49-1 18-3 18-03 13-37 26-94 3-66 0-487 0-981 47-6 18-3 18-04 13-66 26-99 „ „ 0-969 47-0 17*5 17-22 12-73 26-97 3-65* „ 0-991 * After drying the stopper. PEOFESSOB KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 99 determination of which is important, dissolve in. water, and hence I had to use a different liquid. Coal-tar naphtha has. the advantage that it is a mobile liquid, does not dissolve most salts, and does not resinify in contact with the air ; but besides the disagreeable odour, with continuous working, respiring air charged with its vapour appears to act injuriously on the organs of the voice. As compared with water, coal-tar naphtha has the disadvantage, that its specific heat must be specially determined, and any possible uncertainty in this is transferred to the determination of the specific heat of the solid substance ; but the thermal action of a given volume of naphtha is only about ^ that of the same volume of water*; and in experiments in which the thermal action of a solid substance is determined, along with that of the necessary quantity of liquid which is contained with that substance in a glass, the thermal action due to the solid is a larger fraction of the total if coal-tar naphtha is used than if water is the liquid, which is a favourable circumstance in the accurate determination of specific heat. As it was more especially important for me to obtain comparability in the results for specific heat, I have, for a great many substances which are insoluble in water, and for whose investi- gation water might have been used, also employed coal-tar naphtha. Water was used for a few substances which are soluble in coal-tar naphtha (sulphur, phosphorus, ses- quichloride of carbon, for instance). Several substances I determined both with water and with naphtha ; the results thus obtained agree satisfactorily. To the question as to whether any possible change in the specific heat of naphtha with the temperature can be urged against the use of this liquid, I shall return in § 29. 27. The coal-tar naphtha A which I principally used in the subsequent experiments was prepared from the commercial mixture of hydrocarbons Gn H2„_6, by purifying it by means of sulphuric acid, treating the portion which distilled between 105° and 120° with chloride of calcium for six days, then again rectifying it, and collecting separately that which passed between 105° and 120°. This liquid had the specific gravity 0-869 at 15°; in determining its specific heat I made four series of experiments, two at first when I was engaged on experiments in which I used this naphtha, and two towards the end. I. — Experiments with Glass 1. Temperature of the Air 12°T-12°-9. T. T'. f. t. M. /• X . sp. H. O o 0 o grms. grms. grm. 46-1 13-8 13-51 11-24 26-99 2-875 0-651 0-433 48-6 14-0 13-71 11-24 26-945 2-875 f 55 0-443 45-5 14-1 13-83 11-59 26-97 2-975$ 55 0-439 45-3 14-3 14-01 11-80 26-94 2-970 f 55 0-428 Mean . . . 0-436 * The specific heat of the coal-tar naphtha A, with which I made most of my experiments, is 0-431, and its specific gravity at 15°=0869. f After drying the stopper. After adding some; naphtha. 100 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. II. — Experiments with Glass 2. Temperature of the Air 12°T-12°-7. T. T'. t' t. M. /• x. sp. H. 49-0 13-8 13-53 11-02 grms. 26-955 grms. 3-28 grm. 0-487 0-438 45-9 14-1 13-83 11-50 26-93 3-48* 55 0-427 43-3 14-2 13-86 11-73 26-95 55 0-427 46-6 14-5 14-23 11-85 26-95 3-475 f 5 5 0-435 Mean 0-432 III . — Experiments with Glass 1. Temperature of the Air 16° •7. T. T'. t'. t. M. /• so. sp. H. 51°-4 18-6 18*32 16-02 grms. 26-98 grms. 2-895 grm. 0-651 0-429 51-5 18-4 18-06 15-73 26-97 „ 55 0-431 51-5 18-4 18-14 15-81 26-985 „ 55 0-431 51-0 18-5 18-22 15-93 26-96 2-88f 55 0-434 Mean 0-431 IV . — Experiments with Glass 3. Temperature of the Air 16° •7. T. T'. t'. t. M. /• X. sp. H. 0 51-7 18-7 18-43 16-22 grms. 26-935 grms. 3-195 grm. 0-453 0-423 50-7 18-6 18-32 16-14 26-935 55 „ 0-431 50-7 18-6 18-27 16-13 26-95 55 55 0-421 50-2 18-6 18-26 16-14 26-93 3-18 f 55 0-426 Mean 0-425 The average of the means of these four series of experiments, 0-436, 0-432, 0-431, 0-425, gives 0-431 as the specific heat of the coal-tar naphtha A between 14° and 52°; this value is taken in calculating the experiments in the following section. 28. If it were only a question as to the determination of the specific heat of this naphtha, the method described in the preceding might be advantageously replaced by another. For by this method the specific heat of the liquid must be found somewhat too great, owing to the fact that in the empty space in the glass under the stopper a dis- tinct quantity of vapour is formed, which condenses when the glass is dipped in the water of the calorimeter (compare § 25). Direct experiments J, in which this forma- tion of vapour was almost entirely avoided, have shown that the method used for the previous determinations, that is, the use of glasses for heating the liquid in which a * After adding some naphtha. t After drying the stopper. J I determined the specific heat of coal-tar naphtha A, using a glass in which only very little vapour could form above the heated liquid. This glass (which I used in experiments for the determination of the specific heat of liquid compounds) had a narrow neck, and was filled so that there was very little space in which vapour