APPENDIX A. 223 



the source of our knowledge in regard to the na- 

 ture of bodies, their form, their forces; to see what 

 the primitive notions are, to see from what im- 

 pressions they are derived ; to see how one is raised 

 successively to the different degrees of abstraction. 



Is heat the result of a vibratory motion of mole- 

 cules ? If this is so, quantity of heat is simply 

 quantity of motive power. As long as motive 

 power is employed to produce vibratory movements, 

 the quantity of heat must be unchangeable; which 

 seems to follow from experiments with the calo- 

 rimeter; but when it passes into movements of sen- 

 sible extent, the quantity of heat can no longer 

 remain constant. 



Can examples be found of the production of 

 motive power with actual consumption of heat ? 

 It seems that we may find production of heat with 

 consumption of motive power (re-entrance of the 

 air into a vacuum, for example). 



What is the cause of the production of heat in 

 combinations of substances? What is radiant 

 caloric ? 



Liquefaction of bodies, solidification of liquids, 



