58 LIFE AND DEATH. 



On the threshold of this new science we find in- 

 scribed the principle of the conservation of energy^ 

 which has been presented to us by some as Nature's 

 supreme law, and which we may say dominates 

 natural philosophy. Its discovery marked a new era 

 and accomplished a profound revolution in our con- 

 ception of the universe. It is due to a doctor, Robert 

 Mayer, who practised in a little town in Wurtemberg, 

 and who formulated the new principle in 1842, and 

 afterwards developed its consequences in a series of 

 publications between 1845 and 1851. They remained 

 almost unknown until Helmholtz, in his celebrated 

 memoir on the conservation of force, brought them to 

 light and gave them the importance they deserved. 

 From that time forward the name of the doctor of 

 Heilbronn, until then obscure, has taken its place 

 among the most honoured names in the history of 

 science.^ 



^ Mayer's claim to fame has been disputed. A Scotch physicist, 

 P. G. Tait, has investigated the history of the law of the con- 

 servation of energy, which is the history of the idea of energy. 

 The conception has taken time to penetrate the human mind, 

 but its experimental proof is of recent date. P. G. Tait finds an 

 almost complete expression of the law of the conservation of 

 energy in Newton's third law of motion — namely, "the law of the 

 equality of action and reaction," or rather, in the second ex- 

 planation which Newton gave of that law. In fact, it was from 

 this law that Helmholtz deduced it in 1847. He showed that 

 the law of the equality of action and reaction, considered as a 

 law of nature, involved the impossibility of perpetual motion, 

 and the impossibility of perpetual motion is, in another form, the 

 conservation of energy. 



At a meeting of the Academy of Science, at Berlin, 28th 

 March 1878, Du Bois-Reymond violently attacked Tail's con- 

 tention. The honour of having been the first to conceive of the 

 idea of energy and conservation was awarded to Leibniz. 

 Newton had no right to it, for he appealed to divine intervention 



