CH. 11 -moss OF UNIFORM MO; J , 



peak of the energy thus communicated as being in the 

 form of heat. 



Professor Clerk Maxwell has stated tint -the only 

 difference between these two kinds of communication of 

 energy is that the motions and displacements which an* 

 concerned in the communication of heat are those of mole- 

 cules, and are 30 numerous, so small individually, and so 

 irregular in their distribution that they quite escape all 

 our methods of observation, whereas when the motions and 

 displacements are those of visible bodies consisting of 

 pivat numbers of molecule* moving toother, the com- 

 munication of energy is called work. Henoe we have only 

 to suppose our senses sharpened to such a d-^r.-e that we 

 : trace the motions of molecules as easily as we now 

 trace those of Urge bodies, and the di-tin-ti..n between 

 wrk and heat would vanish, for the communication of 

 heat would be seen to be a communication of eneiyy of the 

 same kind aa that which we call work.' ' 



If in ini|M.rtant to rememU-r that doinjf work implie- 

 overcoming a resisting force which ran U measured e\ 

 mentally. We know that we must be overcoming some 

 force when we pass a current tlir<iu</h a rheostat, 

 the dimensions of rate of communication of energy are 

 always the same, viz. a force multipli. -I by a distance and 

 d by a time; but in the case of heat we cannot 

 BMMurr th.- force experimentally, ami t .\erann..t 



say that we are doinp work. 



This becomes clearer if we express the r ,m- 



tn tin teat ing energy in term* of/ an<! /.. using the e*pi 



already found : 



r0-71/ watt ..(10). 



1 SeiMltyfe Paper,. TO). U. p. W. 



