A HISTORY OF SCIENCE 



come heat, motion must cease to exist as motion, 

 whether simple, or vibratory, as in the case of light 

 and radiant heat, etc. 



"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 disap- 

 pears again, calling forth unceasingly a great quan- 

 tity of heat; and, inversely, the steam-engine serves to 

 decompose heat again into motion or the raising of 

 weights. A locomotive with its train may be com- 

 pared 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." 



Mayer then closes his paper with the following de- 

 duction: "The solution of the equations subsisting be- 

 tween falling force and motion requires that the space 

 fallen through in a given time e. g., the first second- 

 should be experimentally determined. In like manner, 

 the solution of the equations subsisting between fall- 

 ing 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 



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