MECHANISM OF NATURE 



ought to find the law of series which undoubtedly 

 underlies the increase of atoms from the lightest to 

 the heaviest. 



PROPOSITION XVII. 



Heat is an increase of the magnitude of inter- 

 stices between particles of substances, against 

 the opposition offered by gravity and the inter- 

 locking of solids. 



There are many changes produced by heat in 

 material around us, that we may compare wit 1 " 1 

 each other, and with changes produced in the same 

 material by other manifestations of force. 



The foremost of these changes is the expansion, 

 of every known substance, by heat, and the subse- 

 quent contraction by the withdrawal of heat. 



And there is an equivalent between heat and 

 expansion so perfect that our measurement of heat 

 is based upon it. 



The theories of the nineteenth century have re- 

 duced heat and other forces to wave motion and 

 have found a solution of the mystery of the dif- 

 ferences between the several forces in the length 

 and rapidity of the waves. 



But all waves are composed of material, and 



back of the waves must be the force that moves 



the waves, and the waves must depend in length 



of motion and rapidity of motion, not on the waves 



150 



