6 JOHN JOHNSTON AND L. H. ADAMS 



A slight modification of this formula is directly applicable to 

 the capillary rise of Hquids in fine tubes. Consider a tube, open 

 at both ends, partly immersed in a vessel of liquid, which will rise 

 in the tube to a certain height h (Fig. 3). When the rise is several 



Fig. 3. — Diagram 



times the diameter of the tube, the curvature of the free surface 

 in the tube is sensibly uniform; in other words, the surface is a 

 segment of a sphere whose radius is p. Now, according to 

 equation 2, the pressure on the under side of the curved surface 



