( 503 ) 



and 78, March '02) and the comparison Itetween the platinum resistance 

 lliornioiiu'lei- and tlic Iivdrouvii tlicrinoiiiclcr (Counii. 77 lu'hi'. '()2) in 

 this description, as i)i ('onnn.ol. Scpi. <»!», il seems to me desiralile to 

 illnslrate tlie use of the ci-voslal hy means of a special example. We 

 will consider the ('om|>aris()ji (if llic liydroj^eii lli(M-m(HMel(>i- with 

 llic resistance lliernidmetef where also a ihcnno-eienieni had Iteeii 

 immersed in ihe hath. 



Plate 1 shows the cryostat and some of the au\iliar\ ap|>aratiis 

 to scale, the coimections are i-epresenle<i sehematicalU-. It has heen 

 drawji on a small(>r scale than plate I of ('omin. 51 Sept. lÜI, f which 

 should he considted to^'ether with the one now giveji) hut il will sniïiee 

 to ^ive a survey of the whole arrangement and to show some 

 of the allei-ations. While the details of the luimodilied parts can l)(> 

 studied on plate 1 of ('omiu. 51 , |)hile 1 1 of the present (Communication 

 shows the details of the parts enclosed hy the dot-dash-line of plate 1, 

 as far as they aiv r<'(|uired foi- consideration of the new arranjiements. 

 The connection of the apparatus shown in PI. 1 with the <ias circu- 

 lation can he seeji in Pi. IV (V)mm. 51. The comparison of the 

 platinum thermomeler ji and the hydrogen thermometer 77/ and their 

 coimections to the other pieces of the ai)paratus are given in ('omm. 77 

 Fehr. 'O'l §8. For the comparison (tf Ihe thermo-element (•) \ am as 

 yet ohliued to i-efer to the \ery rouuh diagram of 189H (PI. 1 of 

 (Vunm. 27 Mai and .lime 'DO). The conniiunicatioii. howcNcr. of some 

 i-esidts f(M- which Ihe lemperalui-es have heen delermined hy juean> 

 of a thermo-element will soon call for a description of the i-ecent 

 considerahle improvements in the use of the tlieruio-elenients. 



On |>lates 1 and II a cori-ection ihei-niometer C. Avliich is enlirelv 

 independent of the cryostat, w ill he seen besides the thi'ee measuriuu' 

 apparatus mentioned ahoNc. It serves in oui" case to indicate the 

 mean temperature of the capillary of tli(> hydrogen Ihermomeler, (u- 

 in genei-al, the mean temperature of similar jiieces of measuring 

 apparatus occupying tli<> same part of the cryostat. For this 

 purpose two spirals of |»latinum wire are wound round a glass rod, 

 the one for thai |>art of the rod, where the lem[)erature varies slowly C,, 

 the other hn- Ihal part where the lemj)eratnre varies rapidly C,. \\\ 

 means of the leads C„„, connected to the plai-es of contact il,,,C,jand 

 ^.ji and emerging through the lid)e s,,,. we can determine the resis- 

 tance ot" these spirals. 



§ 2. First we shall mention some small changes in Ihe crvoslal 

 of ('omm. 51 which have no relatioji to the (|uestioji of keeping 

 the temperature constant and uniform. 



