April ^, 1878] 



NATURE 



451 



25, 1 8 14. In the neighbouring University of Tubingen? 

 he underwent the usual course of studies in the medical 

 faculty ; and after obtaining his degree as physician, 

 passed some time in the hospitals of Miinich and Paris. 

 His entrance into professional life was as ship's surgeon 

 on an East India vessel. While thus engaged he made 

 an observation apparently unconnected with, but really 

 the origin of, all his subsequent investigaticms. To quote 

 from Prof. Tyndall's paper referred to : — 



" In the summer of 1840, 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. . . ." 



It was the idea thus suggested which he worked out to its 

 issue in his great generalisation. In 1841 he returned from 

 Batavia, and settled in his native town. Here he devoted 

 the spare hours from his professional duties to the con- 

 sideration of various unsolved physical problems. Although 

 almost entirely isolated from scientific companionship, 

 •with next to no opportunity for experimental research, and 

 limited in time, he evolved in a short period a succession 

 of theoretical views, which in point of originality, boldness, 

 and comprehensive grasp of facts, stand among the fore- 

 most in the history of physics. Mayer's first contribution to 

 scientific literature — '' tjeber die Krafte der unbelebten 

 Natur" — appeared in Liebig's Annaleti in 1842, and con- 

 tained within the space of eleven pages the forecast of 

 the mechanical theory of heat, as accepted at present. 

 At this time the caloric theory still found numerous advo- 

 cates, despite the classic experiments of Rumford, of 

 Davy, and of others ; and but a small minority ventured 

 to defend, from one standpoint or another, the idea of an 

 intimate connection between heat and motion. It was 

 reserved for Mayer to sum together the scattered 

 facts, and to mould from them definite views on the 

 nature of heat. With his introduction of the expression 

 " the mechanical equivalent of heat," and the clear expo- 

 sition of the mutual interchangeability of heat and 

 mechanical energy, he dealt the last blow to the old 

 theory, and thus largely helped to place on a firm founda- 

 tion the new doctrines of the conservation and transfor- 

 mation of energy. But in this Mayer did not stand 

 alone, nor was he the only one who had a firm hold of 

 the conceptions which have been so fruitful of result. 

 The quiet sap of experiment was going on side by side 

 •with these daring reconnaissances beyond the borders of 

 the known and proved, and our own Joule, whose work 

 does not suffer because he was not the sole worker and 

 thinker in the field, was conducting those researches 

 •which have earned for him also an undying name and 

 fame. 



Three years elapsed before the appearance of Mayer's 

 next work in 1845, on " Organic Movement in Connection 

 with the Transformation of Matter." In this brochure of 

 100 pages, he details at greater length the new theory, 

 and with a most extensive, varied, and novel series of 

 illustrations from every branch of natural science and 

 natural history, establishes the principles that all the so- 

 called forces are interchangeable forms of energy — the 

 one sole force — that energy is never created or destroyed, 

 and that all natural phenomena are accompanied by a 

 change of the form of energy. The logical consequences 

 of the mechanical theory of heat were followed to their 

 uttermost limits in Mayer's work " On Celestial Dyna- 

 mics," in 1848. Here he seeks to solve the difficult prob- 



lems of determining the thermal effects of the movements 

 in the universe, the maintenance of the supply of solar 

 heat, &c. One chief source of the latter he considers to 

 be the heat evolved by the fall of innumerable meteorites 

 &c., into the sun. 



His " Remarks on the Mechanical Equivalent of 

 Heat," in 1851, was his last notable contribution to 

 the development of this subject. It possesses the 

 same fulness of original ideas as its predecessors, and 

 in point of vividness and clearness of conception and 

 definition, can only be rivalled by Tyndall's " Heat as a 

 Form of Motion." A collected edition of his writings, 

 under the title of " Die Mechanik der Wiirme," appeared 

 at Stuttgart, 1867, and a second edition in 1874 ; this was 

 followed by " Naturwissenschaftliche Vortrage" (Stutt- 

 gart, 1871), and two papers under the title of " Die Torri- 

 celli'sche Leere" and " Ober Auslosung" (Stuttgart, 1876), 

 The controversy on the priority of his discoveries led to 

 disturbances in the mental health of the great savant, 

 which, however, was in time completely restored. Dr. 

 Mayer was of an original and witty turn of mind, unre- 

 strained in a small company, but otherwise modestly 

 retiring within himself. 



In measuring the value of Mayer's scientific achieve- 

 ments it must not be forgotten that he published his theory 

 at an epoch when physicists were directing their attention 

 especially to this very subject, and that in Denmark and 

 England the experiments were well advanced, v/hich led 

 to the complete establishment of our present knowledge 

 of the character of heat and energy. It is, however, diffi- 

 cult to believe that any of his rivals in this province could 

 have developed and amplified the theory in the masterly 

 manner shown by this obscure German physician. In 

 perusing his works, one scarcely knows which to admire 

 most, the wonderful powers of classification and breadth 

 of knowledge exhibited in every page, or the charming 

 simplicity, clearness, and aptness of illustration with 

 which abstruse theoretical questions are put within the 

 comprehension of a tyro in science. Certainly in view of 

 his life and surroundings, the contributions of Mayer to 

 the progress of physics occupy a unique position in the 

 history of science. To quote Dr. Tyndall again — 



" Mayer grasped the mechanical theory of heat •with 

 commanding power, illustrating it and applying it in the 

 most diverse domains. He began, as we have seen, with 

 physical principles ; he determined the numerical relation 

 between heat and work ; he revealed the source of the 

 energies of the vegetable world, and showed the relation- 

 ship of the heat of our fires to solar heat. He followed 

 the energies which were potential in the vegetable up to 

 their local exhaustion in the animal. But in 1845 

 a new thought was forced upon him by his calculations. 

 He then for the first time drew attention to the astound- 

 ing amount of heat generated by gravity where the force 

 has sufficient distance to act through. He proved, as I 

 have before stated, the heat of collision of a body falling 

 from an infinite distance to the earth, to be sufficient to 

 raise the temperature of a quantity of water equal to the 

 falling body in weight 17,356° C. He also found in 1845 

 that the gravitating force between the earth and sun 

 was competent to generate an amount of heat equal 

 to that obtainable from the combustion of 6,000 times the 

 weight of the earth of solid coal. With the quickness of 

 genius he saw that we had here a power sufficient to pro- 

 duce the enormous temperature of the sun, and also to 

 account for the primal molten condition of our own planet. 

 Mayer shows the utter inadequacy of chemical forces, as 

 we know them, to produce or maintain the solar tempera- 

 ture. He shows that were the sun a lump of coal, it would 

 be utterly consumed in 5,000 years. He shows the diffi- 

 culties attending the assumption that the sua is a coolmg 

 body ; for supposing it to possess the high specific heat 

 of water, its temperature would fall 15,000° in 5,000 years. 

 He finally concludes that the light ai,d heat of the sun 



