the Greenland coast, and a foot and a half along its opposite margin, and in consequence of this slope proceeds several degrees into the Strait. But as Baffin's Bay and Davis Strait, as has been said before, are traversed by a polar current descending towards the south-east, it ought to have an inclination in that direction; and it is on this account that the current from the east coast of Greenland, after advancing for some time into Davis Strait, is forced to run westwards towards the coast of Labrador, along which it then flows southwards after joining the current from Baffin's Bay. The two united polar currents, whose delivery may be estimated at 1,200,000,000 cubic feet per second, have a breadth of fifty miles, a speed of of a foot per second, and a depth of about 250 fathoms. They flow to the south-east, under the influence of the earth's rotation, which raises them towards the coasts of Labrador and Newfoundland, and continue their course along the latter towards the Gulf Stream until they have doubled Cape Race, when they bend westward and make for Florida. with the experiments, which are grouped under these three sections. (1) Experimental determination of the conditions which govern the development of microzymes in certain organic liquids to be used as tests. Having found in a number of cases that either contact with surfaces which had not been snperheated, or the admixture of water which had not been boiled, was the exclusive cause of the growth of microzymes in the experimental liquid, it was inferred that water is the primary source from whence the germinal particles of bacteria are derived whenever they seem to originate spontaneously in organic solutions. A number of experiments were made with different varieties of water in ordinary use, in order to confirm the observations already made, and to ascer tain if all waters possess the properties in question in a like degree. These experiments are detailed under the second section (2) Distribution of the Germal Matter of Microzymes in ordinary Water. The results under this head were not deemed satisactory. (3) Circumstances which determine the existence of microzymes in organic liquids and tissues, that is, whether the tissues and liquids of the living body participate in the zymotic property which exists in water and moist substances. The conclusion drawn from the facts is, that "it has appeared certain that there is no developmental connection between microzymes and torula cells, and that their apparent association is one of mere juxtaposition. Thus fungi are not developed, notwithstanding the presence of microzymes in the same liquid in which, microzymes being absent, but air having access, they appear with the greatest readiness." Finally, the writer is certain that, although air is the main source of what he calls fungus impreg If now we return to the warm current which, from the Gulf Stream, curves round the south of Iceland, and then spreads itself gradually over the cold waters of the Atlantic, we see that on its arrival at the south point of Greenland, it rises from left to right, from the Gulf Stream to Cape Farewell, about 24 feet, which shows clearly that its course is really to the south. Moreover, this elevation from left to right enables us to give a more satisfactory account of the conditions of currents. In short, the western margin of the warm current accompanying the polar current, ought, along the latter, to have a depth of 1,000 feet and a speed of of a foot; and as the speed of the current di-nation, as distinguished from impregnation with microzymes, yet minishes regularly in approaching the Gulf Stream, and as all the parts of the current follow, as far as Cape Farewell, a direction nearly parallel, it follows that the speed along the Gulf Stream ought to be at the rate of about a foot per second. But if the returning branch of the Gulf Stream proceeds to the south-west with a fall of a foot on its west border, it follows that the depth of the current ought to be 76 feet. By determining in the same way the depth for a certain number of points of a transverse section, and by calculating according to these data the total delivery of the current, we find that it is raised to 410,000,000 cubic feet per second, which perfectly accords with the result which we ought to obtain. If next we inquire how the various parts of the warm surface current move under the united action of the slope and the earth's rotation, we ascertain that this current ought to follow the course of the polar current which gradually absorbs the waters that penetrate underneath, the water of the current being more dense than that of the polar current, and we find at the same time that in thus flowing towards the polar current the water ought to spread itself all over the Atlantic as far as Newfoundland. After having thus shown that the preceding theory accounts in a tolerably complete manner for all the movements