IM) 



for liis help. A paper on liie subject will be published shortly. It 

 appears from this that the effect which (see fig. 3, and in detail 

 fig. 4) changes little with tfje fall from 4°.25 K to 2° K, increases 

 considerably with the fall from 14° K to 4°, 25 K. 



It is worthy of notice that the sudden change differs considerably 

 in magnitude with l^hxii J^nd Pbf\. Possibly there is a difference 

 in the nature of the lead in the two coils. In fact at 20° K 



^^^ = 0.0284 and ~^-^ = 0,0274. 



w w 



Amongst the ditfei'ent questions that arise, one is whether a lead 

 wire n)ight be constructed in which the magnetic resistance, remaining 

 zero as far as the threshold value of the field, will further gradually 

 increase with the field from the value upwards. 



so 



'lO 



iO 



t 



^' 



soo 



w: 



i5ao iooo 



Fig, 4. 



1500 



3i\n 



35öJ (la\ii>'i. 



There is no doubt that the phenomenon discovered here is con- 

 nected with the sudden appearence of ordinary resistance in the 

 supra-conductors at a certain temperature. The analogy between the 

 influence of heating upon the resistance and that of the introduction 

 of the magnetic field, is so far complete. 



One would be inclined to assume that an energy of I'Otation 

 determined by the magnetic field might be simply added to the 

 energy of the irregular molecular motion. If, in the production of 

 the obstructions which determine the resistance we have to do with 

 dissociations in the sense, that movements of electrons in certain 



