Floating Bodies and the Theory of Capiliarity. 311 
w = weight of unit-volume of liquid, for tubes, 
and w= weight of unit-volume of liquid, for parallel 
plates. 
hk =mean height of meniscus above level, for tubes, 
and A’= mean height of meniscus above level, for 
parallel plates. 
Then for cylindrical tubes, the whole force exerted at the 
Margin of the surface of the liquid in the interior =zdxT; and 
is vertical component = zdxTxXcos a. This latter must be in 
equilibrium with the weight of the column of liquid elevated 
or depressed above or below the hydrostatic level. This weight 
ye x wxh. Hence, equating this force with the vertical com- 
ponent of the tension, we have “d*xwxh = 2dX TX 008 a. *." 
4T x cos a ; 
= 5p i ; which gives Jurin’s law of inverse diameters. 
_  &Xw 2T’ a et 
Similarly, for Parallel Plates, we have, h’= x. And, 
€ must have T = it follows from the above, that when 
d=d’, h! = z=. 
as according to the Reger for any given liquid and solid, 
WwW ve . : 
From the foregoing equations, expressions for the values of 
T and T’ can be readily deduced: Thus, we have, 
hxdxXw ,_Wxdxw 
te 4c0s @ » and T= 2cos a ~ 
In the case of water in a clean glass tube which has been 
Well wetted with that liquid, the angle a is very generally as- 
sumed to be zero, that is to say, the interior wall of the tube 
1s tangential to the marginal surface of the meniscus,—so that 
COs @ = 
for, in the case of all liquids which wet the surface of glass 
tubes, experiment shows, that the value of a depends upon 
temperature. It appears from the experiments of Briinner and 
of Wolf on the elevation of ether, bisulphide of carbon, oil of 
