19 



a very nmall amount fi-oiii the moment, that the threshold-value i8 

 reached, nntil M = 0. In tig. 4 this case is represented by the lines 

 which give the relation between the tield M^ and the current ia. 



All instance of the case represented b}' a is given by an experi- 

 ment, in which (he Held brought lo the cryostat was 400 gauss. A 

 strong resultant current was observed as in the case, when the coil 

 was first i'vee of current in the field of 400, was then made supra- 

 conductive and was finally charged with current b}' tiie removal of 

 the field. An instance approximately corres'ponding to case h was 

 obtained, when the same experiment as a was carried out with a field of 

 190 gauss. Even in this case the compensation was not quite complete 

 and a little more favourable, when the field was made to approach 

 slowly, than with a rapid approach. 



With a rising field account has to be taken also of the compli- 

 cation arising out of the influence of the field of the current itself on 

 the threshold-values of the field and current. In fact this was not the 

 only feature in the experiments which could not be fully explained 

 yet: naturally as tiiej' were performed for the first time, the arrange- 

 ments were still imperfect ^). Taken together however the}' ma}' be 

 said to confirm the main experiment whicli shows that it is possible 

 in a conductor without electromotive force or leads from oul;side '^) 

 to maintain a current permanent!}' and thus approximately to imitate 

 a permanent magnet or better a molecular current as imagined by 

 Ampère. 



The electrons once set in motion in the conductor continue their 

 course practically undisturbed, the electrokinetic energy, represented 

 by Maxweli, by the mechanism of the rotating masses coupled to 

 the current, retains its value, the rotating fiy-wheels go on with 

 their velocities unchanged, as long as no other than supraconductors 

 come into play : the application of a small ordinary resistance 

 however stops the mechanism instantaneously. Although the experi- 

 ment mainly confirmed my deductions as to what had to be expected, 



1) One of the first questions still to be answered is, what part a possible magnetisation 

 of lead or brass may liave played in tlie phenomena : so far no proof has been 

 given, that this may be neglected. However, even now from the experiment, in 

 which the windings were parallel to the lines of force, we may draw the conclusion, 

 in view of the small amount of the action in that case, that the magnetisation 

 of the material of the coil can only play a very subordinate part compared to the 

 electromagnetism of the current, to which I have above ascribed the deviation of 

 the compass-needle. 



2) It may be mentioned here, that it will be possible, by a change of tempera- 

 ture of a small part of the conduclor. to insert a resistance in the circuit which 

 can be very delicately regulated without touching it, 



2* ■ 