could form; the calorimetric value of this glass, in so far as it was immersed in the water of the PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 101 relatively considerable space above the liquid remains empty, gives the specific heat of readily vaporizable liquids somewhat too high, but that at the same time this influence of the formation and condensation of vapour is very small in the conditions under which I worked*. — The number 0-431 obtained in the previous determinations expresses the thermal action due to the cooling of 1 grm. naphtha A through 1° in my experiments, which thermal action depends to by much the greatest extent on the specific heat of this liquid, and only to a very small extent on the condensation of the previously formed vapour. In calculating the experiments communicated in the third section, that number is taken as the expression for the thermal action of naphtha, which is put as proportional to the weight of the latter. This is, strictly speaking, not accurate, in so far as the thermal action arising from condensation of vapour only depends on the magnitude of the empty space and the temperature, and not on the quantity of naphtha in the glass. But the small possible inaccuracy due to this cause in my experiments is not to be compared with other uncertainties. The manner in which I have taken into account the naphtha contained in the glass corresponds most accurately to the actual conditions of the expe- riment, when this thermal action is most considerable (only naphtha in the glass) ; and if my mode of calculation less satisfies these conditions (less naphtha in the glass), the entire amount is less considerable, and the influence of that which might be missed in that calculation, a vanishing quantity. 29. My experiments have been made at very different temperatures. The tempe- rature of the air was often something under 10°, sometimes above 20°. These numbers represent the limits to which the liquid in the glass, together with the solid substance cooled in the calorimeter. In most experiments I heated the glass with its contents to about 50°, in some cases not so high. Now, for the various intervals of temperature within which the liquid in the glass cooled, can its specific heat be assumed to be always the samel For water this may be done, and for coal-tar naphtha I did not calorimeter (comp. fig. 6), was = 0-688 grm. A series of experiments in which this glass was used to determine the specific heat of the naphtha A gave the following results : — Temperature of the Air 15°-5- -15°-6. T. T'. t'. t. M. f. X. sp. H. O Q O grms. grms. grm. 52-5 17-8 17-53 14-93 26-945 3-205 0-688 0-415 49-6 17-4 17-13 14-73 26-955 „ „ 0-412 50-9 17-6 17-29 14-83 26-96 „ „ 0-407 50-5 17-6 17-26 14-83 26-975 „ „ 0-407 51-6 17-7 17-38 14-84 26-985 „ „ 0-416 50-9 17-8 17-47 15-03 26-94 „ „ 0-405 Mean . . . 0-410 * This is seen from the experiments on water communicated in § 25, and from the subsequent determinations in the next section, in which water was contained in the glass along with the solid substance. 102 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. doubt it while engaged in my experiments. I first, when they were finished, became acquainted with Regnault’s * investigations on the specific heat of liquids at various temperatures; according to these experiments the specific heat of some liquids con-, siderably increases with the temperature. I have not directly investigated coal-tar naphtha in this respect, but it is probable that the specific heat of this mixture of hydrocarbons Gn H2 n_6, alters but little with the temperature, and it is certain that this change is without influence on the accuracy of my determinations of the specific heats of solid substances. Regnault’s experiments f , made by the method of cooling, show no change for benzole, €e He, between 20° and 5°, while there is a distinct change in the case of alcohol. For pure benzole % I found the specific heat by the method of mix> ture to be 0-450 between 46° and 19°; Regnault § found it between 71° and 21° to be 0-436. These numbers, obtained with different preparations, are not indeed com- parable for a decision of the question just discussed, but they render improbable a com siderable increase in the specific heat of benzole with the temperature. What I more especially lay weight upon is this : the specific heats of solids which I have determined at various temperatures, by their agreement with the numbers previously found by others, do not indicate any influence of a change of specific heat of naphtha with the temperature. 30. My stock of the naphtha, discussed in § 27, was used before I had investigated all the solid substances, for which a determination of the specific heat appeared necessary. Another quantity of the same coal-tar naphtha was subjected to the same treatment as indicated there, and the portion passing over between 105° and 120° used for the remainder of the experiments. To ascertain the specific heat of this naphtha B, I made the four following series of experiments : — I. — Experiments with Glass 1. Temperature of the Air 18°-l-18°-3. T. T'. i. t. M. /• X. sp. H. O O 0 0 grms. grms. g™. 51-5 19-6 9-33 17-22 26-96 2-70 0-651 0-419 52-7 19-9 19-64 17-49 26-95 59 55 0-413 50-5 19-8 19-54 17-51 26-99 0-420 49-9 20-0 19-73 17-75 26-995 2-695 || 59 0-422 Mean . . . 