460 POPULAR LECTURES AND ADDRESSES. 



"cannot produce motion simply by consuming the 

 " heat of a hot body." 



<l When we produce motive power by the passage 

 " of heat from the body A to the body B, is the 

 " quantity of this heat which is delivered to B (if it 

 ' is not of the same amount as that taken from A, 

 " if a part is really consumed to produce motive 

 " power) the same, whatever be the substance 

 " employed [in the ideal engine] to realise the 

 " motive power ? " 



" Could there be possibly a means [or substance] 

 " for causing more heat to be consumed in pro- 

 " ducing motive power, and, therefore, less to be 

 " delivered to the body B ? Would it be possible 

 " even to consume the whole heat taken from A, 

 " without the necessity of delivering any heat to, 

 " B ? If tliis were possible we could create motive 

 "power without fuel, and simply by destruction of 

 "some of the heat of bodies." 



In these last words (which I have given in 

 italics) we have from the founder of our theory of 

 the steam-engine and other heat motors, and the 

 profouiulcst thinker in thcrmodynamic philosophy 



