683 



Further, iTieasureirieiits were made with lead wires phiced in a 

 vacuum, (he object of whicli is obvious by § 12. The apparatus 

 wliich served for (his consists (see fig. 10 and fig. 11, face view and 

 diagram of d with detail figures) of a glass reservoir immersed in 

 liquid helium, carried by a long narrow glass tube fixed into the 

 lid of the cryostat. The resei-voir d can be evacuated through the 

 tube 6' (the tap a allows it then to be connected to a tube filled 

 with charcoal which is immersed in liquid air) ; through the indicator 

 gauge b we can make suie that the apparatus is not cracked in 

 cooling. 



In the apparatus shown in the fig. there are two lead wires (see 

 diagram); we were only able to do the measurements with one. 

 Four short tubes are blown into the upper part of the reservoir 

 to receive the lead wires (see detail figures) ; upon these tubes after 

 platinizing and copperplating caps are soldered with tin into which 

 the thicker top ends of the wires are soldered with WooD-metal ^). 



Rolled out lead wires are fastened to the wires that project from 

 the covers, and run down along the reservoir, insulated from each 

 other with silk and then up again through the liquid helium. 



We found with a part of the wire of Table XI : 



The experiment is incomplete as the threshold value was not 

 reached. 



We made similar apparatus with tin wire; the observations with 

 tin in vacuo have, however, not succeeded yet. 



§16, Remarks in connection with the experiments with tin and lead, 

 a. Our results with tin and lead make it seem probable that 



-) It is not possible to solder tin wires into the covers with Wooometal : as 

 coming in contact with the tin the melted WooD-metai, as it seems, penetrates 

 by capillary action amongst the tin crystals which makes the wire brittle and 

 break in two. The tin wires must therefore be melted to the tinned covers, which 

 is possible, by their being provided like the lead wires with sealed on thicker ends. 



