214 Mr POWER'S THEORY OF >! 



Let us now estimate all the forces which tend to move the central 

 column DyD^D-iDi in direction of its axis. 



It is plain that, in whatever manner the fluids may communicate 

 in the interior of the tube, the tube can produce no effect upon 

 ByBiBiBi, since every elementary portion of this part of the fluid 

 will be drawn in both directions as by an infinitely extended tube. 



We may also neglect, as producing equal and opposite forces in 

 both directions, the attraction between the tube A^B^ and the fluid 

 AiAiBiBi; between the tube A^Bi, and the fluid A^AzBiB,; be- 

 tween the fluid tube dA^Di, and AiA^D^D^ ; between C2A2D,, and 

 AzAzDiDs, between the membrane and C^A^D^-, between the mem- 

 brane and CiA-iD-i. 



Lastly, we may neglect all the mutual actions of the particles 

 composing the central column DyD^DiDi, their tendency being only 

 to mix the opposite fluids, and not to move the column as a 

 mass. 



Of the remaining attractions we shall have at one end the 



attraction of the tube B^Bt, upon B-^B^A^A^, ( = \ cH) + the 



attraction of the tube A^B^, upon D^D^A^A^, {= ^ cH) — the 



attraction of the fluid tube C^A^D^, upon A^A^B^B^, {=\cM); 



c 

 constituting the capillary force - {2H — M). This will be opposed 



by a similar force — {^K—N) exerted at the other end of the tube. 

 The residual sustaining force is therefore 



I .{2H-2K-M+N'). 



It now only remains to express this force in terms of the actual 

 densities r and p, and the initial constants 



{r), ip), {H), (K), (L), {M), {N). 