of the ocean currents, I shall add, in conclusion, that it is very possible, considering our imperfect knowledge of the progress of currents, that many details may be very different from those which have been expounded above; but, so far as the main question is concerned, I believe I am entitled to say with confidence that the laws of ocean currents are pretty much those which I have attempted to establish. That these laws are equally applicable to the atmospheric currents is evident, and it is scarcely necessary to repeat, that in periods when the differences of temperature on the surface of the globe were greater than at present, all these currents were much stronger, and of a nature otherwise very energetic. SCIENTIFIC SERIALS the two acts may take place at the same moment, germs of torula being often contained in the same liquid media as the germ particles of microzymes. On the Colouring Matter of some Aphides," by H. C. Sorby, F.R.S.-"Observations and Experiments on the Red Blood Corpuscles, chiefly with regard to the Action of Gases and Vapours," by E. Ray Lankester.-" On Undulina, the type of a new group of Infusoria," by E. Ray Lankester." On the Circulation in the wings of Blatta Orientalis and other Insects, and on a new method of injecting the vessels of insects," by H. N. Moseley. After describing the method adopted for preparing and fixing the wings of insects for examination of the circulation, the writer proceeds to his experiences with the cockroach. The corpuscles in Blatta are so large that the circulation may readily be seen with a high power of a simple dissecting microscope. If an insect be carefully tied, the circulation may be observed in action for as long as twelve hours. Abundance of parasites were found in the blood vessels of Blatta and coleopterous insects. The method recommended for the injection of the circulatory system of insects is through the largest artery on the front border of the wing, and the injecting fluid is indigo carmine. -"On the production of Spores in the Radiolaria," by Prof. L. Cienkowski; translated from vol. vii., part 4, of the "Archiv. für Mikroskop. Anatomie." The observations on which this paper is based were mainly made upon Collosphæra and Collozoum. The capsule is the source of the zoospores. In the mature capsule the contents break up into a quantity of little spheroids.—“On_the_Peripheral_Distribution of non-medullated Nerve-fibres," by E. Klein. The writer purposes treating of the nerves of the cornea, those of the nictitating membrane of the frog, of the canal in the tail of the rabbit, and of the mesentery. The present communication is confined to the nerves of the cornea, the remaining subjects are to be embodied in a second paper. SOCIETIES AND ACADEMIES THE Quarterly Journal of Microscopical Science for October, Geclogical Society, Nov. 22.-The Rev. Thomas Wiltshire, 1871. The origin and distribution of Microzymes (Bacteria) M. A., in the chair. Mr. Samuel Baillie Coxon was elected a in water, and the circumstances which determine their existence Fellow of the Society. The following communications were in the tissues and liquids of the living body," by Dr. Burdon read-1. "Notes on some Fossils from the Devonian Rocks Sanderson, F.R.S. This paper is occupied chiefly by details of of the Witzenberg Flats, Cape Colony." By Prof. T. Rupert experiments to determine the conditions which are fatal or Jones, F.G.S. In this paper the author noticed some Devonian favourable to the existence of microzymes in the liquid or gaseous fossils like those of the Bokkeveld, found on Mr. Louw's farm fluids by which we are surrounded, in order to approach one on the Witzenberg Flats, Tulbagh. Orthoceras vittatum, Sanddegree nearer to an understanding of their influence on the pro-berger, was added to the South African list of fossils. The cesses which go on in the living hody. After a definition of "microzymes" the author proceeds to their chemical composition and their relation to the media in which they grow. This portion is brief and incomplete. The remainder of the paper is occupied fossils under notice were stated by the author to help to substantiate the late Dr. Rubidge's view, that the old schists termed "Silurian" by Bain are of Devonian age, and continuous across the colony. Their presence in the Witzenberg Flats was also structure. Mr. Boyd Dawkins, who had recently visited Oxford, stated that he had there examined the remains referred to. There was, however, no tooth found with them of a character to show the nature of the food on which the animal subsisted. But one of his students had lately found in the same pit that had afforded the remains, a tooth corresponding in its principal characters with those of Iguanodon, with which, therefore, the Cetiosaurus seemed to be allied, so that it was probably a vegetable feeder. Mr. J. Parker had lately procured from the Kimmeridge clay a number of Saurian