0-418 * Relation des experiences .... pour determiner les lois et les donnees physiques necessaires au calcul des machines a feu, vol. ii. p. 262 (1862). t Ann. de Chim. et de Phys. [3] vol. ix. pp. 336 & 349. £ Poggendorff’s ‘ Annalen,’ vol. lxxv. p. 107. § Relation, etc vol. ii. p. 283. || After drying the stopper. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 103 II. — Experiments with Glass 3. Temperature of the Air 18°T-18°-3. T. T'. t\ t. M. /. X. sp. H. 51-4 19-7 19-36 17-32 grins. 26-94 grms. 3-085 grm. 0-453 0-415 51-5 19 9 19-63 17-56 26-965 55 0-426 49-1 19-9 19-61 17-73 26-955 55 « 0-416 50-5 20-1 19-82 17-86 . 26-98 3*08 * 0-418 Mean • - - 0-419 III.- —Experiments with Glass 1. Temperature of the Air 17°-8-18°-3. T. T'. t'. t. M. /• X. sp. H. 52-2 19-8 19-49 17-27 grms. 26-97 grms. 2-80 grm. 0-651 0-427 50-6 20-0 19-73 17-64 26-96 59 „ 0-425 51-2 20-2 19-92 17 82 26-98 55 0-420 51-3 20-2 19-86 17-76 26-99 95 ?? 0-418 50-4 20-2 19-86 17-85 26-95 2-785 * 55 0-410 Mean 0-420 IV. — Experiments with Glass 3. Temperature of the Air 18° ■4. . T. T'. t'. t. M. /• X. sp. H. 50-2 19-7 19-43 17-33 grms. 26-96 grms. 3-31 grm. 0-453 0-424 50-1 20-1 19-77 17-66 26-99 55 95 0-416 52-5 20-2 19-87 17-65 26-96 55 59 0-423 50-1 20-1 19-83 17-82 26-95 55 55 0-409 51-4 20-2 19-93 17-82 26-97 3-29 * 55 0-417 Mean 0-418 The average of the means of these four series of experiments, 0-418, 0-419, 0*420, 0-418, gives 0-419 for the specific heat of coal-tar naphtha B between 20° and 50°. In the preceding method of experiment, whether water or naphtha of the kind described is contained in the vessel, a temperature much higher than 50° cannot be employed; for otherwise the quantity of liquid evaporating and condensing on the stopper becomes far too considerable. Perhaps with hydrocarbons of higher boiling- points higher temperatures might be ventured upon: I have no experiments on this subject. PART III.— DETERMINATION OF THE SPECIFIC HEAT OF INDIVIDUAL SOLID SUBSTANCES. 31. By the method whose principle and mode of execution have been discussed in the preceding, I have determined the specific heat of a large number of solid substances. I * After drying the stopper. MDCCCLXV. Q 104 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. should have liked to include a still larger number of bodies in my investigations ; but a limit was put by the straining of the eyes from constant reading of finely divided scales, and by the injurious action which the long-continued working with coal-tar naphtha produces. My crystallographic collection furnished me with much material for investigating the specific heat of both naturally occurring and artificially prepared substances, but for much more I have to thank others. By far the greater part of the chemical prepara- tions investigated ! obtained from the Laboratory of the University of Giessen, through the kindness of the Director, Professor Will, and of the assistants, Professor Engelbach, to whom my thanks are especially due, Drs. Korner and Dehn. Professor Wohler, of Gottingen, placed a number of chemical preparations at my disposal. Professor Bunsen, of Heidelberg, has helped me to the investigation of some rubidium-com- pounds. Platinum and iridium I have been furnished with by M. Her^eus, the pro- prietor of the well-known platinum-manufactory in Hanau. I have had a very large number of minerals from the mineral collection of the University of Giessen, through the kindness of the Director, Professor Knop; and to obtain the necessary quantity of dioptase, Professors Blum of Heidelberg, and Dunker of Marburg, have contributed. 32. The signification of the letters in the statement of the following experiments and their calculation is clear from § 17 ; in reference to the value of the numbers for M, compare § 21, for x § 22, for T' § 23, for y § 27 and § 30. It would require too much space always to give the comparison of my results with those of other observers. I can only do this in individual cases where there are con- siderable differences and their discussion is of importance. For other substances, where there are recent observations by trustworthy observers, the Tables in § 82 to § 89 give data for comparison. 33. Sulphur: pieces of transparent (rhombic) crystals from Girgenti. I made three series of experiments with this substance. I.— Experiments with Water. Glass 1. Temperature of the Air 13°-2. T. O T'. O t'. o t. M. grms. m. grms. /• grm. y* sc. grm. sp. H. 45-8 15-5 15-24 11-74 26-95 4-16 1-765 1-000 0-651 0-168 46*0 16-2 15-93 12-52 26-935 55 55 55 55 0-160 45-2 16-0 15-73 12-42 26-945 55 55 55 0-153 45-8 16-4 16-05 12-74 26-96 55 1-75* 55 Mean 55 0-153 0-159 * After drying the stopper : compare § 25. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 105 II. — Experiments with Water. Glass 2. Temperature of the Air 13°*2. T. T'. t'. t. M. m. /• y- X. sp. H. O O 0 0 grins. grms. grms. grin. 45*8 16*4 16*07 12*36 26*96 4*815 2*09 1*000 0*487 0*171 47*3 16*6 16*33 12*46 26*95 33 55 5? 33 0*170 44*1 16*5 16*15 12*74 26*925 33 99 55 33 0*156 45*1 16*6 16*28 12*77 26*96 33 2*07* „ Mean 33 0*159 0*164 Both these series of determinations are from the time when I first worked at this subject. Towards the end, when I had acquired tolerable readiness, I made a third series, which agreed very closely with the results previously obtained. III. — -Experiments with Water. Glass 3. Temperature of the Air 17°*2. T. T. o t'. 