678 



sentinel wires Wsa ^^nd Wsb^) of 0.8 in. length and about 0.02 mm^ 

 section, wound round a glass tube and insulated with silk. We found, 

 (Febr. 1913)^): 



With a coil of 252 windings of tin wire insulated by picëin (see 

 § 16) of 0.014 mm^ section, (with pieces of 0.02, 0.012 and 0.03) 

 and 79 Si resistance at ordinary temperature 290° K., the disappearance 

 of the resistance was followed, at three different current strengths 

 as in § 8 was done with mercury. We found : 



1) The object of the sentinel wires was the same as in VII § 6. We had namely 

 calculated on sending much stronger currents through than we actually did, and 

 on that supposition it was necessary to make sure that no Joule heat penetrated 

 to the wire from elsewhere. 



2) In one of the sentinel wires WsA there is obviously a thinner place which 

 causes locally a much greater current density than the mean. Probably the same 

 case occurs here as in the experiments with mercury in Table IV", but here the 

 disappearance of the resistance at lower temperature makes it improbable that the 

 tin wire should be interrupted by a foreign resistance. 



