857 



b 



m ■= a '^ 



t 



where a is the unknown eorrertion and b a constant, which is equal 

 to the product of the corrected mass and the time. From a series 

 of measurements with different m the constants a and b may be 

 calculated. 



In order to avoid the use of different masses which involved 

 openino;, refilling and reclosing the tube, an attempt was made to 

 determine the correction in a different manner. By dividing a given 

 quantity of mercury into a train of drops which fall down together 

 the capillary action is multiplied ^). If the influence of each separate 

 drop is the same, the correction must be proportional to the number 

 of drops. Calling the number of drops x, Rankine's equation becomes 



b 



m znz xa A . 



t 



a and b may thus be calculated from several measurements with 

 different x, m being known. If ??i is taken as unknown, the ratios «/?« 

 and bim may be found. Calling these ratios a^ and b^ the equation 

 takes the form 



1 



a.x 4- 6, — = 1 

 t 



b^ is thus the time for .v = i.e. the time corrected for the 



influence of capillarity. According to this equation the graphical 



1 

 relation between a; and - should be a straight line. 



In the application of this method some unexpected difficulties made 

 their appearance. 



To begin witli the constants a and b were derived from three 

 observations by Rankine's method. 



Rankine's method m 1.86 1.31 1. 01 grms 



' . t 57.1 84.5 114.2 seconds, 



temp. 14.5°. 

 These results give : 



a = .160 6 = 97.10. 



The observations with air were now repeated by the drop-method. 



1) By providing the wide tube witli a small contraction on the inside of the 

 curve near one of the bulbs, it is easy to divide the mercury column into two 

 or more drops. 



