ON SIPHONS AND JETS OF WATER, 403 



vibrations of pendulums; thus, if a long tube be immersed in a 

 fluid, in a vertical direction, and the surface of the fluid within the 

 tube be elevated a very little, by some external cause, the whole 

 contents of the fluid will be urged downwards by a force, which 

 decreases in proportion to the elevation of the surface above the 

 general level of the vessel, and when both surfaces have acquired 

 the same level, the motion will be continued by the inertia of the 

 particles of the fluid, until it be destroyed by the difference of 

 pressures, which now tends to retard it ; and this alternation will 

 continue, until the motion be destroyed by friction and by other 

 resistances. It is also obvious, that since any two vibrations, in 

 which the forces are proportional to the spaces to be described, are 

 performed in equal times, these alternations will require exactly the 

 same time for their completion, as the vibrations of a pendulum, 

 of which the length is equal to that of the whole tube ; for the 

 relative force in the tube is to the whole force of gravity as the 

 elevation or depression is to the whole length of the tube. Hence 

 it follows, that if two such tubes were united below, so as to form 

 a single bent tube, the vibrations might take place in the whole 

 compound tube, in the same manner, and in the same time, as in 

 each of the separate tubes; nor would the effects be materially 

 altered if any part of the middle of the tube were in a horizontal 

 or in an oblique direction, provided that the whole length remained 

 unaltered. In such a tube al&o, all vibrations, even if of consider- 

 able exteut, would be performed in the same time, and would long 

 remain nearly of the same magnitude; but in a single tube, open 

 below, the vibrations would continually become less extensive, and 

 their duration would also be altered as well as their extent; besides 

 the unavoidable resistances, which would in both cases interfere 

 with the regularity of the effects. 



Mr. Whitehurst, in the Philosophical Transactions for 17/5, has 

 given a curious account of the application of these principles in a 

 contrivance for raising water, employed at Oulton, Cheshire, the 

 seat of Philip Egerton, Esq. The water was contained in a reser- 

 voir, from the bottom of which there passed a pipe to the kitchen, 

 sixteen feet btlow the reservoir. This pipe had two extremities; 

 one of them furnished with a stop-cock, was for the use of the 

 kitchen; the other furnished wilh a valve, terminated near the 

 bottom of a stout vessel containing air. From the bottom of this 



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