188 OUTLINES OF NATURAL PHILOSOPHY. 



278. If into a conical capillary tube, held in a 

 horizontal position, a drop of water be introduced, 

 it will run toward the narrow end ; but if a drop 

 of mercury be introduced, it will run toward the 

 wide end. . 



LA PLACE, Mecanique Celeste, Lib. x. Supplement, 

 p. 6. 



279. Whether a fluid rise or fall between two 

 vertical and parallel planes of glass, immersed in 

 the fluid at their lower extremities, the planes tend 

 to approach one another. 



a. It is from this tendency, that two small vessels of 

 glass, of a parallelepiped form, floating on water or 

 mercury, unite, whenever they approach near to one 

 another. LA PLACE, ibid. 11. 



b. The phenomena here enumerated, clearly prove the 

 existence of an attractive force between water and 

 glass, but require to be carefully compared before 

 they inform us of the manner in which that force 

 is exerted. The fact that points most directly to 

 the place where the force resides, is that of the 

 concavity of the surface, mentioned at 273. 



280. From this fact it may be inferred, that a 

 narrow ring or zone of glass immediately above 

 the surface of the water, attracts the water with a 

 force which, when the tube is of a small diame- 

 ter, is able to suspend a thin film of the fluid in 



opposition 



