THE MECHANICAL EQUIVALENT OF HEAT. 



proved by some fact established beyond a doubt, we may ac- 

 cept it as true. 



Now we are taught by experience, that neither motion nor 

 heat ever takes its rise except at the expense of some meas- 

 urable object, and that in innumerable cases motion disap- 

 pears without any thing except heat making its appearance. 

 The axiom that we have established leads, then, now to the 

 conclusion that the motion that disappears becomes heat, or, 

 in other words, that both objects bear to each other an inva- 

 riable quantitative relation. The proof of this conclusion by 

 the method of experiment, the establishment of it in all its 

 details, the tracing of a complete harmony subsisting between 

 the laws of thought and the objective world, is the most inter- 

 esting, but at the same time the most comprehensive problem 

 that it is possible to find. "What I, with feeble powers and 

 without any external support or encouragement, have effected 

 in this direction is truly little enough ; but ultra posse nemo 

 obligatus. 



In the paper referred to (the first of Mayer's in the pres- 

 ent volume) I have thus expressed myself with regard to the 

 genetic connection of heat and moving force : 



"If it be now considered as established that in many 

 cases (exceptio confirmat regulam) no other effect of motion 

 can be traced except heat, and that no other cause than motion 

 can be found for the heat that is produced, we prefer the as- 

 sumption that heat proceeds from motion, to the assumption 

 of a cause without effect and of an effect without a cause- 

 just as the chemist, instead of allowing oxygen and hydrogen 

 to disappear without further investigation, and water to be 

 produced in some inexplicable manner, establishes a connec- 

 tion between oxygen and hydrogen on the one hand and water 

 on the other." 



From this point there is but one step to be made to the 

 goal. At page 257 it is said : " The solution of the equa- 

 tions subsisting between falling-force [that is, the raising of 



