. The physiology of domestic animals ... Physiology, Comparative; Veterinary physiology. FlG. 34. Fig. 36. Diagrams illustrating Cause of Curvature of Liquid Surfaces in Contact with Solids. (Ganot.) The molecule m ia acted on by gravit}', in the vertical line in P: is attracted by the plate n, in the line n m, and by the liquid F, in the line m F. The direction of the resultant m R will depend upon the relative intensities of these forces. If n in and in F balance, the resultant is vertical, //( R (Fig. 34), and the surface is horizontal. If it in increases, or in F decreases, the resultant R
. The physiology of domestic animals ... Physiology, Comparative; Veterinary physiology. FlG. 34. Fig. 36. Diagrams illustrating Cause of Curvature of Liquid Surfaces in Contact with Solids. (Ganot.) The molecule m ia acted on by gravit}', in the vertical line in P: is attracted by the plate n, in the line n m, and by the liquid F, in the line m F. The direction of the resultant m R will depend upon the relative intensities of these forces. If n in and in F balance, the resultant is vertical, //( R (Fig. 34), and the surface is horizontal. If it in increases, or in F decreases, the resultant R is within the angle n m P, and the surface is concave (Fig. 35). If in F increases, or n in decreases, the resultant R is within the angle P m F. and the surface is convex, for the surface of a liquid is always perpendicular to the resultant of forces acting on its molecules (Fig. 36). The ascent or descent of liquid within a capillary tube is dependent on the maimer in which the curvature of the surface modifies the prin- ciples of hydrostatic equilibrium. When a tube of large calibre is immersed in a vessel containing liquid the conditions of equilibrium are the same as in two communicating vessels containing the same fluid. Equilibrium is only possible when the surface of the liquid in both vessels is on the same horizontal plane. For, take any molecule -in the plane MN (Fig. 37). It will be subjected to a downward pres- sure equal to the weight of a column of the same fluid, the height of which is equal to the distance of that molecule from the surface of the fluid within the tube. It will also be subjected to an upward pres- sure which is equal to the weight of a column of liquid whose height is equal to the distance of that plane from the surface of the liquid without the tube. These weights arc, however, equal. Therefore every molecule in the plane MN will be subjected to equal and contrary pressures, and will consequently be in equilibrium. Suppose, however, the tube h
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