large, thé current (Fig. 2) on M diminishing to will reach the 

 tijresliold-valuo, belonging to the temperature of the experiment, and 



Fig 2. 



Fig. 3. 



after the incluclion lieing completed will continue, while only after 

 a lonii' time /' accord ino' to the relation 



i = ID<^ 



in 



accordance with the large value of the time of relaxation 



an appreciable diminution of i will be observed. 



The case, that the initial value of M is above the threshold-value 

 of the |>rodiiction of resistance J//;, is represented in Fig. 3, which 

 after the foregoing needs no special elucidation. The result is ap- 

 parently again dependent oji the threshold-value of the current (see 

 also one of the experiments in § 4). 



As appears froni tlie values given above an initial field much 

 smaller than M d was sufficient in our experiment. 



According to the above calculation it was to be expected, that 

 the examination of the magnetic action of the coil could be per- 

 formed with a simple compass-needle brought near the crjostat. 



§ 4, Details of the observations. The result proved the correctness 

 of the discussion contained in the previous sections. The field was 

 taken at 400 gauss. In 10 seconds it was reduced to 200 gauss 

 and i in mediately afterw^ards the electromagnet was rolled away in 

 5 seconds. The compass-needle which was then placed beside the 

 cryostat to the East of it on a level with the coil and at a distance 