0 t. o M. grms. m. grms. /• grms. y- CC. grm. sp. H. 43*7 19*1 18*83 15*79 26*99 4*92 2*065 1*000 0*453 0*166 43*5 19*1 18*84 15*84 26*97 33 33 33 33 0*162 43*3 19*2 18*92 15*92 26*94 33 33 33 0*170 43*1 19*2 18*87 15*93 26*98 33 2*05 * 33 Mean 33 0*166 0*166 Taking the mean of the means obtained in the three series of experiments, 0T59, 0T64, 0T66, we obtain 0T63 as the specific heat of rhombic sulphur between 17° and 45°. By the method of cooling, Dulong and Petit found the specific heat of sulphur at the mean temperature to be 0T88 ; Neumann found 0*209 by the method of mixture; for sulphur which had been purified by distillation, fused and cast in rolls, Begnault found f the specific heat between 14° and 98° to be 0*2026. In these expe- riments a development of heat depending on a change from amorphous sulphur into rhombic-crystallized appears to have cooperated, and to have caused the circumstance observed by Begnault, that after immersing the heated sulphur in the water of the calorimeter, the maximum temperature was only set up after an unusually long time. Sulphur which has solidified after being melted, usually contains an admixture of amorphous sulphur, the greater the more the melting-point has been exceeded, which at the ordinary temperature passes slowly, at 100° more rapidly, into crystallized, accom- panied by disengagement of heat. The transformation of the sulphur set up by the heating, and continued in the water of the calorimeter, brought about this slow appear- ance of the maximum temperature, and made the specific heat appear too great ; for Begnault’s subsequent determinations J, also made between 97° and 99° and the mean temperature, gave it considerably less: 0*1844 for freshly melted sulphur (in which * After drying the stopper. t Ann. de China. et de Phys. [2] vol. lxxiii. p. 50. Ibid. [3] vol. ix. pp. 326 & 344. Q 2 106 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. superfusion had been avoided P) ; 0-1803 for sulphur which had been melted two months ; 0*1764 for what had been melted two years (and which had then given 0-2026) ; 0-1796 for sulphur of natural occurrence. The difference between the latter result and my own doubtless depends, partially at least, on the fact that Regnault’s determination was made between 14° and 99° (the latter of which temperatures is very near the melting- point of rhombic sulphur) ; mine was made between 17° and 45° *. Tellurium : crystalline pieces f . Experiments with Naphtha A. Glass 3. Temperature of the Air 18 °*6-19°v T. T'. t'. t. M. m. /• y- ■ X. sp. H. o o o o grms. grms. grm. grm. 51-8 20-4 20-07 17-96 26-93 10-80 1-93 0-431 0-453 0-0486 51-3 20-3 20-02 17-93 26-98 35 33 33 0-0495 51-5 20-7 20-36 18-33 26-93 33 33 „ 0-0454 51-0 20-7 20-43 18-43 26-955 „ 1-91$ 33 0-0466 Mean 0-0475 34. Boron. — I have made some experiments with this substance, which have some interest for the question whether this body has essentially different specific heats in its different modifications ; but the results are not very trustworthy, owing to the spongy nature of the amorphous boron and the doubtful purity of the crystallized variety. The amorphous Boron § which I investigated was pressed in small bars, and had stood several days in vacuo over sulphuric acid. Experiments with Naphtha A. Glass 1. Temperature of the Air 17o"0-17o-2. T. o T'. o o t. o M. grms. m. grm. /• grms. y- X . grm. sp. H. 49-0 18-7 18-73 16-36 26-955 1-52 2-515 0-431 0-651 0-246 48-1 18-6 18-55 16-23 26-965 99 99 99 99 0-254 48-0 18-6 18-64 16-33 26-95 99 99 99 99 0-252 47-9 18-7 18-72 16-42 26-95 99 2*49 J 99 Mean 99 0-262 0-254 Even if the results of the individual experiments agree tolerably with each other they are not very trustworthy ; for the quantity of boron (only 1^ grm.) is very small, and the amount of heat due to the boron is a very small part of the total (comp. § 19). Yet I do not consider the result of the above series of experiments (that between 18° and 48° the specific heat of amorphous boron is about 0-254) as being very far from * There is nothing known certainly as to whether the different modifications of sulphur have essentially different specific heats. Marchand and Scheerer’s experiments on brown and yellow sulphur made by the method of cooling, compare in Journal fiir Prakt. Chemie, vol. xxiv. p. 153. f “ Obtained from Yienna, and obviously distilled.” — Wohler. + After drying the stopper. § “ Prepared from boracic acid by sodium, and treated with hydrochloric acid.” — Wohler. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 107 the truth. There are no considerable accidental errors of observation in these experi- ments, to judge from their agreement with one another. Of the constants for calcu- lating the experiments, x and y must be taken into account in regard to any possible uncertainty. It has been assumed that #=0‘615 and ^=0-431 ; if we took #=0*63 and y=0*41, the specific heat as the mean of four experiments would be =0*30 ; if x were 0-67 and y 0*45, the specific heat would be 0*21. But from what has been com- municated in § 22 and § 27 in reference to the determination of x and y, it cannot be assumed that any possible uncertainty in reference to these values can reach either of the above limits. It can be assumed with the greater certainty that the specific heat of amorphous boron is between 0*2 and 03 and