48 Mr. S. B. McLaren on the 



magnetic field *. There can, therefore, be no kinetic theor y 

 o£ induced magnetization. This is one more argument 

 against the ultimate validity of ordinary mechanics. 



■${dN) = (dK)t-(dN) (13) 



The suffixes denote the actual values of dN at times t and 

 in the motion as disturbed. Remembering (9) the right- 

 hand side of (13) is seen to be the difference in value of <ffi 

 due to the disturbance. From (13) 



i(dS) = (' ^(dS)dt (14) 



The quantity 



is zero in the undisturbed motion 



7 



a 

 dt 



or 



**<*>-* Xs-fc it)™- 



In (15) the right-hand side is zero when the motion is not 

 affected by radiation, but if the equations of motion are 



given it can be expressed as a linear function of ohn,—f^, &c. r 



which are functions of the time, and of a 1} a 2 > &o- These 

 equations of motion are taken to be 



_ r =/;.(>!, X 2 , . . . Xn) f 2 (-^X'rm + XmXrm)' (16) 



dot 

 The terms in u m and ——- must of necessity be linear if 



the absorption is to be proportional as in fact it is to the 

 intensity of radiation. %V»o and X(r,m) are functions of 



X V> X 2-> - • X n' _ . dH 



The rate of increase of the material energy _— is (riven 

 by dt ' to 



dH r = n dHdxr 



dt ~ r —\dx r dt 

 * See also W. Voigt, Ann. d. Phys. ix. p. 115 (1902). 



