30 CAPILLARITY. LECT II. 



to the examination of the purely physical phenomena of 

 capillarity and imbibition; in order that, by means of the 

 information thus communicated, you may be enabled to 

 judge what part they play in the functions of absorption and 

 exhalation. 



Capillarity. As I purpose to confine myself to a simple 

 detail of facts, I shall here state, in the form of propositions, 

 the principal results, drawn from observations, of the phe- 

 nomena of capillarity. 



1st. When a body is plunged into a liquid, the latter is 

 either elevated or depressed around the solid, and presents, 

 at its point of contact with it, a concave or a convex surface, 

 according as it is either elevated or depressed. In the first 

 case, the immersed body is said to be wetted or moistened, 

 as when glass is introduced into water ; in the second case, 

 of which the immersion of glass in mercury is an example, 

 the solid does not become moistened. 



2dly. When we plunge two bodies sufficiently near to 

 each other into a liquid, the latter is either elevated or 

 depressed between them, according as they are or are not 

 moistened by the liquid. It is requisite that the two bodies 

 should be so near to each other that the two curved surfaces 

 formed by the liquid may touch. The elevation or depres- 

 sion of the liquid above or below its level, is in the inverse 

 ratio of the distance of the two bodies from each other. 



3dly. If we plunge, into a liquid, a glass tube open at 

 both extremities, the liquid rises or falls in the tube, and the 

 effect is greater in proportion to the smallness of the bore 

 of the tube. If we compare the elevation or depression 

 which takes place in a cylindrical tube, with that which is 

 observed between two glass plates separated from each 

 other by an interval equal to the internal diameter of the 

 tube, it will be found that the elevation or depression in the 

 tube is twice as great as that between the glass plates. The 



