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The Surface-Tension proves the existence of Cohesion. 
To prove this requires no molecular hypothesis, but before 
proceeding it may be well to define clearly the term cohesion. 
Cohesion in a liquid is here to be understood as a 
property which enables the fluid to resist any tendency to 
cause internal separation of its parts — any tendency to draw 
it asunder, or more definitely, it is the property which 
enables a liquid to resist a tension or negative pressure. 
Let us suppose a mass of liquid without internal cohesion. 
Then any external action tending to enlarge the capacity 
within the bounding surface of the liquid would at once 
cause the interior of the liquid to open, and a hollow would 
be formed within the liquid without any resistance on the 
part of the liquid. Such a condition is inconsistent with 
surface-tension, for the tension of the surface of the internal 
hollow would tend to contract the hollow ; and since the 
interior of the hollow is supposed to be empty, there could 
be no resistance to the tendency of the surface to contract 
such as that offered by the pressure of the gas within an 
ordinary bubble. Hence any force that might, under the 
circumstances, balance the surface tension and keep open 
the hollow, must be supplied by the suction or cohesion of 
the liquid outside. — Q.E.H. 
Again; the intensity of cohesion is determined by the 
intensity of the surface-tension, and the smallness of the 
least possible opening over the surface of which tension 
exists. 
In so far as has yet been determined by experiment, it 
has been found that the surface-tension is independent of 
the curvature of the surface — is constant for the same liquid. 
Assuming that this is the case it follows, that the intensity 
of the force necessary to keep a spherical bubble or opening 
from contracting (whether this force arises from the pressure 
of the gas within the bubble or the cohesive traction of the 
liquid without the opening) is equal to twice the intensity 
