I BI )) 



of the resistance is belter preveiiled. Moreover in the new constrnc- 

 tion the pins //„i (see tig. 4), which siirronnded by gkiss tnbes ƒ/„,, 

 fit into the grooves //„g (see fig. 5, twice the dimensions of tig. 4), 

 prevent the cylinders and tlie snpporting ridges dnring tlie mounting 

 from shifting against eacli other, wliich would cause the wires to 

 break at the soldering places. Lastly, to prevent that (in consequence 

 of being cooled conduction of heat) water vapour condenses at the 

 place Avhere the wires t^, t^, t^, t^ leave the apparatus, the upper 

 part of the supporting rod k is made of glass. Therefore we have 

 fastened the cap k^^ to k^a '\7 means of hard solder, and fixed 

 according to Cailletkt's method (cf. Comm. N". Mb) the glass rod 

 kj to this cap. 



The connection of the ciyostat with the auxiliary apparatus agrees 

 in principle with that of Comm. N" 83 (especially Pis. IV and VI) 

 to which I refer for further details. The cryostat represented in this 

 paper replaces Cr on PL IV. At the place of E,vh' PI. IV, the 

 vacuumpump was exhausted by a smaller one, which displaces 

 20 M' an hour. This forces the oxygen at normal pressure through 

 a solution of caustic soda in order to keep back the oil carried 

 along from the vacuumpumps. The small vacuumpump also replaces 

 AC of PI. IV (the lead E,vh' terminates into it at F34, the tube Avith 

 caustic soda replaces D^ on PI. IV). The oxygen, after having 

 bubbled through the caustic soda solution, can without fear of 

 explosion be compressed by a Brotherhood compressor arranged as 

 described in Comm. N". 51, Sept. '99, and lubricated with glycerine 

 (cf. Comm. N" 83 IV). It thus replaces Ri/C on PI. IV of N°. 83. 



The admission of liquid oxygen is sometimes effected by directly 

 syphoning over liquid oxygen from a vacuum glass into the cryostat. 

 As a rule, however, compressed oxygen from a cylinder is used 

 and as generally we have a large quantity of cylinders with com- 

 pressed oxygen in store, it is supplied from another reservoir than 

 that in which the sucked off oxygen is compressed (in that case the 

 connection RR-D^ of plate IV, Comm. N". 83, does not exist). The 

 oxygen liquefies in a cooling tube immersed in liquid air (the 

 nitrogen in CS of PI. IV Comm. W. 83, is replaced by oxygen, 

 the oxygen by air) and thence passes through a (see the annexed 

 plate) to the cryostat. 



As to the way to keep the temperature constant, the only alteration 

 from what has been laid down in Comm. N". 83 is that with high 

 vacua the oil manometer is no longer used and we regulate only by 

 means of the cock Y^, (Comm. N". 83) being guided only by signals 

 according to the readings of the resistance thermometer. The mean 



