688 



followed out in ^12 improbable, namely that the mercury below 

 the vanisliing poiut comes away from the i>lass or at least does not 

 i>,ive oil" heat to it at a difference of temperature. The correspond- 

 ence of the disappearance of the resistance in the tin wire with 

 sentinel wires and in the mercury thread is explained most simply 

 by assuming a local rise of temperature in both, while for both 

 below the vanishing point the same opportunity i-emains for giving 

 off heat, but does not take place owing to absence of rise of 

 temperature. 



Here, therefore, the "bad places" mentioned in § 11 ^comp. § 12«, 

 note 1 p. I'JS) would again remain as the sole explanation. It is 

 how^ever suspicious that in the coil of lead wire at 1°.6 K. 56 

 amp./mm', was found as the threshold value, while with lead in 

 a vacuum 270 amp./mnr. at 4°. 26 K. was reached without a trace 

 of potential phenomena. 



Finally we point out that the threshold values of current density 

 far below the vanishing point in the wires of the three different 

 metals differ very little. We found for the highest limit of the 

 possible micro-residual resistance determined by the threshold value 

 in proportion to that at the ordinai'y temperature 



with mercury —^ <^ 2.10— i o 



2730 A 



w 

 tin -J--^< 6.10-10 



2730 A 



lead ^■1^< 0.5 10-10 



w 

 2730 A 



In view of so much correspondence and such regularity of the 

 character of all the potential phenomena, it still remains doubtful 

 v;hether besides the distui'bances which we have adduced to explain 

 them, there may not be at the bottom of them peculiarities in the 

 movement of the electrons, which may be more clearly revealed by 

 the experiments indicated in y. 



Having completed the series H of my experiments with liquid 

 helium I wish to express my thanks to Mr. G. Holst, assistant at 

 the Physical Laboratory, for the devotion with which he has helped 

 me, and to Mr. G. J. Flim, chief of the technical department of the 

 ci-yogenic laboratory, and Mr. 0. Kessrt,ring, glassblower to the 

 laboratory, for their important help in the arrangement of the 

 experiments and manufactuiing of the apparatus. 