remains, and among them were some vertebræ of Megalosaurus, to which were articulated others presenting distinctly the characters of Streptospondylus. He thought that probably many of the supposed Streptospondylian vertebræ might prove to belong to the cervical region of Dinosaurians. Mr. Seeley disputed the attribution to Cetiosaurus of the vertebræ described, and questioned whether the remains at Oxford might not be assigned to Streptospondylus or Ornithop sis. The depressions in the vertebra, which might be connected with the extension of the air-cells of the lungs, did not exist in Cetiosaurus, but were to be found in Megalosaurus. As to the premaxillary tooth mentioned by Mr. Dawkins, he was uncertain whether it should be referred to what he considered as Cetiosaurus proper, or to the Oxford reptile. Mr. Hulke replied, pointing out that, since the determination of the Oxford reptile as Cetiosaurus, numerous other remains of the same species had been discovered, which had added materially to the basis of classification. The following specimens were exhibited to the meeting :-Devonian fossils from the Witzenberg; exhibited by Professor T. R. Jones, F.G.S., in illustration of his paper. Specimens of Silver Ores from South America; exhibited by Professor Tennant, F.G. S. Fragment of the Wolf Rock, near the Land's End, and section under polarised light; exhibited by Mr. Frank Clarkson, F.G.S. shown to be conclusive against the idea of coal-measures being the trunk vertebræ are described as being of a totally different found there. Mr. Godwin-Austen remarked that the presumed Devonian species of South Africa appeared not to have been completely identified with those of European origin. Although, judging from the range of European marine mollusca, some of which were found of precisely the same species both in Europe and at the Cape, there was nothing surprising in the extension of any old deposit, yet it seemed unreasonable to suppose that the whole district over which the wide-spread Devonian rocks extend could have been submerged at the same time. He traced the original foundation of the Devonian system to the late Mr. Lonsdale, who, in the fossils found in the deposits of Devonshire, thought he traced sufficient grounds for a marked discrimination between those beds and those of Carboniferous age. Mr. Austen had, however, always regarded the Devonian system as merely an older member of the Carboniferous, holding much the same relation to it as the Neocomian to the Cretaceous; and he would be glad to see it recognised, not as an independent system, but merely as the introduction of that far more important system, the Carboniferous, during the deposit of which the globe was subject to the same physiographical conditions. Mr. Etheridge did not agree with Mr. Austen as to the suppression of the name of Devonian system, and commented on its wide-spread distribution, and on the peculiar facies of its fossils, and their importance as a group. He was rather doubtful as to specific determinations arrived at from casts. Though the species of many fossils of Queensland procured by Mr. Daintree did not correspond with those of European areas, yet some of the corals were identical with those of South and North Devon, as were also the lithological characters of the containing beds. Mr. Seeley objected to any attempt to supersede the arrangements of the South African rocks in accordance with the local phenomena, by correlating them too closely with any European series. The recognition of the correspondence in forms seemed to him more to prove a similarity of conditions of life than any absolute synchronism. As to the connection between the Devonian and Carboniferous systems, he agreed with Mr. Austen in regarding the one as merely constituting the natural base of the other. 2. "On the Geology of Fernando Noronha (S. lat. 3° 50′, W. long. 32° 50')." By Alexander Rattray, M.D. (Edin.), Surgeon R.N. Communicated by Prof. Huxley, F. R.S. The author described the general geological structure of Fernando Noronha and the smaller islands which form a group with it. The surface-rock was described as a coarse conglomerate, composed of rounded basaltic boulders and pebbles, in a hard, dark red, clayey matrix. This overlies a hard, dark, fine-grained basalt, which forms the most striking of the bluffs, cliffs, and outlying rocks. The highest peaks in the group consist of a fine-grained, light grey granite. The author remarked upon the possible relation of the geology of these islands to that of the neighbouring continent of South America, and stated that there is evidence of the islands having | been elevated to some extent at a comparatively recent period. 