o5Ó 



kepeatetl lueasureiueiils «liow, tluü tlie accuracy of tlie reading ot' 

 tlie rise may be estimated at 0.002. 



The observed heights (A) have to be corrected for the curvature 



of the surfaces by means of the following formulae : (1) the correction 



r 

 for the meniscus in the narrow tube is - '). (2) the correction for 



the ring-shaped meni.scus is (according to Verschafffj-t (Jomm. N*. 18). 



2d 



h' 



r 



{R-r,y 



1 



2d 



r {R-r,y 



For this correction the height of the ring-shaped meniscus, as the 

 minor axis of the elliptical section with a meridian plane, is required 

 to be known. With the illumination used this height could not be 

 measured accurately. Afteiwards for fuither correction we hope to 

 be able to determine its value by special measurements: in the 

 mean time the section was assumed to be circular with sufficient 

 approximation. The corrected values are given in column 6 of table II. 



When the capillary rise is plotted as a function of the temperature 

 — fig. 2 — , a straight line is obtained. The constants determined 

 from this line give the formula 



11= - 0.1124 r 4- 40.44. 



This formula gives H=0 for r//=.orxfrup.= 35.98 K. 



Assuming the critical temperature to be 7\. = 31.1 IK (mean of 



I) Laplace, Mée. Cél. Tome X, Supp. § 5, Paris 1805. 

 id. , Oeuvres Tome IV, p. 415, Paris 1?^45. 

 Allan Ferguson, Phil. Mag., p. 128, (6j 28, 1914. 



