Capillary Attraction. 341 



allel to each other. The result of h- : s observations was as fol- Fifl224 

 lows. 



Distance of the plates. Height to the lowest point Temperature. 



of the concavity. 



1,069 13,574 62. 



458. Let AE be a vertical tube whose sides are perpendicular to Fig.222. 

 its base, and which is immersed in a fluid that rises in the inte- 

 rior of the tube above its natural level. A thin film of fluid is 

 first raised by the action of the sides of the tube ; this film raises 

 a second film, and this second a third, till the weight of the vol- 

 ume of fluid raised exactly balances all the forces by which it 

 is actuated. Hence it is obvious, that the elevation of the col- 

 umn is produced by the attraction of the tube for the fluid, 

 and the attraction of the fluid for itself. Let us suppose that the 

 inner surface of the tube AE is prolonged to , and after bend- 

 ing itself horizontally in the direction ED, that it assumes a 

 vertical direction DC; and let us suppose the sides of this tube 

 to be formed of a film of ice, or to be so extremely thin, as not 

 to have any action on the fluid which it contains, and not to pre- 

 vent the reciprocal action which takes place between the parti- 

 cles of the first tube AE and the particles of the fluid. Now, 

 since the fluid in the tubes JlE, CD, is in equilibrium, it is ob- 

 vious, that the excess of pressure of the fluid in AE is destroy- 

 ed by the vertical attraction of the tube and of the fluid upon 

 the fluid contained in AE. In analysing these different attrac- 

 tions, Laplace considers first those which take place under the 

 tubedB. The fluid column BE is attracted, 1. by itself; 2. 

 by the fluid surrounding the tube BE. But these two attrac- 

 tions are destroyed by the similar attraction experienced by the 

 fluid contained in the branch DC, so that they may be entirely 

 neglected. The fluid in BE is also attracted vertically upward 

 by the fluid in AE ; but this attraction is destroyed by the 

 attraction which the fluid in BE exerts in turn upon that 

 in AB, so that these balanced attractions may likewise be 

 neglected. The fluid in BE is likewise attracted vertically 

 upwards by the tube AB, with a force which we shall call ^, 

 and which contributes to destroy the excess of pressure exertecf 

 upon it by the column &F,raised in the tube above its natural level. 



