. il II "KM M'-II.'N '2.1 



is rotated in a mat^iietir ti-M a o-rtain ex|eniiitiire of 



energy is necessary on account of what ha* been called 

 ram This energy is, no doubt. -vent ually dissipated 

 in the form of heat, hut thi- tart !'- not warrant us in 

 classing it under heat in the performance of an 

 motor. We must know whether t >f hysteresis is 



to oppose the moti-ii 



Now, although the motions concerned in the expemli- 

 tiii-.- of .!!!_'} l>v hysteresis can be described as \-\\\\! 



* those of molecules,' and as being ' so small individually 

 that they quite escapr all <ir mot hods of observation, ' yet 

 we know that energy sp- nt in hysteresis is spent in 

 coming a ili-tinit<* reAistanct* to motion, a resistance that 

 can be meastiivd. I {no* w- rondud*- that hysteresis 

 most be classed as an e.xp-iulitureof energy in tin- t- rm of 

 work. 



Tin 'n may at first si^ht ap|x>ar to be a contra- 



n of Cli-rk Maxwell's -tati-ment tliat 'when thr 



motions and displacements are those ot \ :-ii.!.- IH-H,^ con- 

 si-tinj^ of great numlH-rs of molecules moving top-th-r. the 

 communication of energy is called work,' for we could 

 hardly dew-ril*- the phenomena of hv-N r.-sjs in ^nrh t.-rms. 

 rk Maxwell, II..W,-V.T. furesaw the possibility of 



onr senses being sharpen*d to *uch a degree that u ,- 



'ions of the inolivules as easily as we 

 now trace those of larger bodies.' The "fmrhft of 

 IVofetSUl Kwing and others have enabh 

 the case of hysterejnn, so that we can actually trace th>- 

 I* ot' the molecules accompanying this phenomena as 

 as we can trace those of larger bodies, and measure 

 the resistance to motion that in offrntl l>y tli<> <-<>ml>Jn'><| 

 n of all tin- molecule* in the iron. 



