Proceedings of the Literary and Philosophical Society of Manchester Volume 16-19 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1877 Excerpt: ...the liquid is, I believe, possible; but this is beside my present purpose, which will be completely served by showing that 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.D. Again; the intensity of coliesion 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....