( 643 ) 



Constantiii and stoel appeared to satisfy the recpiii'eiuejils ioi- tlienno- 

 elements laid down in ('onnn. N". 27. We snceeeded in findina' 

 wires of which, after tiiey iiad been treated as described in Comni. 

 N". 27, the potent ial-diHerences at a teniperatnre (htierence of 100° (^ 

 amount to no more than 0.5 mici'ox'olt ah)nL^- tiie whole wire and at 

 the extremities over a length from 50 to (iO cm. no moi-e tiian 

 0.05 microvolt ^). 



In order to be al)le to test whether the element is free of current 

 a steel wir(^ has been sohlercMl on to each of the ends of tiie wire. 

 The junctures of the two steel wires with tlie copj)ei' leads are kept 

 at an ecpial constant lemperatnre viz. O'' ('. Eacli of tliese |)j-otected 

 junctures constantly kept at O"" C has its own ice-pot which is mounted 

 insulated iVom the others (See tig. J PI. I and compare with this 

 ligs. 1 and 2 of PI. 1 (\»mm. N". 27). 



As to the j»rinci[)al features the arrangement of the lindts like 

 that of the vvliole element has remained the same as in Comm. N". 27. 

 The constantin wire, wiiich like the German-silver wire might easily 

 be l)ent in shai'p cur\es and then siiow disturbing electromotive forces, 

 is again })rotected by a thicdcwalled indiarubber tube comiected 

 hermetically with the glass pr()lecting-tvd)es of the limbs. Owing to 

 its elasticity the steel wire did not reqnire this ])r()tection ; a layer 

 of shellac {)rotects it from rust (for a better protection of tiiis layer 

 it may also be coated with a thinvvalled indiarubber tnbe). 



In the limb constantin-steel the constantin-wire (1 mm. thick, 0.25 

 ii resistance ])er m.) is enclosed in the inner glass tube (see lig. 2 

 PI. 1 and comj). tig. 4 PI. Ill Comm. N". 27), the steel wire goes 

 straight between the inner and the outer tnbe (see tig. 2 PI. I and 

 comp. fig. 4 PI. Ill of (V)mnj. N". 27). Owing to the small conduc- 

 tivity it was not necessary to wi]]d the steel wire round the inner 

 tnbe (see \fig. 4 PI. Ill of Connn. N". 27). For the limbs which are 

 always immersed in ice, a iirm oidei- protecting-tube is very desirable 

 with a view to the circumstance that the ice must repeatedly be 

 [jacked together. Each ice-|)ot is eiiclosed in a protecting cone-shaped 

 piece of paste-boai'd soaketl in oil of which the lower i-iiri stands in 

 in the watei- on its dish, thus forming an air-jacket roinid the ice-pot 

 which is closed at the bottom; yet in warm weather it is advisable 

 to pack tlie ice every five minutes. 



Although to sim[)lify the constructio]) of the elements we have 



1) The detects which weie avoided in the Irealment described in Comm. iN". '■21, 

 have later been delected in thermoelements of tlie l/*liys. Tcchn. Reichsanslalt. 

 There tlie treatment consideied has also been applied in following cases. (Cf. 

 Zeilschr. f. Inslrk. Bd. 19. p. 249, 1899). 