3. "Note on some Ichthyosaurian Remains from Kimmeridge Bay, Dorset." By Mr. J. W. Hulke, F.R.S. The author noticed some teeth found, with a portion of an Ichthyosaurian skull, in the Kimmeridge clay of Dorsetshire. The fragments of the snout were said to indicate that it was about three feet long and proportionally stout. The author indicated the character by which these teeth were distinguishable from those of various known species of Ichthyosaurus, and stated that they approached most closely to those of the Cretaceous I. campylodon. Mr. Seeley did not consider that, in the main, the teeth of Reptilia afforded any criteria for specific determination. In the Cambridge Greensand, though there were five species of Ichthyosaurus, possibly including a second genus, the teeth found were so closely similar that it would have been impossible, from them only, to identify more than one species. Mr. Boyd Dawkins recognised in the specimens exhibited by Mr. Hulke a form of tooth he had found in the Kimmeridge beds of Shotover, near Oxford, but which he had been hitherto unable to attribute to any recognised species. He could not fullv agree with Mr. Seeley as to the ab. sence of specific criteria in the teeth of Saurians, as, from his own experience, he was inclined to attribute some importance to their external sculpturing. 4. "Appendix to a 'Note on a New and Undescribed Wealden Vertebra,' read 9th February, 1870, and published in the Quarterly Journal for August in that year." By Mr. J. W. Hulke, F. R.S. The author generically identified this vertebra with Ornithopsis, Seeley, Streptospondylus, Owen, and Cetiosaurus, Owen, taking the last to be typified by the large species in the Oxford Museum. He remarked that if this be the type of Cetiosaurus, C. brevis, Owen, can hardly belong to it, as Royal Geographical Society, November 27.-Major-Gen. Sir H. C. Rawlinson, K. C. B., president, in the chair.-The President read a letter from Dr. Kirk, of Zanzibar, to the late Sir Roderick Murchison, giving news of a serious outbreak in Unyanyembe, the country lying on the main route to Lake Tanganyika, which is likely to prevent communication with Dr. Livingstone for some time to come. The letter was dated September 25th, and stated that a native chief, having been attacked by a force of Arabs settled in Unyanyembe, had waited his assailants in ambush when returning with their plunder, and had killed many of the principal men. Mr. Stanley, an American gentleman, who was travelling to Lake Tanganyika, and who had charge of letters and stores for Dr. Livingstone, was in the fray, and had been deserted by the Arabs. He had also been ill of fever, and his future plans were uncertain. A report, to which Dr. Kirk attached little credence, had spread in Zanzibar, to the effect that Livingstone and the Arab Mohammed bin Gharib, with whom he had been living, were returning round the south end of Tanganyika, and out of the region of disturbances. Captain R. F. Burton, in commenting upon this letter, informed the meeting that similar affrays between Arab trading parties and the natives had occurred before, and that this unsettled state might continue for two or three years. He thought that Living. stone would find no difficulty in returning by the south of the lake, and that a fearless man like him, speaking the native languages, would be able to pass through the disturbed districts. He had not the slightest misgiving with regard to him. - Captain Burton then read a paper On the Volcanic Region east of Damascus and the Cave of Umm Nírán." This was a narrative of a hazardous journey of fifteen days, which he had performed in May and June 1871, in company with Mr. C. F. Tyrwhitt Drake, through the Safá Region, the Oriental Trachon of the Greek geographers, a wide extent of ancient lava-fields, the hills of which, like little pyramids, dot the eastern horizon, as viewed from Damascus. The danger and difficulty of visiting the many interesting places in this district arose simply from certain petty tribes of Bedouin, descendants of the refractory robbers of the Trachonitís, who dwell in the highlands of the Hauran, under the patronage of the Druses. The worst are the Ghiyas and the Shtayá, who although they have given hostages, were allowed, during the author's stay at Damascus, to ride the country within three hours of the walls, and to plunder the villages. During one of his excursions a skirmishing party of Ghiyas attacked his party, severely wounding one of his companions. During his journey 120 inscriptions were collected, including three in the Palmyrene dialect. The volcanic outbreak to which the district owes its singular character the author was inclined to attribute to the epoch when the Eastern Desert, a flat stoneless tract, extending from the Trachonitis to the Euphrates, was a mighty inlet of the Indian Ocean, having its northern limit in the range of limestones and sandstones, the furthest outliers of the AntiLibanus, upon whose southern and eastern feet Palmyra is built, and which runs eastward to the actual valley of the great river. Mr. Drake took a continuous set of compass bearings during the