nearly 0*25, because x and y could not simultaneously both be found too great or too small (if x had been too small y would have been too great, and vice versd). Crystallized Boron *. Experiments with Naphtha A. Glass 3. Temperature of the Air 18°*9-18°*7. T. T'. t'. t. M. m. /• y- X. sp. H. O 0 0 o grms. grms. gnn. grm. 50*9 20*8 20*52 18*53 26*94 2*82 1*53 0*431 0*453 0*237 51*3 20*8 20*52 18*52 26*975 55 55 55 55 0*233 51*5 20*8 20*53 18*53 26*985 n 55 55 55 0*229 51*4 20*8 20*46 18*43 26*99 55 l*52f „ Mean 55 0*222 0*230 Hence the specific heat of the crystallized (adamantine) boron investigated is 0*230 between 21° and 51°; it is pretty near that found for amorphous boron, 0*254. Reg- nattlt found J (between 98° and 100° and the mean temperature) 0*225 for a specimen of crystallized boron prepared by Rousseau; 0*257 for one prepared by Debray; 0*262 for one obtained from Deville; and 0*235 for a specimen of graphitic boron prepared by Debray. The specific heat of amorphous boron could not be determined by Reg- nault’s method, because, when heated to 100° in air, it partially oxidizes into boracic acid with disengagement of heat (three experiments, in which the quantity of boracic acid formed was determined, and its specific heat, but not the thermal action due to the forma- tion of hydrated boracic acid in immersion in water allowed for, gave respectively 0*405, 0*348, and 0*360, which numbers Regnault does not consider as even approximately re- presenting the specific heat of amorphous boron), and when greatly cooled disengages a quantity of air when immersed in warmer water, which renders the results uncertain. * “Made in Paris, probably by Rousseau, and doubtless by melting borax with aluminium. To conclude from its external appearance, it probably contained some aluminium and carbon : compare the analysis in Ann. der Chem. und Pharm. vol. ci. p. 347.” — Wohlek. t After drying tbe stopper. + Ann. de Chim. et de Pbys. [3] vol. lxiii. p. 31. 108 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 35. Phosphorus. — I have only made a few determinations with ordinary yellow phos- phorus, which was cast in sticks. Experiments with Water. Glass 1. Temperature of the Air 10o,9. T. T'. t'. t. M. m. /• y- X m sp. H. O o 0 o grms. grms. grms. grm. 38-8 13-5 13-20 10-05 26-95 3-075 2-065 1-000 0-651 0-208 33-8 12-9 12-62 10-03 26-97 „ „ ,, 55 0-204 35-5 13-2 12-91 10-17 26-93 55 2-06* J? 55 0-195 Mean 0-202 The specific heat of yellow phosphorus, as deduced from these determinations, is somewhat greater than that found by Regnault, doubtless because in my experiments the upper limit of temperature, T', was nearer the melting-point of phosphorus, 44°. Compare § 82. Antimony. — Purified by Liebig’s method ; crystalline pieces. I. — Experiments with Naphtha A. Glass 2. Temperature of the Air 14°-7. T. T'. t'. t. M. m. /• y- X. sp. H. o O o 0 o grms. grm. grm. 46-4 16-0 15-65 13-42 26-945 12-245 1-925 0-431 0-487 0-0539 44-9 15-9 15-64 13-54 26-98 5> 55 55 55 % 0-0520 44-2 15-8 15-53 13-52 26-96 55 1-91* „ Mean '55 0-0496 0-0518 II. — Experiments with Water. Glass 1. Temperature of the Air 15° •8-16°-l. T. T'. t\ t. M. m. /• y- X . sp. H. 0 o o o grms. grms. grms. grm. 45-0 17-9 17-60 14-22 26-945 11-835 2-095 1-000 0-651 0-0519 45-1 17-9 17-64 14-25 26-96 55 55 55 55 0-0519 45-0 17-9 17-64 14-25 26-965 55 55 55 55 0-0530 45-4 18-1 17-76 14-34 26-955 ” 2-085* „ Mean 51 0-0542 0-0528 From these determinations, the average of the means of both series of determinations, 0-0518 and 0-0528, the number 0-0523 is the specific heat of antimony between 17° and 45°. Bismuth. — Purified by melting with nitre, and cast in small bars. In the case of this metal also, I have made a series of determinations with coal-tar naphtha in the glass, and one with water. After drying the stopper. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 109 I. — Experiments with Naphtha A. Glass 3. Temperature of the Air 180,9-180,8. T. 50-8 T'. 20-6 t'. . 20-33 t. 18-33 M. grms. 26-99 m. grms. 20-71 /• grm. 1-70 y- 0-431 x. sp. H. grm. 0-453 0-0291 50-3 20-7 20-42 18-43 26-955 99 99 „ „ 0-0302 50-1 20-6 20-33 18-37 26-955 99 99 99 0-0292 50-9 20-7 20-40 18-42 26-955 99 1-685 * 99 „ 0-0284 Mean . . . 0-0292 II. — Experiments with Water. Glass 1. Temperature of the Air 16°-7-16°-8. T. 45-2 T'. 18? 7 t'. 18-44 . t. 15-25 M. grms. 26-97 m. grms. 19-43 /- grm. 1-995 1-000 x. sp. H. grm. 0-651 0-0309 45-5 18-9 18-57 15-36 26-965. 99 „ 99 ,. 0-0313 45-0 18-9 18-64 15-47 26-975 99 99 99 „ 0-0324 46-0 181 18-82 15-56 26-99 99 1-985* 99 Mean . „ 0-0327 . . 0-0318 From these determinations we get for the specific heat of bismuth between 30° and 48° the number 0-0305. 36. Carbon. — It is known how different are the numbers obtained for the specific heat of carbon in its different forms. I have determined the specific heat for comparatively only a few of the modifications of carbon — for gas-carbon, for natural and artificial gra- phite. Before the experiment each of these substances was strongly heated for some time in a covered porcelain crucible, and then allowed to cool, and immediately trans- ferred into the glass for its reception, and, after weighing, naphtha poured over it. Gas-carbon from a Paris gas-works ; very dense, of an iron-grey colour, and left very little ash when calcinedf. It was used in pieces the size of a pea, and two series of experiments were made. * After drying the stopper. t This carbon, as well as the above-mentioned varieties of graphite, was analyzed in the Laboratory at Giessen by Mr. Hubek. The gas-carbon gave, when placed in a platinum boat and burned in a stream of oxygen,— I. II. III. IV. V. Carbon . . 