34 CROONIAN LECTURES 



which I venture to submit to you in these 

 lectures is, that force cannot be annihilated, 

 but is merely subdivided, and altered in direc- 

 tion and character." " I will venture as an 

 opinion, founded after much consideration, that 

 science is rapidly progressing towards the es- 

 tablishment of immediate or direct relations 

 between all these forces." 



In 1843, Mr. Joule (Phil. Mag., vol. xxiii., 

 p. 442), on the Mechanical Value of Heat, says 

 that he shall repeat and extend his experi- 

 ments, being satisfied that the grand agents of 

 Nature are, by the Creator's fiat, indestructible, 

 and that, wherever mechanical force is ex- 

 pended, an exact equivalent of heat is always 

 obtained ; and he mentions the practical con- 

 clusions which may be drawn from the conver- 

 tibility of heat and mechanical powers into one 

 another. 



Mr. Faraday, in a lecture on the Conservation 

 of Force in 1857 (Researches, p. 454), says the 

 idea we have of the indestructibility of indi- 

 vidual matter is one case, and a most important 

 one, of the conservation of force ; and, in a 

 manuscript, he says : " Force cannot be anni- 

 hilated or created at pleasure. It cannot act, 