journey, which had enabled him to draw an excellent map of the region. Mr. W. Giffard Palgrave spoke on the subject of the paper, stating that Captain Burton was the only European who had properly explored El Safá. He had himself explored about two-thirds of the distance, without, however, reaching the cavern of Umm Nírán. His own visit terminated at the southern part of the El Leja, the great volcanic district celebrated for the destruction of the Egyptian army in the time of Ibrahim Pacha, when they attacked the Druses in the basaltic labyrinth.A second paper was read, "On the Geography of Southern Arabia," by the Baron Von Maltzan, which contained interesting elucidations of the physical configuration and tribal distribution of the region north of Aden, compiled by systematic interrogation of Arabs at Aden. EDINBURGH Naturalists' Field Club.-The annual business meeting of this club was held on Wednesday, the 29th ult., when Mr. Skerving was elected President and Mr. John Brown Honorary Secretary and Treasurer. A vote of thanks was accorded to Mr. Taylor, the retiring secretary. The club now numbers 87 members; and 13 excursions have been made to places of local interest during the summer months. PARIS Academy of Sciences, November 27.-M. Chasles presented a theorem concerning the harmonic axes of the geometrical curves, in which there are two series of points corresponding anharmonically on a unicursal curve.-M. P. A. Favre communicated the continuation of his thermic investigations upon electrolysis, in which he gave the results of experiments made especially with the voltameter with plates of copper immersed in sulphate of copper.-M. de Fonvielle presented a note on musical sounds produced at the opening of the valve in balloon ascents.-M. des Cloiseaux communicated some optical and crystallographical observations upon montebrasite and the amblygonite of Montebras, the former a new fluophosphate of alumina, soda, and lithia.-A letter was read from M. Moison describing the use of sea-water for making bread in the environs of Cancale. -M. H. Sainte-Claire Deville presented a note by M. T. Schloesing on the separation of potash and soda. The author's process is founded upon that proposed by Serullas, in which perchloric acid is employed. He uses, instead of this acid, pure perchlorate of ammonia, treated with weak nitro-muriatic acid. The preparation of the perchlorate is described by the author.— M. Chabrier presented some further observations on the alternate predominance of nitrous and nitric acids in rain-water. The author finds that in calm weather nitrous acid is present in excess in rain water, whilst nitric acid predominates in stormy weather. -M. Chevreul communicated a letter from M. Sacc on the properties of drying oils, with regard to which M. Thenard also made some observations.-A note by MM. Dusant and C. Bardy on the phenoles was presented by M. Cahours.-M. C. Bernard communicated a note by M. E. Faivre on the movements of the sap through the bark. The author describes a series of experiments made upon mulberry trees, and demonstrates that it is in the bark, and particularly in its liber, that the ascending and descending movements of the sap take place.-M. Joseph-Lafosse presented some observations on the germination of seeds submerged in 1870-71 during the inundation of the neighbourhood of Carenton for the defence of Cherbourg. He stated that after the retirement of the water many plants sprang up in unusual abundance and vigour, and suggested that experiments should be made upon the effects of long soaking upon the germination of the seeds of useful plants.-A letter from M. A. de la Rive on M. Marey's recent communications relating to the electrical discharge of the torpedo was read. The author considered the action of the nerves in causing muscular contraction to be electrical, and that the electrical effect produced by the apparatus of the torpedo was caused by the accumulation in it of the energy of the immense multitude of nervous filaments with which it is supplied.-M. C. Bernard presented a note by M. L. Reverdin on epidermic grafting, describing and discussing the phenomena produced by the transfer of portions of skin from one living animal to another. The author maintains that the adherence of these grafts is produced principally by the epidermis, the dermis having only a secondary action.—M. S. Meunier, in a note on meteoric metamorphism, described the transformation of aumalite into chantonnite by exposure for a quarter of an hour to a red heat, which confirms his conclusion that the latter is the eruptive form of the former. BOOKS RECEIVED ENGLISH.-The Young Collector's Handybook of Botany: Rev. H. N Dunster (Reeve and Co.).-Journal of the Iron and Steel Institute. Vol. II., No. 4.-Astronomical Phenomena in 1872: W. F. Denning (Wyman and Son). AMERICAN AND COLONIAL.-The Fossil Plants of the Devonian and Upper Silurian Formations of Canada, 21 plates: Principal Dawson.