470 POPULAR SCIENCE MONTHLY. 



energy and, inferentially, of the quantivalent relations of all energies. 

 He originated the now usual method of determining the quantivalence 

 of heat and thermal and dynamical forms of energy by the storage of 

 the heat of friction in a mass of water, and, by the churning of liquids, 

 of similarly storing the heat of fluid-friction. He adopted the view that 

 the energy developed in the animal system is the measure of a certain 

 proportion of the stored energy of the food thus utilized. Thus he ex- 

 tended the principle of persistence to the organic world and to living 

 creatures, opening the way to the final generalizations and conclusions 

 of the enunciator of the so-called 'Law of Substance.' 



Thus Eumford was the first to prove by experimental investigation 

 the transformability of the energies, to exhibit the principle in its most 

 important example and to derive, by physical research, the principle of 

 the thermodynamic equivalence of energies and the fact of heat being 

 simply a form of energy and a mode of motion of substance. 



Mayer seems to have been the first to recognize a now well-under- 

 stood fact: that, if we are to gain a more effective development of the 

 energies, potential in our fuels, which are practically our only sources 

 of commercially useful energy, we must find a way to transform the po- 

 tential energy of chemical union directly into some other form than the 

 thermal and by some other than the thermodynamic process. He says* 

 that 'the evident wastes of the thermodynamic process as illustrated in 

 our best steam engines justify us in seeking other methods of energy- 

 transformation,' more particularly by the transformation into motion of 

 electricity obtained by chemical means. 



Mayer was probably the first to write under the definite title 'The 

 Mechanical Equivalent of Heat.'f He was the first to declare, in so many 

 words: 'the vis viva of the universe is a constant quantity.' t He stated 

 that 'the heat produced mechanically by the organism must bear an in- 

 variable quantitative relation to the work expended in producing it.' 



This he deduced from his 'physiological theory of combustion.' He 

 anticipates the idea of the permanence of the universe in its present 

 general aspect by the suggestion that this redistribution of energy, 'de- 

 graded' by other phenomena, may be effected 'by the falling together of 

 previously invisible double stars' or equivalent phenomena. § He finds 

 by computation that the energy transformed through such collisions 

 'would considerably exceed that which an equal weight of matter could 

 furnish by the most intense process of chemical action' — in other words: 

 it would resolve the solid mass into its elementary atoms; which is pre- 



*Torces of Inorganic Nature; 'Liebig's Journal/ 1842. 

 f 'The Mechanical Equivalent of Heat,' 1851. 

 $ 'Celestial Dynamics,' 1848. 



§'The Mechanical Equivalent of Heat,' 1851. 



