2ft2 



laliiig current must bc ascribed (o the lead itself, was to be inferred 

 fi'oiu- tlie fact, that the current is quenched, as soon as the tempe- 

 rature of the coil rises somewhat above the boiling point of helium 

 and passes the point which, as being the vanishing point for lead, 

 has a special physical meaning for this substance. 



In order to obtain further information as to the part of the 

 phenomenon which depends upon the material itself, the experiments 

 were repeated after the lead- wire connecting the ends of the coil 

 had been cut, so that the circuit was no longer closed (apart from 

 possible short-circuits in the coil). 



This time the experiments with the exception of one could only 

 be [)erformed at 4.°25 K: still there does not seem to be any objection 

 to applying the results for the explanation of the irregularities which 

 had been left unexplained in the main experiments, although these 

 had been mostlj' carried out at a lower temperature. 



In all the experiments a certain residual effect remained, which 

 was reduced to about one tenth when the windings were parallel 

 instead of at right angles to the held and in the latter case was 

 fairly well independent of the lield. The amount of this effect cor- 

 responded to a moment which was equivalent to a current of 0,05 

 or 0,06 amp. in the closed circuit. In one of the experiments, the 

 only one in which the temperature was lower than 4.°25 K., viz. 

 about 3° K., the moment was estimated to be equivalent to as 

 much as 0,07 amp. The effect with the circuit open is thus very 

 much smaller than in the main experiments. The share boin in the 

 effect by the frame of the coil and the lead independently of closing 

 the circuit may therefore be put at less than ^ \ of the total effect 

 in the main experiment. 



As a check on former experiments the following additional expe- 

 riments were made with the coil with the lead wire cut. 



In the first place at the ordinary temperature after joining up to 

 a ballistic galvanometer the induction was measured arising from 

 putting on or taking off the field with the windings in the position 

 in which they were supposed in the previous experiments to be 

 parallel to the field. The induction was found to be Y^^ of the effect 

 in the position at right angles to the field. This observation may 

 contribute to the explanation of the residual effect obser\'ed in the 

 expei'iments in helium in the position with the windings parallel to 

 the field. 



In the second place a known current was sent through the coil 

 and its strength measured by the same method as used in deterniining 

 the moment of the experimental coil in the experiments with the 