-Elements of Chemistry, Vol. II. G. Hinrichs. FOREIGN-Zeitschrift für Ethnologie; Supplement Band: Bastian and Hartmann. (Through Williams and Norgate.) -Die Sonne, von P. A Secchi, autorisirte Ausgabe von Dr H. Schellen, ite Abtheilung -Sitzungs berichte der Gesellschaft naturforschender Freunde zu Berlin, 1870.-Die ältesten Spuren Menschen in Europa: A. Müller. DIARY THURSDAY, DECEMBER 7. Part VI. ROYAL SOCIETY, at 8.30.-On the Fossil Mammals of Australia. FRIDAY, DECEMBER 8. SUNDAY, DECEMBER 10. SUNDAY LECTURE SOCIETY, at 4.-On the Optical Construction of the Eye : Dr. R. E. Dudgeon. MONDAY, DECEMBER II. ROYAL GEOGRAPHICAL SOCIETY, at 8.30. TUESDAY, DECEMBER 12. PHOTOGRAPHIC SOCIETY, at 8. WEDNESDAY, DECEMBER 13. SOCIETY OF ATS, at 8.-Observations on the Esparto Plant: Robert Johnston ARCHEOLOGICAL INSTITUTE, at 8. THURSDAY, DECEMBER 14. ROYAL SOCIETY, at 8.30. CONTENTS THE CHAIRS OF SCIENCE IN THE SCOTTISH UNIVERSITIES The Origin of Insects.-B. T. LowNE, M.B. Cause of Low Barometric Pressure.-A. WCJEIKOFER The Solar Halo-GEO. C. THOMPSON. ON THE ZIPHIOID WHALES. By Prof. W. H. FLOWER, F.R.S. ARCTIC EXPLORATIONS. By Dr. JOHN RAE, F.R G.S. COLDING ON THE LAWS OF CURRENTS IN ORDINARY CONDUITS AND IN THE SEA. III. SCIENTIFIC SERIALS SOCIETIES AND ACADEMIES DR. THURSDAY, DECEMBER 14, 1871 THE COPLEY MEDALIST OF 1871 R. JULIUS ROBERT MAYER was educated for the medical profession. In the summer of 1840, as he himself informs us, he was at Java, and there observed that the venous blood of some of his patients had a singularly bright red colour. The observation riveted his attention; he reasoned upon it, and came to the conclusion that the brightness of the colour was due to the fact that a less amount of oxidation sufficed to keep up the temperature of the body in a hot climate than in a cold one. The darkness of the venous blood he regarded as the visible sign of the energy of the oxidation. It would be trivial to remark that accidents such as this, appealing to minds prepared for them, have often led to great discoveries. Mayer's attention was thereby drawn to the whole question of animal heat. Lavoisier had ascribed this heat to the oxidation of the food. One great principle, says Mayer, of the physiological theory of combustion, is that under all circumstances the same amount of fuel yields by its perfect combustion the same amount of heat; that this law holds good for vital processes; and that hence the living body, notwithstanding all its enigmas and wonders, is incompetent to generate heat out of nothing. But beyond the power of generating internal heat, the animal organism can also generate heat outside of itself. A blacksmith, for example, by hammering can heat a nail, and a savage by friction can warm wood to its point of ignition. Now unless we give up the physiological axiom that the living body cannot create heat out of nothing, we are driven," says Mayer, "to the conclusion that it is the total heat generated within and without that is to be regarded as the true calorific effect of the matter oxidised in the body." From this again he inferred that the heat generated externally must stand in a fixed relation to the work expended in its production. For, supposing the organic processes to remain the same; if it were possible, by the mere alteration of the apparatus, to generate different amounts of heat by the same amount of work, it would follow that the oxidation of the same amount of material would sometimes yield a less, sometimes a greater, quantity of heat. Hence," says Mayer, "that a fixed relation subsists between heat and work, is a postulate of the physiological theory of combustion." 66 This is the simple and natural account given subsequently by Mayer himself of the course of thought started by his observation in Java. But the conviction once formed that an unalterable relation subsists between work and heat, it was inevitable that Mayer should seek to express it numerically. It was also inevitable that a mind like his, having raised itself to clearness on this important point, should push forward to consider the relationship of natural forces generally. At the beginning of 1842 his work had made considerable progress; but he had become physician to the town of Heilbronn, and the duties of his profession limited the time which he could devote to purely scientific inquiry. He thought it wise, therefore, VOL. V. to secure himself against accident, and in the spring of 1842 wrote to Liebig, asking him to publish in his "Annalen a brief preliminary notice of the work then accomplished. Liebig did so, and Dr. Mayer's first paper is contained in the May number of the "Annalen" for 1842. Mayer had reached his conclusions by reflecting on the complex processes of the living body; but his first step in public was to state definitely the physical principles on which his physiological deductions were to rest. He