97-19 98-25 97-73 98-08 98-55 Hydrogen . '. . . 0-53 0-15 0-68 0-37 1-00 Ash . . 0-61 0-62 0-73 0-23 0-69 98-33 99-02 99-14 98-68 100-24 110 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. I. Experiments with Naphtha A. Glass 1. Temperature of the Air 18o,9-190,2. T. T'. t'. t. M. m. /• y • X. sp. H. O O o 0 grms. grms. grm. grm. 52*9 20*8 20*53 18*13 26*955 3*135 1*825 0*431 0*651 0*184 52*6 20*9 20*63 18*26 26*98 „ 33 „ 0*185 51*7 20*7 20*42 18*06 26*97 33 35 33 „ 0*196 52*4 20*9 20*58 18*23 26*98 33 1*805* 33 J? 0*186 Mean . . . 0T88 II. — Experiments with Naphtha A. Glass 3. Temperature of the Air 20°*5-20°*8. T. T'. t' t. M. m. /• y- X. sp. H. 52*6 22*6 22*33 20*23 grms. 26*985 grms. 3*345 grm. 1*935 0*431 grm. 0*453 0*180 52*2 22*5 22*23 20*14 26*985 33 33 33 33 0*183 52*3 22*5 22*20 20*12 26*965 33 33 33 33 0*179 52*5 22*6 22*31 20*22 26*955 1*91* 33 33 0*182 Mean . . . 0*181 These determinations give as the average of the means of both sets of experiments the number 0*185 as the specific heat of gas-carbon between 22° and 52°. Natural graphite from Ceylon. Left very small quantities of ash when calcinedf. I. — Experiments with Naphtha A. Glass 3. Temperature of the Air 18°*9-19°*2. T. T'. t'. t. M. o o o 0 grms. 51*4 20*8 20*48 18*13 26*975 51*4 20*8 20*51 18*13 26*99 51*8 20*8 20*54 18*15 26*975 52*0 20*8 20*54 18*13 26*99 * After drying the stopper, t In Mr. Hubeb’s analyses this substance was m. /• y- X . sp. H. grms. grms. grm. 4*025 2*085 0*431 0-453 0*179 55 33 0*186 „ ?5 33 0*181 „ 2*06* „ 33 0*183 Mean 0*183 in a platinum boat, then burned in a porcelain tube in oxygen. I. II III. Carbon 99-11 98-52 Hydrogen . . 0-17 0-06 Ash . . 0-26 0-27 0-51 99-55 99-09 The residual porous ash left after the combustion was tolerably white, with admixed red particles. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. Ill II. — Experiments with Naphtha A. Glass 1. Temperature of the Air 19°-0-18°*7. T. T'. t\ t. M. m. /• y- X. sp. H. 0 o grms. grms. gnu. grm. 53-9 21-1 20-77 18-22 26-97 3-515 1-935 0-431 0-651 0-174 52-2 21-0 20-73 18-31 26-96 55 55 » „ 0-176 52*1 21*2 20-86 18-52 26-94 „ 0-158 53-0 21-0 20-73 18-32 26-97 „ 55 „ „ 0-155 52-8 21-0 20-73 18-33 26-965 55 1-91* „ „ 0-160 Mean 0-165 III. — Experiments with Naphtha A. Glass 3. Temperature of 1 the Air ■ 19°-9-20°-0. T. T'. t'. t. M. m. /- y- X . sp. H. 0 o o o grms. grms. grms. grm. 51-6 21*9 21-55 19-33 26-97 3-90 2-05 0-431 0-453 0-174 51-3 22-0 21-71 19-52 26-955 55 55 0-174 51-5 22-0 21-70 19-52 26‘97 55 55 0-168 51-5 21-9 21-63 19-42 26-96 5J 2-04* 55 55 0-175 Mean . . . 0T73 The average of the means of these three series of determinations, 0T83, 0T65, and 0T73, gives 0T74 as the specific heat of Ceylon graphite between 21° and 52°. Iron graphite from Oberhammer, near Sayn, separated upon black ordnance iron. Thin, very lustrous laminae, freed from iron by treatment with aqua regia as much as possible, yet not completely f. * After drying the stopper. t This iron graphite, according to Mr. Huber’s analyses, in which it was also burned in oxygen in a plati= i num boat placed in a porcelain tube, gave the following results : — • I. II. III. Carbon . . 97-01 96-12 96-37 Hydrogen . . 0-12 0-18 Ash . . 4-88 C» 3-99 101-89 101-11 100-54 It is probable that both in this graphite and in that of natural occurrence, the hydrogen is not essential, but arises from hygroscopic moisture. The residual ash contained porous particles consisting of sesquioxide of iron and silica, and also small pellets, covered externally with a layer of magnetic oxide of iron : these dissolved in hydrochloric acid at first quietly, and afterwards under disengagement of hydrogen ; and in the solution small blisters of graphite could he perceived. It is owing to the oxidation of the iron that the sum of the constituents in all cases exceeds 100. R MDCCCLXV. 112 PEOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. I. Experiments with Naphtha A. Glass 3. Temperature of the Air 19o-0-18°-7. T. T'. t'. t. M. m. /• y ■ ■ X, sp.H. O grins. grms. grms. grm. 52-5 20-8 20-53 18-21 26-955 2-51 2-445 0-431 0-453 0-186 52-9 21-1 20-84 18-54 26-98 55 2-565* 55 55 0-156 51-4 20-9 2064 18-43 26-94 „ 55 ,, „ 0-157 52-0 20-9 20-60 18-33 26-99 55 2-545f „ 55 0-168 Mean 0-167 .—Experiments with Naphtha A. Glass 1. Temperature of the Air 19°-9-20°-0. T. T'. t'. t. M. ra. /• y- oc. sp. H. o O 0 o grms. grms. grms. grm. 52-1 21-9 21-57 19-32 26-94 2-48 2-205 0-431 0-651 0-164 51-7 22-0 21-66 19-45 26-97 55 55 55 55 0-163 51-5 22-0 21-73 19-54 26-98 55 55 „ 0-162 51-5 22-0 21-66 19‘46 26-945 55 2-19f 55 55 0*167 Mean . 