ON MATTER AND FORCE. 33 



Electricity, wrote (Exp. Besearches, vol. ii., 

 p. 103) : " We have many processes by which 

 the form of the power may be so changed that 

 an apparent conversion of one into another 

 takes place." " But in no case is there a pure 

 creation a production of power, without a 

 corresponding exhaustion of something to sup- 

 ply it." 



Mr. Grove, in a lecture on the Progress of 

 Physical Science in 1842, says : t( The present 

 tendency of theory seems to lead to the opinion 

 that all these affections (of matter) are resolv- 

 able into one namely, motion ;" and : " Light, 

 heat, electricity, magnetism, motion, and che- 

 mical affinity, are all convertible material affec- 

 tions. Assuming either as the cause, one of 

 the others will be the effect. Thus heat may 

 be said to produce electricity, electricity to 

 produce heat, magnetism to produce electricity, 

 electricity magnetism, and so of the rest. . . . 

 We must humbly refer their causation to one 

 omnipresent influence, and content ourselves 

 with studying their effect, and developing by 

 experiment their mutual relations." 



In 1843, in a course of lectures on the 

 Correlation of Forces, he says : " The view 



D 