begins, therefore, with the forces of inorganic nature. He finds in the universe two systems of causes which are not mutually convertible ;-the different kinds of matter, and the different forms of force. The first quality of both he affirms to be indestructibility. A force cannot become nothing, nor can it arise from nothing. Forces are convertible, but not destructible. In the terminology of his time, he then gives clear expression to the ideas of potential and dynamic energy, illustrating his point by a weight resting upon the earth, suspended at a height above the earth, and actually falling to the earth. He next fixes his attencases where motion is apparently destroyed without producing other motion; on the shock of inelastic bodies, for example. Under what form does the vanished motion maintain itself? Experiment alone, says Mayer, can help us here. He warms water by stirring it; he refers to the force expended in overcoming friction. Motion in both cases disappears, but heat is generated, and the quantity generated is the equivalent of the motion destroyed. Our locomotives, he observes with extraordinary sagacity, may be compared to distilling apparatus. The heat beneath the boiler passes into the motion of the train, and it is again deposited as heat in the axles and wheels. A numerical solution of the relation between heat and work was what Mayer aimed at, and towards the end of his first paper he makes the attempt. It was known that a definite amount of air, in rising one degree in temperature, can take up two different amounts of heat. If its volume be kept constant, it takes up one amount; if its pressure be kept constant, it takes up a different amount. These two amounts are called the specific heat under constant volume and under constant pressure. The ratio of the first to the second is as 1 : 1421. No man, to my knowledge, prior to Dr. Mayer, penetrated the significance of these two numbers. He first saw that the excess o ̊421 was not, as then universally supposed, heat actually lodged in the gas, but heat which had been actually consumed by the gas in expanding against pressure. The amount of work here performed was accurately known, the amount of heat consumed was also accurately known, and from these data Mayer determined the mechanical equivalent of heat. Even in this first paper he is able to direct attention to the enormous discrepancy between the theoretic power of the fuel consumed in steam-engines and their useful effect. Though this first paper contains but the germ of his further labours, I think it may be safely assumed that, as regards the mechanical theory of heat, this obscure Heilbronn physician in the year 1842 was in advance of all the scientific men of the time. Having, by the publication of this paper, secured him H self against what he calls "Eventualitäten," he devoted every hour of his spare time to his studies, and in 1845 published a memoir which far transcends his first one in weight and fulness, and, indeed, marks an epoch in the history of science. The title of Mayer's first paper was, Remarks on the Forces of Inorganic Nature." The title of his second great essay was, "Organic Motion in its Connection with Nutrition." In it he expands and illustrates the physical principles laid down in his first brief paper. He goes fully through the calculation of the mechanical equivalent of heat. He calculates the performances of steam-engines, and finds that 100 lbs. of coal in a good working engine produce only the same amount of heat as 95 lbs. in an unworking one; the 5 lbs. disappearing having been converted into work. He determines the useful effect of gunpowder, and finds 9 per cent. of the force of the consumed charcoal invested on the moving ball. He records observations on the heat generated in water when agitated by a pulping engine of a paper manufactory, and calculates the equivalent of that heat in horsepower. He compares chemical combination with mechanical combination-the union of atoms with the union of falling bodies with the earth. He calculates the velocity with which a body starting at an infinite distance would strike the earth's surface, and finds that the heat generated by its collision would raise an equal weight of water 17,356° C. in temperature. He then determines the thermal effect which would be produced by the earth itself falling into the sun. So that here, in 1845, we have the germ of that meteoric theory of the sun's heat which Mayer developed with such extraordinary ability three years afterwards. He also points to the almost exclusive efficacy of the sun's heat in producing mechanical motions upon the earth, winding up with the profound remark, that the heat developed by friction on the wheels of our wind and watermills comes from the sun in the form of vibratory motion; while the heat produced by mills driven by tidal action is generated at the expense of the earth's axial rotation. Having thus with