$gg OS CAPILLARY ACT10W. 



for the fluid contained in this first branch. Let us analyse 

 these different attractions with care, and first consider those 

 that take place toward the lower part of the first tube. 



Attractions to- For this let us conceive, that the base of the tube is ho. 



tomVflhcmbe- rizontaI - The fluid contained in the second tube will be 



attracted vertically toward the bottom, 1st by itself, 2dly, 



by the fluid surrounding the second tube. But these two 



attractions are destroyed by the similar attractions, that the 



fluid contained in the second vertical branch of the canal ex. 



periences near the surface of the level of the fluid. Ac* 



cordingly we may leave them out of consideration here. — 



The fluid in the first vertical branch of the second tube will 



also be attracted perpendicularly upward by the fluid in the 



first tube. But this attraction will be destroyed by the at. 



traction it oxerts on the latter fluid : these two reciprocal 



attractions therefore may be set aside. Lastly, the fluid in 



the second tube will be attracted perpendicularly upward 



by the first tube, and hence this fluid will have a vertical 



force, which we shall denote by Q, that will contribute to 



destroy the excess of pressure owing to the elevation of the 



fluid in the first tube. 



Forces acting j^t us now examine the forces, with which the fluid in 



on the fluid in , „ , . T . , , . , 



the tube. the first tube is actuated. In its lower part it experiences 



the following attractions : 1st, it is attracted by itself ; but 

 the reciprocal attractions of the particles of a body impress 

 upon it no motion, if it be solid; and we may conceive the 

 fluid in the first tube to be consolidated, without any dis- 

 turbance of equilibrium. 2dly, This fluid is attracted by 

 the fluid in the interior of the second tube : but we have seen, 

 that the reciprocal attractions of these two fluids destroy 

 each other, and must not be taken into account. 3dly, It 

 is attracted by the exterior fluid, that surrounds the second 

 tube ; and from this attraction results a vertical force acting 

 downward, which we shall denote by — Q'. We prefix to 

 this the sign — , to indicate, that its direction is contrary to 

 that of the force Q. We shall observe here, that, if the 

 laws of attraction relative to the distance be the same for 

 the molecules of the first tube and those of the fluid, so that 

 they differ only in respect to intensity ; if we nominate these 

 intensities in equal volumes £ and ^', the forces Q and Q are 

 3 proportional 



