EQUIVALENCE OF HEAT AND MOTION. 257 



But just as little as the connection between falling force 

 and motion authorizes the conclusion that the essence of fall- 

 ing force is motion, can such a conclusion be adopted in the 

 case of heat. "We are, on the contrary, rather inclined to 

 infer that, before it can become heat, motion whether sim- 

 ple, or vibratory as in the case of light and radiant heat, &c. 

 must cease to exist as motion. 



If falling force and motion are equivalent to heat, heat 

 must also naturally be equivalent to motion and falling force. 

 Just as heat appears as an effect of the diminution of bulk and 

 of the cessation of motion, so also does heat disappear as a 

 cause when its effects are produced in the shape of motion, 

 expansion, or raising of weight. 



In water-mills, the continual diminution in bulk which the 

 earth undergoes, owing to the fall of the water, gives rise to 

 motion, which afterwards disappears again, calling forth un- 

 ceasingly a great quantity of heat ; and inversely, the steam- 

 engine serves to decompose heat again into motion or the 

 raising of weights. A locomotive engine with its train may 

 be compared to a distilling apparatus ; the heat applied under 

 the boiler passes off as motion, and this is deposited again as 

 heat at the axles of the wheels. 



We will close our disquisition, the propositions of which 

 have resulted as necessary consequences from the principle 

 " causa a3quat effectum," and which are in accordance with 

 all the phenomena of Nature, with a practical deduction. 

 The solution of the equations subsisting between falling force 

 and motion requires that the space fallen through in a given 

 time, e. g. the first second, should be experimentally deter- 

 mined ; in like manner, the solution of the equations subsist- 

 ing between falling force and motion on the one hand and 

 heat on the other, requires an answer to the question, How 

 great is the quantity of heat which corresponds to a given 

 quantity of motion or falling force ? For instance, we must 

 ascertain how high a given weight requires to be raised above 



