700 



Fig. 1. 

 Each sliaip peak corresponds to a reversal of the magnetisation 

 and we have lor each of them 



ƒ 



edt=± T/. I, 



(8) 



Let the origin / = coincide with a point in Fig. 1, wiiere the 

 current passes from the negative to tiie positive direction. Then we 

 may write 



i = A sin Vit, (9) 



and 6 may be developed in a series 



6 



S B cos n (o t 



(10) 



Of tliis series the first term only need be considered here, as the 

 effect corresponding lo it is tlie only one that is mnltiplied by 

 resonance, so that the otiier terms have no sensible inflnence on the 

 motion of the cylinder. Now, multiplying (10) b}' cos vit and inte- 



grating over a full period T^ — we find 



ƒ 



'''' rr 



6 cos (Jit dt ^rz— B,. 



On tlie left hand side is ditferent from only in the very small 

 intervals at ^ = and t = -. For the first of these we may put 



tubes were connected in such a way, that a current passing through them flowed 

 round the tubes in opposite directions. 



Under these circumstances, th- current induced in the windings is exactly pro- 

 portional to — , the demaanetizins action of the poles of the iron bar being 

 ' dt 



eliminated, as well as the induction due to the field of the coil K. Tiie graph 



dl 

 for the induced current, and therefore for - - or 8 was obtained by means of an 



dt 



oscillograph of Siemens and Halske. The alternations of the current i, repre- 

 sented by the sinusoid, were registered in the same way. 



