72 THE ADVANCE OF SCIENCE 



heat. The loss of the masses is the gain 

 of their particles. 

 Earlier Before 1843, however, the doctrine of 



proaches ^ ne conservation of energy had been ap- 

 doctrine P roacne( i- Bacon's chief contribution to 

 of con- positive science is the happy guess (for 

 tion. the context shows that it was little more) 

 that heat may be a mode of motion ; Des- 

 cartes affirmed the quantity of motion in 

 the world to be constant ; Newton nearly 

 gave expression to the complete theorem ; 

 while Rumford's and Davy's experiments 

 suggested, though they did not prove, 

 the equivalency of mechanical and ther- 

 mal energy. Again, the discovery of vol- 

 taic electricity, and the marvellous de- 

 velopment of knowledge, in that field, 

 effected by such men as Davy, Fara- 

 day, Oersted, Ampere, and Melloni, had 

 brought to light a number of facts which 

 tended to show that the so-called ' forces ' 

 at work in light, heat, electricity, and 

 magnetism, in chemical and in mechani- 



