SIS 



fl 



a combined view of the experimenis ot seC* 

 tions 9 and 11). The thread runs through a 

 tube, the lower [uxrt of which is of glass and 

 can be moved by means of a rubber-tubing 

 attachment at the top of tlie apparatus (fig. 1). 

 The coil was cooled to 2°.4 K. in a field 

 of 200 gauss by helium evaporating under 

 reduced pressure. The current vv^as again 

 produced through induction by removing the 

 field. When the compass needle with the com- 

 pensation-coils was arranged, as before, beside 

 the cryostat, a moment corresponding to a 

 current of 0.36 amp. was registered. The 

 observation was continued for an hour, in 

 which the diminution of the current in 45 

 minutes was within the limits of probable 

 error of the measurement (27o); after this 

 the circuit of the coil was cut through. The 

 needle of the compass fell back to a deviation 

 that corresponded to a current of 0.05 amp. 

 in the coil. Tiie ballistic galvanometer (wilh a 

 negligible self-induction and with 2000 Si in 

 the circuit) showed an electro-kirelic momentum 

 Li of 300000, from which follows with L=10\ 

 that a current of about 0.3 amp. tlowed in the coil. The remaining 

 moment is again the same fraction of the principal effect as was 

 observed previously, it was extinguished as soon as the coil was 

 pulled up above the liquid helium. The experiment proves conclusively, 

 that a current does really flow through the coil. 



§ 10. Further consideration of the monientwn produced in the 

 coil, when the circiut w not dosed. Persisting Yo\^Ck\}TJV-currents. In 

 the previous experiments the question arose in how far magnetic 

 l)roperties of the frame of the coil, which developed at the lowest 

 temperatures had an influence, and whether a part of the moment 

 that remained, when the coil, without the ends being connected, was 

 cooled and exposed to the field, was due to windings which were 

 short-circuited. For this purpose first of all a lube of brass, exactly 

 like that used as the frame of the coil, was cooled in the field. 

 It showed no residual magnetism. 



To get further light on possible short-circuits in the coil Phxn, 

 after it had been shown that cooling in liquid air did not alter 



3-t 



Proceedings Royal Acad. Amsterdam. Vol. XVII. 



2] 



-H-^ 



Fig 

 3.. 



