510 



§ 1 and of the well-known behaviour of liquid mercury, we calculated 



in each case the ratio — . 



As in these experiments the mercury resistance was suspended in 

 a vacuum-vessel cooled from the outside, the freezing took place 

 very slowly. 

 We found: 



23 May 1911 4.40 

 30 „ „ 4.63 



27 Oct. „ 4.41 



4.84 

 12 Jan. 1912 4.30 w,o 



3.06 W[3o 

 17 Febr. „ 4.69 



4.19 

 22 „ „ 4.30 



14 .luue „ 4.37 



4.90 

 As probably the highest figure thus obtained comes nearest to 

 the true value of the ratio, we will be not tar from the truth, if 

 we assume the number 5 for the mean ratio. 



This result has also been found by Baltkuszajtis '), wiio obtained 

 4.90 as highest value in his melting-experiments. 



It is remarkable, that the ratio of the change wi(h temperature 

 of solid and liquid mercury is also about 5 ; the increase of resistance 

 per degree lemains thus fairly constant in melting. 



^ 4. Some determinations of the chawje la resistance idtk the 

 temperature of metals and alloys. 



a. Object of the e.vperlments. We made a series of determinations, 

 mainly for orientation, about the change of resistance of different metal 

 wires down to helium-temperatures. The purpose of those determinations 

 was to find a metal or an alloy, which could be used as a resistance 

 thermometer down to the lowest helium temperatures. The results 

 of these measurements are plotted in figure 2. Of special interest is 

 the behaviour of manganin and constantin. While with copper, tin, 

 iron and cadmium no further change of resistance could be established 

 in the region of the lowest temperatures, it appeared, that the resistance 

 of manganin diminished considerably and in a lineai' way with the 

 temperature, from the lowest oxygen temperatures down to the region 

 of the helium temj)eratures. So that wires of manganin might be 



1) A. BalikuöZAjxiö, Cracoviu Bull. Acad. Nov. 1912. 



