N egatively Electrified Corpuscles hy Hot Bodies. 257 



Then we have, since X = VH, where V is the velocity of 

 light, 



dt 2 dt \ dt) 



-Be*-* 



(1) 



d 2 !l n 





(2) 



dt 2 





d 2 z TT dx d 2 t TT dx 



m d¥ =Ee dJ> m dF= Be dt> ■ 



. . . 



(3) 



where ^==z — Yt. 



Let us first take the case where a pulse of constant electric 

 force is passing over the corpuscle. Then if x, z vanish when 



£=0 and u and w are the initial values of •=- and ~. we get 

 from (1) and (3) dt dt 



2= \t-\ — -ry (1— cos cot) H smcot, 



e n v ' co 



and 



-^ =Y + u sin cot+ (« — Y) cos cot, 



where cb=zHejm. 



Thus if the pulse lasts for a time T, long enough to make 

 ft)T large, the corpuscle will be set in motion in the direction 

 in which the wave is travelling, and the average velocity of 

 the corpuscle will be that of the wave. Now 



ft)T = THe/m = 10 7 .T.H; 



thus if T the time the pulse takes to pass over the corpuscle is 

 large compared with 1/1C 7 H seconds, the corpuscle will be 

 shot forward with great velocity in the direction in which the 

 pulse is travelling. If coT were small, the velocity acquired 

 by a particle starting from rest would be JVo> 2 T 2 . 



Let us now take the case of a periodic disturbance ; let H 

 be given by the equation 



H= A eos~(Vt- Z ) =Acos^?. 

 A A 



Equations (I) and (3) become 



cFx . 277- v c/f ,. % 



"ST— Amob x- c ;*' ••••(*) 



oT-t A 27r v dx 



m d? = Aecos T ? -^ ; • • • • (°) 

 Phil. Mag. S. 6. Vol. 4. No. 20. Aug. 1902. S 



