THE BEGINNINGS OF LIFE. 



the mechanical force employed for the friction V For, 

 as Sir Humphrey Davy reasoned, a motion or vibration 

 of the corpuscles of bodies must be necessarily gener- 

 ated by friction and percussion, and so, he adds, c we 

 may reasonably conclude that this motion or vibra- 

 tion is heat, or the repulsive power.' Then, in 1827, 

 Lardner Vanuxem published in Philadelphia an essay 2 

 in which he speaks of caloric, light, electricity, and 

 magnetism as being mutually convertible. His utter- 

 ances are, however, somewhat dubious, since he at 

 first treats of them as c four different states' of c one 

 kind of repulsive matter', though, further on, he ac- 

 knowledges that the existence of these as c four dis- 

 tinct fluids, or kinds of aethereal matter, is inadmis- 

 sible; for this conversion or change of characters is 

 analogous to what are called the properties of bodies 

 and not to the bodies themselves.' Again, in 1839, 

 Seguin, in a work entitled ' De ^Influence des Chemins 

 de Fer,' called attention to the mutual convertibility of 

 heat and mechanical force, and he gave a calculation 

 of their equivalent relation not differing materially 

 from that afterwards published by Mayer and Joule. 

 In January, 1842, in a lecture delivered before the 

 Royal Institution, Professor Grove declared that c light, 

 heat, electricity, magnetism, motion, and chemical 

 affinity are all convertible material affections;' and in 



1 Orme's ' Science of Heat,' 1869, p. 163. 



2 'On the Ultimate Principles of Chemistry, Natural Philosophy, 

 and Physiology.' 