0T64 The average of the means of both these series of experiments, 0T67 and 0T64, gives 0T66 as the specific heat of iron graphite between 22° and 52°. The results previously known in reference to the specific heat of carbon, differ greatly for its different conditions, as also do the results obtained by different inquirers and by different methods for the same condition. But even leaving out of consideration the numbers obtained by De la Rive and Marcet by the method of cooling, there are still considerable differences between Regnault’s results, obtained by the method of mixture, and my own. Regnault found for animal charcoal 0-261, for wood-charcoal 0-241, for gas-carbon 0-209, for natural graphite 0-202, for iron graphite 0*197, for diamond 0-1469 ; his experiments gave greater numbers for the same substance than my own. I think that exactly for a substance like carbon in its less dense modifications, my method promises more accurate results than that of Regnault. Even in mine, the substance, after being strongly heated before the experiment, might absorb gases or aqueous vapour, which would make the specific heat too great. But in Regnault’s method this source of error might also operate, and more especially also the source of error due to the disengage- ment of heat when porous substances are moistened by water. These sources of error, which affect the determination of the specific heat of the various modifications of carbon and make it too high, have the more influence the looser and the more porous the sub- stance investigated. I believe that the only certain determination of the specific heat of carbon is that of diamond, and all other determinations are too high, owing to various circumstances, and in Regnault’s experiments with wood and animal charcoal, &c., owing to the heat disengaged when these substances are moistened by water. * After some more naphtha had been added. t After drying the stopper. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 113 37. Silicium. — I have investigated this substance in four different modifications. Amorphous Silicium *. — For the experiments picked coherent pieces were used, which had stood for several days in vacuo over sulphuric acid. Experiments with Naphtha A. Glass 3. Temperature of the Air 19°-2. T. T'. t'. t. M. m. /• V' X. sp. H. 0 grms. grm. grms. grm. 0-251 5l-5 20-7 20-38 18-13 26-95 1-095 2-88 0-431 0-453 50-0 20-8 20-54 18-46 26-975 55 „ 99 99 0-208 50-4 21-0 20-66 18-55 26-98 „ ,, 99 99 0-221 50-5 20-9 20-59 18-52 26-935 „ 2-87f „ 99 0-177 Mean . . . 0-214 The very discordant results of these experiments are very little trustworthy ; the quantity of silicium, 1 grm., was too small, and its thermal action inconsiderable as com- pared with that of the other substances immersed with it in the water of the calorimeter. Graphitoidal Silicium J. Experiments with Naphtha A. Glass 3. Temperature of the Air 16°-7-17°-2. T. T'. a. t. M. m. /• y- x. sp. H. O o o o grms. grms. grm. grm. 51-0 18-8 18-51 16-34 26-965 3-155 1-83 0-431 0-453 0-182 52-3 19-1 18-82 16-59 26-975 99 99 99 „ 0-181 51-1 18-9 18-62 16-44 26-98 99 99 99 „ 0-185 50-4 18-8 18-52 16-43 26-95 l-81f 99 „ 0-174 Mean . . . 0-181 Crystallized Silicium . — Grey needles §. Experiments with Naphtha A. Glass 1. Temperature of the Air 19°-1. T. O T'. o t'. 0 t. o M. grms. m. grms. /• grm. y- X. grm. sp. H. 53-8 21-1 20-83 18-53 26-94 2-395 1-955 0-431 0-651 0-168 52-6 21-0 20-74 18-52 26-975 99 99 99 ,5 0-168 52-3 21-0 20-72 18-52 26-98 99 99 99 55 0-168 51-9 21-0 20-66 18-53 26-975 99 l-935f Mean 55 0-156 0-165 * “ Prepared from silicofluoride of potassium by means of sodium.” — Wohler. t After drying the stopper. + “ Obtained by melting silicofluoride of potassium, or sodium, with aluminium ; the aluminium was then extracted with hot hydrochloric acid, and the oxide of silicium with fluoric acid.” — Wohler. § “ This silicium was prepared from the silicofluoride of potassium, or sodium, by sodium and zinc, and the lead (from the zinc) removed by nitric acid. Whether it was afterwards treated with hydrofluoric acid 1 cannot say, but probably so. It was quite unchanged when heated in the vapour of hydrochlorate of chloride of silicium (passed by means of hydrogen). Probably it contained, however, like all silicium reduced by zinc, a trace of iron, which appears when it is heated in chlorine. An experiment with another portion of such silicium gave, however, so little iron that its quantity could not be determined.” — Wohler. R 114 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. Fused Silicium *. Experiments with Naphtha A. Glass 1. Temperature of the Air 18°*9-180,7. T. T'. t'. t. M. m. /• y- a?. sp. H. Q grms. grms. grm. grm. 0-142 49-0 20-5 20-24 18-40 26-97 417 1-555 0-431 0-651 50-5 20*7 20-43 18-52 26-96 99 55 0139 49-7 20-6 20-27 18-42 26-965 99 55 55 55 0136 50-8 20-7 20-43 18-52 26.94 99 l-145f „ 55 0136 Mean . . . 0138 38. Tin : reduced from the oxide, cast in small bars. I. — Experiments with Naphtha A. Glass 1. Temperature of the Air 17°-8-180,8. T. T'. t'. t. M. m. /• y- CO. sp. H. 0 0 grms. grms. grm. grm. 51-4 19-8 19-46 1714 26-965 14-835 1-385 0-431 0-651 0-0493 51-4 19-9 19-62 17-23 26-98 99 99 99 99 0-0539 51-3 20-0 19-72 17-34 26-95 99 99 99 0-0540 51-5 20-3 20-03 17-65 26-995 99 1-365 f „ 99 0-0553 Mean 0-0531 11. — Experiments with Water. Glass 1. Temperature of the Air 15' 3-5-15°-9. T. T'. t'. t. M. m. /• y- X. sp. H. o 0 o o grms. grms. grm. grm. 45-1 17-5 17-24 14-13 26-975 14-62 1-595 1-000 0-651 0-0543 46-4 17-5 17-24 13-94 26-985 99 99 99 99 0-0571 45-6 17-6 17-34 1414 26-99 99 99 99 99 0-0574 45-7 17-6 17-34 1414 26-95 99 1-58 f 99 99 0-0573 Mean 0-0565 The average of the means of these two series of observations gives 0-0548 as the specific heat of tin between 19° and 48° at 0-0548. Platinum : several pieces of fused platinum and