ELECTRICAL PROPERTIES OF CONDUCTORS 591 



TABLE III 

 Potential difference and current density in mercury. 



The investigations on the effect of powerful magnetic fields 

 were more easily carried out with lead or tin wires than with 

 mercury, and indeed if any practical application of the 

 phenomena is possible it will have to be with wires which 

 can be wound into close coils. The results with lead and tin 

 are given in the accompanying table for two temperatures, 

 in such case. With lead, however, both occur in the super- 

 conductive region, but with tin the critical value 3*8° K. occurs 

 between. 



TABLE IV 

 Effect of magnetic field on resistance. 



Hence it has the same kind of effect as that of heating the 

 conductor or of too large a current. In the case of lead the 

 change occurs at considerable fields, and does not preclude 



