28Ó 



also taken, that the current did not rise above the value at which 

 no further change had been observed at 4°. 25 K. The current was 

 therefore raised to only 0.22 amp. (approximate value calculated 

 as before from the observed magnetic moment of the coil), so that 

 the supply of a fresh quantity of lielinm would probably not have 

 the disturbing effect which had been noticed in the previous expe- 

 riment. The temperature used was 2° K. lu the beginning again a 

 fall of current was noticed which must however be considered as 

 uncertain, inter alia owing to the possibility of the changes of shape 

 of the apparatus and the change of zero of the needle not having 

 been sufficiently eliminated yet in these observations. In the three 

 hours subsequent to the initial period no further diminution was 

 observed, the last observation even giving a small increase. Still in 

 this experiment the accuracy could not be considered greater than 

 about 27o of the measured moment and, as it was found impossible 

 to continue the experiment beyond three hours, again only an upper 

 limit for the change could l)e established, to be put at about Vs 7o 

 for current and induced magnetisation combined. Taking all the expe- 

 riments together it may be considered as probable, that the change 

 of the current is less than 1 "/„ per hour which raises the time of 

 relaxation to above 4 days. 



§ 6. Upper limit of the residual micro-resistance according to these 

 experiments. So far no contradiction has arisen in reasoning on the 

 assumption of the existence of a residual micro-resistance which 

 below the threshold-value of the current again obeys Ohm's law. 

 Oil this view the upper limit of this micro-resistance for lead, which 

 in Comm. N". 133 was placed at 0,5 10-^^ of the ordinary resi- 

 stance at 0\ can now on the basis of the above observations be 

 moved further back to about 0.3 lO-^^ or 0.2 10— '^ of the resistance 

 at the ordinary temperature. 



§ 7. Some of the control-experiments repeated. In the previous 

 paper a few other experiments beside the main experiment were 

 described : some of these ha\'e now also been repeated. 



Again we did not succeed in conducting the experiment in which 

 the windings are placed parallel to the field, the coil cooled below 

 the vanishing-point while in the field and then the field removed 

 iu such a manner, that the compass-needle, when brought near the 

 ciTOstat after removal of the electro-magnet, did not show any 

 deflection. After the action of a field of 400 gauss at 4°. 25 K. a 

 current of 0.1 amp. was found in the coil. This would give 0.045 