of thick platinum wire. Experiments with Naphtha A. Glass 1. Temperature of the Air 170,8-18°-2. T. T’. t'. t. M. m. /• y • X . sp. H. 53-5 20-4 20-14 17-23 grms. 26-96 grms. 23-625 grm. 2-225 0-431 grm. 0-651 0-0322 52-8 20-0 19-65 16-73 26-975 99 99 99 99 0-0335 51-5 20-0 19-73 16-95 26-96 99 99 99 0-0326 50-9 20-0 19-74 17-05 26-96 „ 2-205 f 99 99 0-0316 I have also made a few experiments with a piece of fused iridium which M. Herjsus gave me. "Wohler had obtained it from Detille ; it formed a cylindrical piece. After drying the stopper. PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 115 Experiments with Naphtha A. Glass 3. Temperature of the Air 170,8-18°-2. T. T'. t'. t. M. m. /• y- X . sp. H. O o o o grms. grms. grms. grm. 51-8 19-5 19.24 16-93 26-995 16-66 2-04 0-431 0-453 0-0359 51-0 19-6 19-26 16-95 26-97 55 95 59 55 0-03911 50-0 19-5 19-24 17-06 26-965 59 55 55 59 0-0357 50-5 19-6 19-34 17-13 26-93 „ 2-03 * 0-0359 Excluding • the second experiment, which is obviously uncertain, these determinations give 0-0358 as the specific heat of iridium. This iridium was not free from metals of smaller atomic weight and greater specific heat. For various specimens of impure iridium, Regnault (Ann. de Chim. et de Phys. [2] vol. lxxiii. p. 53; [3] vol. xlvi. p. 263 ; vol. lxiii. p. 16) found 0-0368, 0-0363, 0-0419, and for almost pure iridium 0-0326. 39. Silver : pure, cast in bars. Experiments with Naphtha A. Glass 3. Temperature of the Air 18°-9-19°T. T. T'. t'. t. M. m. /• y- X. sp. H. o O o o grms. grms. grm. grm. 52-1 21-1 20-82 18-15 26-975 21-51 1-585 0-431 0-453 0-0552 51-5 21-1 20-77 18-14 26-99 55 55 55 55 0-0557 51-4 20-9 20-62 17-94 26-98 55 55 95 „ 0-0574 50-9 21-0 20-65 18-06 26-95 55 59 55 „ 0-0557 51-0 21-1 20-83 18-25 26-965 59 1-565* „ 55 0-0558 Copper. — Commercial copper wires f . I. — Experiment with Naphtha A. Glass 1. Mean Temperature . . . 0-0560 of the Air 13°-2. T. T'. t\ t. M. m. /• y ■ X . sp. H. o 0 0 0 grms. grms. grm. grm. 44-3 15-9 15-64 12-64 26-985 16-505 1-675 0-43] . 0-651 0-0895 46-2 15-1 14-82 11-43 26-97 „ 55 55 „ 0-0949 45-7 15-2 14-91 11-63 26-97 55 55 55 55 0-0926 47-7 15-2 14-93 11-43 26-98 „ 1-67* „ „ 0-0930 * After drying the stopper, t With reference to what has been said in § 24, I Mean here communicate a series . . . 0-0925 of experiments (one o earliest) where t' was much more above the temperature of the air than usual, and hence too small numbers were obtained for the specific heat of the substance in question. Experiments with Naphtha A. Glass 2. Temperature 130-8. T. T'. t'. t. M. m. /. y> X. sp. H. 45-6. 16-5 16-23 13-02 grms. 26-98 grms. 18-33 grm. 1-96 0*431 grm. 0*487 0-0897 48-5 16-9 16-64 13-21 26-97 99 0-0870 43-7 16-5 16-15 13-21 26-98 99 1-95* 0-0867 * After drying the stopper. 116 PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. II. — Experiments with Naphtha B. Glass 3. Temperature of the Air 19°‘4-19o,0. T. T'. t'. t. M. TO. /• y- X. sp. H. grms. grms. grm. grm. 55-0 21-9 21-62 18-06 26-96 19-725 1-56 0-419 0-453 0-0909 54-1 21-4 21T1 17-60 26-965 55 55 55 55 0-0906 53-6 21-2 20-86 17-36 26-99 55 55 55 55 0-0917 54-2 21-3 20-96 17-44 26-98 55 55 55 0-0902 51-7 21-2 20-85 17-55 26-965 ” 1-545 * „ Mean 55 0-0921 0-0911 hi.—: Experiments with Water. Glass 1. Temperature of the Air 18! o* OO i — 1 1 T. T'. t'. t. M. TO. /• y- OB. sp. H. 0 O 0 o grms. grms. grm. grm. 49-7 20-8 20-50 16-17 26-95 18-26 1-625 1-000 0-651 0-0965 50-0 20-6 20-32 15-93 26-96 55 55 0-0958 49-5 20-8 20-50 16-22 26-93 55 „ 0-0953 47-9 20-9 20-62 16-64 26-945 55 1-615 * „ Mean 55 0-0934 0-0953 According to these determinations, the mean of the average results 0-0925, 0-0911, 0-0953, the number 0-093 represents the specific heat of copper between 20° and 50°. 40. Lead : reduced from sulphate of lead and cast in small bars. I. — Experiments with Naphtha A. Glass 1. Temperature of the Air 18°-9-18°-8. T. T'. t'. t. M. TO. /• y- X. sp. H. O O o o grms. grms. grm. grm. 50-5 20-6 20-33 18-23 26-995 19-93 1-465 0-431 0-651 0-0308 50-5 20-7 20-43 18-35 26-975 55 55 55 „ 0-0302 50-9 20-7 20-44 18-35 26-965 55 55 55 55 0-0293 50-5 20-6 20-32 18-24 26-94 55 1-445 * 55 0-0302 Mean , . . 0-0301 II. — Experiments with Water. Glass 1. Temperature of the Air 15°-5-150,9, T. T'. t'. t. M. TO. /• y- X . sp. H. 46-0 o 17-5 17-21 14-02 grms. 26-96 grms. 24-845 grm. 1-56 1-000 grm. 0-651 0-0325 45-3 17-6 17-32 14-23 26-985 55 55 55 0-0322 45-9 17-7 17-42 14-25 26-945 55 55 55 55 0-0329 46-1 17-9 17-61 14-43 26-985 „ 1-55 * 55 55 0-0339 Mean . . . 0-0329 The mean of the averages of both series of experiments, 0-0301 and 0-0329, gives for the specific heat of lead between 19° and 48° the number 0-0315 * After drying the stopper, PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 117 Zinc : purified, cast in small bars. I. — Experiments with Naphtha A. Glass 3. Temperature of the Air 170,8-18°-9. ,T. T'., t'. o t. o M. grms. m. grms. /• grm. y • X. grm. sp. H. 51-5 20-5 20-22 17*23 26-995 15-555 1-745 0-431 0-453 0-0899 51-1 20-3 19-95 16-96 26-985 „ 55 55 55 0-0909 51-7 20-6 20-25 17-24 26-99 55 55 55 55 0-0905 50-9 20-5 20-23 17-25 26-945 55 1-72* 55 Mean ” 0-0930 0-0911 II. — Experiments with Water. Glass 1. Temperature of the Air 16o,0-16°-5. T. T'. t'. t. M. m. /• y • X . sp. H. o o o o grms. grms. grm. grm. 43-0 17-7 17-43 13-82 26-98 14-25 1-855 1-000 0-651 0-0943 43-1 18T