68 DAZZLED BY PRACTICAL POSSIBILITIES. 



of heat and mechanical power into one another, according 

 to the above absolute numerical relations.'' 



The chief of these conclusions, although implied rather 

 than explicitly stated in the paper, but explicitly stated 

 four years later, is that '• In the case of the steam- 

 engine, by ascertaining the quantity of heat produced by 

 the combustion of coal, we can find out how much of it 

 is converted into mechanical power, and rhus come to the 

 conclusion as to how far the steam-engine is susceptible of 

 further improvements. Calculations made upon this 

 principle have shown that at least ten times as much 

 power might be produced as is now obtained by the 

 combustion of coal." There is nothing absolutely wrong 

 in this conclusion, but it ignores the physical impossibility 

 of the conditions necessary to such realization ; conditions 

 not by any means understood at the time, nor till six years 

 after, and then as a consequence of Joule's discovery. Yet, 

 accepted in its simplicity, this conclusion was at variance 

 with all experience obtained throughout the career of the 

 steam engine. 



That, accepted in its simplicity, this conclusion should 

 have dazzled Joule for the time is not to be wondered at ; and 

 that so accepting it, he should have been led to call the 

 mechanical equivalent of heat, which he had discovered, 

 (; the mechanical value of heat," and use this as the title of 

 his paper, is not a matter of surprise. It was, nevertheless. 

 unfortunate after he had throughout his work been con- 

 sistently seeking equivalences, and on finding the crowning 

 equivalence, had not only treated it, but also considered it 

 throughout his investigation as an equivalence, that he 

 should have adopted another, and at least a questionable 

 expression, in the titles of his papers. 