firm step passed through the powers of inorganic nature, his next object is to bring his principles to bear upon the phenomena of vegetable and animal life. Wood and coal can burn; whence come their heat, and the work producible by that heat? From the immea. surable reservoir of the sun. Nature has proposed to herself the task of storing up the light which streams earthward from the sun, and of casting into a permanent form the most fugitive of all powers. To this end she has overspread the earth with organisms which, while living, take in the solar light, and by its consumption generate forces of another kind. These organisms are plants. The vegetable world indeed constitutes the instrument whereby the wave-motion of the sun is changed into the rigid form of chemical tension, and thus prepared for future use. With this prevision, as shall subsequently be shown, the existence of the human race itself is inseparably connected. It is to be observed that Mayer's utterances are far from being anticipated by vague statements regarding the "stimulus" of light, or regarding coal as "bottled sunlight." He first saw the full meaning of De Saussure's observation of the reducing power of the solar rays, and gave that observation its proper place in the doctrine of conservation. In the leaves of a tree, the carbon and oxygen of carbonic acid, and the hydrogen and oxygen of water, are forced asunder at the expense of the sun, and the amount of power thus sacrificed is accurately restored by the combustion of the tree. The heat and work potential in our coal strata are so much strength withdrawn from the sun of formerages. Mayer lays the axe to the root of many notions regarding the vital force which were prevalent when he wrote. With the plain fact before us that plants cannot perform the work of reduction, or generate chemical tensions, in the absence of the solar rays, it is, he contends, incredible that these tensions should be caused by the mystic play of the vital force. Such an hypothesis would cut off all investigation; it would land us in a chaos of unbridled phantasy. "I count," he says, "therefore, upon assent when I state as an axiomatic truth that during vital processes the conversion only and never the creation of matter or force occurs." Having cleared his way through the vegetable world, as he had previously done through inorganic nature, Mayer passes on to the other organic kingdom. The physical forces collected by plants become the property of animals. Animals consume vegetables, and cause them to reunite with the atmospheric oxygen. Animal heat is thus produced, and not only animal heat but animal motion. There is no indistinctness about Mayer here; he grasps his subject in all its details, and reduces to figures the concomitants of muscular action. A bowler who imparts to an 8-lb. ball a velocity of 30 feet consumes in the act of a grain of carbon. A man weighing 150 lbs., who lifts his own body to a height of 8 feet, consumes in the act 1 grain of carbon. In climbing a mountain 10,000 feet high, the consumption of the same man would be 2 oz. 4 drs. 50 grs. of carbon. Boussingault had determined experimentally the addition to be made to the food of horses when actively working, and Liebig had determined the addition to be made in the case of men. Employing the mechanical equivalent of heat, which he had previously calculated, Mayer proves the additional food to be amply sufficient to cover the increased oxidation. But he does not content himself with showing in a general way that the human body burns according to definite laws, when it peforms mechanical work. He seeks to determine the particular portion of the body consumed, and in doing so executes some noteworthy calculations. The muscles of a labourer 150 lbs. in weight, weigh 64lbs.; when perfectly desiccated they fall to 15 lbs. Were the oxidation corresponding to that labourer's work. exerted on the muscles alone, they would be utterly consumed in 80 days. The heart furnishes a still more striking example. Were the oxidation necessary to sustain the heart's action exerted upon its own tissue, it would be utterly consumed in 8 days. And if we confine our attention to the two ventricles, their action would be sufficient to consume the associated muscular tissue in 3 days. Here, in his own words, emphasised in his own way, is Mayer's pregnant conclusion from these calculations :— "The muscle is only the apparatus by means of which the conversion of the force is effected; but it is not the substance consumed in the production of the mechanical effect." He calls the blood "the oil of the lamp of life;" it is the slow-burning fluid whose chemical force in the furnace of the capillaries is sacrificed to produce animal motion. This was Mayer's conclusion twenty-six years ago. It was in complete opposition to the scientific conclusions of his time; but eminent investigators have since amply verified it. |