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Nor do these facts rest upon physical evidence alone. 

 Chemistry teaches that thought-force, like muscle-force, 

 comes from the food ; and demonstrates that the force 

 evolved by the brain, like that produced by the muscle, 

 comes not from the disintegration of its own tissue, but 

 is the converted energy of burning carbon. 3s Can we 

 longer doubt, then, that the brain, too, is a machine for 

 the conversion of energy ? Can we longer refuse to be- 

 lieve that even thought is, in some mysterious way, cor- 

 related to the other natural forces ? and this, even in 

 face of the fact that it has never yet been measured ? 3 6 



I cannot close without saying a word concerning the 

 part which our own country has had in the development 

 of these great truths. Beginning with heat, we find that 

 the material theory of caloric is indebted for its over- 

 throw more to the distinguished Count Rumford than to 

 any other one man. While superintending the boring 

 of cannon at the Munich Arsenal towards the close of 

 the last century, he was struck by the large amount of 

 heat developed, and instituted a careful series of exper- 

 iments to ascertain its origin. These experiments led 

 him to the conclusion that " anything which any in- 

 sulated body or system of bodies can continue to furnish 

 without limitation, cannot possibly be a material sub- 

 stance." But this man, to whom must be ascribed the 

 discovery of the first great law of the correlation of 

 energy, was an American. Born in Woburn, Mass., in 

 1753, he, under the name of Benjamin Thompson, 

 taught school afterward at Concord, N. H., then called 

 Rumford. Unjustly suspected of toryism during our 

 Revolutionary war, he went abroad and distinguished 

 himself in the service of several of the Governments of 



