676 



y. Besides lead and tin, amalgamated 

 tin foil was investigated. We examined a 

 lajei' of it spread out on a mirror glass, 

 in wliicli layer grooves were made in the 

 manner shown in tig. 8. In helium boiling 

 at atmospheric pressure, it appeared to 

 have lost the ordinary resistance (2.3 i2 

 at 290° K.). At 4°.29 K. we found 0.12 amp. 

 for the threshold value of the current, and 

 a potential of J.3. 10-<^ volt, at 0.30 amp. 

 19.8. 10- e volt, and at 0.363 amp. 34.6. 

 10-f' volt. 



It is worth noticing that tliis amalgamated 



tinfoil becomes more easily superconducting 



than either tin or mercury. Pei'haps the soft 



tin-amalgam, though a solid solution (of 



mercury in tin), has this property. This 



Fig- 8 ^\- 9 would only need to become a continuous 



whole in order to provide a nonresisting path for the current beside 



that of the free mercury ^comp. (§ 9) or tin lliat might be present 



in the tin foil. 



HJI 



bM, 



§ 14. Further investigation of tin. The further investigation of tin 

 and lead does not form by any means a complete whole yet. Several 

 of the measurements we had in view were failures, so that the 

 results attained are very disconnected ; nevertheless, in connection 

 with our experiments with mercury, I think them worth communicating. 



a. Methods of working the tin. In tlie previous ^ we said that 

 working the tin into a spiral shaving did not interfere with the 

 sudden disappearance of the resistance. What is of even more 

 importance is that the rolling out of the wire to a thickness of 

 0.01 mm. has not any intluence upon the super-conducting state 

 either, so that we may feel confident that a very thin nonresisting 

 tinfoil could be made ^). 



We must remark that in working tin, heating must be avoided. 

 The increase of hardness which is caused in the drawing of metals 

 by the compression and stretching, which is accompanied by an 



1) The resistance of commercial tin foil, pasted on glass and cut out as in 

 fig. 9, appeared not to become zero. 



