JULIUS ROBERT MAYER. 401 



strike the earth's surface, and finds that the heat generated by its collision would 

 raise an equal weight of water 17,356 0. in temperature. He then determines 

 the thermal effect which would he 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 

 afterward. 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 in 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 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 immeasurable 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, con- 

 stitutes 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 pre- 

 vision, as will 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 re- 

 garding coal as " bottled sunlight." He first saw the full meaning of De Saus- 

 sure's observation as to the reducing power of the solar rays, and gave that ob- 

 servation 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 former ages. Mayer lays the axe to the root of the notions regarding 

 " vital force " which were prevalent when he wrote. With the plain fact before 

 us that in the absence of the solar rays plants can not perform the work of reduc- 

 tion, or generate chemical tensions, "it is," he contends, "incredible that these 

 tensions should be caused by the mystic play of the vital force." Such an hy- 

 pothesis would cut off all investigation ; it would land us in a chaos of unbridled 

 phantasy. " I count," he says, " therefore, upon your agreement with me 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. Ani- 

 mals consume vegetables, and cause them to reunite with the atmospheric oxy- 

 gen. 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 eight-pound ball a velocity of thirty feet, consumes 

 in the act one-tenth of a grain of carbon. A man weighing 150 pounds, who 

 lifts his own body to a height of eight feet, consumes in the act one grain of 



vor,. xv. 26 



