﻿248 M. G. Quincke on the Capillary Phenomena 



A numerical value for the magnitude « 12 , the surface-tension 

 of the common surface of two liquids, is, to my knowledge, no- 

 where given. 



3. If we denote by z the vertical distance of a point P 12 , of the 

 common surface of two liquids of specific gravity <t x and<r 2 , from 

 the horizontal part of the common surface of the liquids, and let 

 the positive axis of z coincide with the direction of gravity, then 

 from equation (1), and the hydrostatical proposition that in a hori- 

 zontal plane in the interior of the same liquid there must every- 

 where be the same pressure, the equation follows, 



fo-*>=«]«(]j +-g?) ( 3 ) 



This equation would relate, for example, to the case where a 

 spread drop of mercury in water is poured on a horizontal base. 

 If the diameter of this drop is large, or if it be poured into a tray- 

 shaped channel, then B/ is very large, ^ to be neglected as com- 



1 . 



pared with ^-, and equation (3) becomes 



fz_ 



■ ± « lg 1 _gf 2 dx* 



■•■-* "•['+©?• ■' 



in which the specific cohesion of the common surface of the 



liquids, 2u 



2 



(5) 



is introduced instead of the capillary-constant or surface-ten- 

 sion « 12 . 



The integration of equation (4) gives 



z* ' I 1 



= const. i— T^tffr 



fll2 



"vMS 



(6) 



Ji 



-^- = 1- COS 12 , 

 "12 



in which o 12 is the angle which the element of the curve of the 

 meridional section of the surface makes with the horizontal x axis. 

 For the horizontal upper surface of the drop, z and o 12 simul- 

 taneously equal zero. 



For a vertical element of the curve of the meridional section 



z—Zi ]2 =9O , 



