( 292 ) 



as the refasteiiiiig in llie cryoslal would have imohed iiiaiiy (liffu-uU 

 operations. 



Therefore in oider to bring t lie resistance thermometer to a constant 

 temperatn]-e near (f C, the case U of the cryostat (PI. I, Conim. 

 N". 83) was screwed off from tiic cover A", (PI. I, Comm. N". 5J), 

 whih' the other parts of the cryostat remained fastened to the cover, 

 and it was rephiced hy a zinc cylindrical vessel, which could be managed 

 more easily. This \ esse! was provided with a rim tilting on to .V^ 

 and was placed in another larger zinc \essel, so that a Jacketing 

 space of 5 cm. remained which was entirely fdled with ice. Then 

 isopentane \vas distilled into />\,, (PL II, Comm. N". 83) and the 

 apparatus was left to itself during one night. The next day the 

 temperature (near 0°) had become constant and we determined it 

 (while stirring) by nieajis of a thermoelement {& PI. II, Comm. N". 83). 



§ 7. Corrertioiis. X survey of the mounting of the Whkatstone's 

 bridge (cf. § 3 Comm. N". 77) is given in tig. 5. li indicates the 



rig. 5. 



i-esistance to be measured, A\ and II, the two coils of manganin 

 wire, E^ and E^' the resistance l)oxes of Hart.mann and Braun and 



of Siemens and Halske nivinu' together the resistance E.j^^=:ii^ 



e:^r," 



which with r.,^ forms the fonrth ai-m of the bridge; C\ and ('.^ are 



the commutators with niercnry contact (Comm. N". 27, May and June 



1896), C\ is the copper commidator treated in § 3 Conini. N". 77 and 



represented tliere in tig. 2. 



Putting for the factor for the inequality of the bi-anches of the 

 j> 



1 — a, we found a = 0.00216 (as mean \alue of twejity 



bridge 



E. 



