On the Maximum Tension of Vapours. 245 
is proportional to the tension w, of the vapour in contact with 
it, so that 
| NY =Kwu, . 
we have N’=Ko,=K.o, (1 os iy ee KC = ) 
so that if the tension near the bent surface becomes » the number 
‘ : 5 a teak 
entering from it becomes Ko=K,o(1 - a) 
This must be equal to N when there is equilibrium, and N,= 
N,’ if w, be the tension corresponding to the flat surface, so that 
we get 
“(1-7 =#. (141) 
Hence, we see that the maximum tension near a curved sur- 
face exceeds that near a plane by a quantity which varies vn- 
versely as the radius of curvature of the surface: and this is the 
same law as Sir Wm. Thomson arrived at. 
In order to utilize this formula for measurements of surface 
tension it would be necessary to know something about the law 
of emission and rates of evaporation. It might be possible to de- 
termine something about the latter by observing under a micro- 
scope the rates of evaporation of drops of various sizes, and by 
that means estimating k, 
NCIEN EkOG., h.DS. VOL, i, Pt, 1: 
wm 
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