• G30 ) 



fvlindrical jacket N'^ is [)laeed resting against the latter by means 

 of an india-rubber ring JSF\. Two cylinders J!^\, JSF\ of nickel-paper 

 serxe to diminish radiation, especially in the direction of the delivery 

 tube. 



As mentioned the frame which kee}>s the protecting cylinder in its 

 place is fastened to the cover. For a complete explanation of the 

 letters and parts of both this and the stirrer reference may be made 

 to § 4. Further we may note that g^ is fastened with silk cords 

 to ^', and this again with silk cords to the cover N\o, while S,\ is 

 supported by the glass tube §, fitting onto the pins sV 



The three threads Xi <>Ji ^vhich the stirrer hangs are led directly 

 through the three india-rubl>er tubes /'gj, connected hermetically to tubes 

 soldered onto the cover and fitting hermetically onto the threads at 

 XV^^ to the brass disc yd.^ -^ntl rod /'«^ which is connected by a 

 small cliain yï^, passing over a pulley x'ee to the motor by means 

 of a steelwire. The arm of the motor may be adjusted to different 

 throws, Avhile velocity of rotation can be regulated by means of a 

 rheostat. 



The mounting of the apparatus is very simple. The stopper with 

 the measuring apparatus is placed into the tube .V'„j of the cover, 

 to which all the auxiliary apparatus has been connected, then the 

 vacuum glass is slid into the india-rul)ber ring which is also connected 

 to the cover and is fastened there by means of tightening l)ands. In 

 order to secure an airtight (it the india-rubber on the metal and on 

 the glass has been coated beforehand with a solution of indiarubber 

 in benzine. 



With a view to the description given in III the operations for 

 the adjustments at given temperature recpiire amplification only in a 

 few points. In the case considered here, the evaporated gas was led 

 back through the exit tube to the gasholder or to the large exhausted 

 reservoir of the ethylene circulation in the cryogenic laboratory 

 (Comm. 14, Dec. '94) whence the ethylene \xü.<i further condensed 

 into the condenser immersed in methyl chloride. As described in 

 Comm. 14 the circulations of the cryogenic laboratory have been so 

 arranged that they may be used at any time. Besides the reservoirs 

 that have to be exhausted, a permanent part of the circulation consists 

 in branched tubes with cocks as shown on plates I and IV. The 

 cryostat had only to be connected to the circulation in order to be 

 easily brought to the required pressure. In the case considered here the 

 experiments were not made in the cryogenic laboratory but in an 

 other room and the length of the lead a\^ was 10 m. Although 

 the liquid ethylene had to be conducted over such a distance, yet 



