281 



amp. with a tiekl of J 89 gauss, the satne as used witli the other 

 experiments, whereas the main experiment at the same temperature 

 and inducing tield had given 0.4 amp. 



More satisfactory was the experiment in which first a current is 

 produced in the coil — analogous to the currents in resistance-free 

 paths as imagined by Wrber for tiie explanation of diamagnetism — 

 and then destroyed by the removal of the field: an almost comjilete 

 compensation was obtained in this case. The expei iment was made 

 with a field of 189 gauss. This result is of special importance as it 

 practically disposes of the supposition mentioned in the previous 

 paper as possible, although very improbable, that magnetic properties 

 of the material of the coil might play an important part in the 

 phenomena. 



The current in the coil changes with any new magnetic field 

 applied and with any further change in it, or with any change of 

 position relatively to the field. In this respect the influence of the 

 earth-field may be noted. The current in the coil, when placed with 

 its windings at right angles to the meridian, will assume a slightly 

 smaller value in the one position North-South and a somewhat larger 

 value in the opposite position Sout-North than in the position East- 

 West, which is practically the position in which the experiments 

 were made. In our experiments this action was however too small 

 to be taken into account considering the accuracy which could be 

 attained at the most. 



It may be observed that our conductor carrying its current in the 

 absence of an electromoti\'e force, when undergoing the relatively 

 small action of the field of the earth, is analogous to the Ampère 

 molecular currents (in the form of circulating electrons) which play 

 a part in Langevin's theory of magnetism, when they experience a 

 diamagnetic action on being brought into a field, in accordance with 

 LoRENTz's theory of the ZEEMAN-efFect. 



^ 8. The e.cpenments repeated ivitli the circuit open. 



So far it has been constantly assumed, that the magnetic properties 

 of the material of the coil play but a secondary part in the pheno- 

 mena observed, when the experiments were arranged so as to 

 produce a permanent current. This view was based firstly on the 

 difference in the results with the windings parallel and perpendicular 

 to the field dni-ing the cooling in the field and secondly on the 

 compensation found on a[)plying and removing the field after the 

 conductor had already been cooled to helium-temperature. Further- 

 more that the part of the effect which is independent of the circu- 



