n8 



NA TURE 



{Dec. 14, 1871 



self against what he calls " Eventualitaten," 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 illus- 

 trates 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 per- 

 formances 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. dis- 

 appearing having been converted into work. He deter- 

 mines the useful effect of gunpowder, and finds g 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 engme of a paper manu- 

 factory, and calculates the equivalent of that heat in horse- 

 power. He compares chemical combination with mecha- 

 nical 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, '^ve 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 deve- 

 loped by friction on the wheels of our wind and water- 

 mills 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 prin- 

 ciples to bear upon the phenomena of vegetable and ani- 

 mal 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. 

 Itis to be observedthat 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 sacri- 

 ficed 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 com'crsion 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 j'q of a grain of carbon. A man weighing 

 1 50 lbs., who lifts his own body to a height of 8 feet, con- 

 sumes in the act i grain of carbon. In climbing a mountain 

 io,ooo feet high, the consumption of the same man would be 

 2 oz. 4 drs. 50 grs. of carbon. Boussingault had deter- 

 mined 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 o.xidation. 



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 con- 

 sumed, and in doing so executes some noteworthy calcu- 

 lations. 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 con- 

 sumed in 80 days. The heart furnishes a still more strik- 

 ing 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 atten- 

 tion 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 t/ie 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 fur- 

 nace of the capillaries issacrificed toproduceanimal 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. 



