18 



be sufücieiitly explained l>y assuming- that the attempt to place the 

 windings exactly parallel to the field had not succeeded. ^) 



If the initial value of the Held is higher than the threshold-value, 

 Mjj the i-esult is the same. This case is rej)resented in fig. 3. In 

 one experiment the initial field was 5000 gauss and the observed 

 magnetic moment corresponded to a current /= 0.7 amp. 



If the field through the. supraconducting coil is first put on and 

 subsequently put off again by bringing the excited electromagnet 

 to its position at the cryostat and then removing it, according to 

 the above reasoning fdisi-egarding the exceedingly slow diminution 

 with the time) no resultant current ought to remain, if no account 

 had to be taken of the threshold-value of the current. Indeed for 



the second period the relation i — i, e 



L 



— t' 



L 



holds, if L is 



the current obtained in the 

 first period during the gene- 

 ration of M^. This case will 

 be realized, if care is taken, 

 that the threshold-value of 

 the current is not exceeded, 

 li is represented in fig. 4 

 by the lines which give the 

 field Mi and the current 

 //, as functions of the time, 

 if during the increase of 

 M the threshold-current is 

 reached, the current will not 

 grow appreciably on further 

 rise of M ; from the moment, 

 that the increase of At stops, the current assumes the threshold-value 

 and stays there, until M begins to decrease : it then begins to fall 

 and becomes zero, before the field has disapi)eared ; on the further 

 diminution of the field, the current assumes the opposite sign and 

 (he resultant current will be that which has been formed at the 

 moment that M = 0, if it remains below the threshold-value, or the 

 threshold-current itself, if that is reached before M has disappeared. 

 In the latter case the curi-ent will exceed the threshold-value by 



') Tliis experiment bad been made some 'ays before the main experiment, alllioiigii 

 il liad nol been Ibe intention to make it witb Ibul position of the coil. So far it 

 has not been repealed. At the moment of making tbis first communication il liad 

 nol Iteen repeated. |lt lias been repeated since; again a rest was found. (Note 

 added in Ibe translation. Comp. (Jomm. N". 14()c)]. 



