HYDRAULICS 



course of the fluid, such as appears at B : 

 yet the course may descend to any depth, 

 as at C, provided the pipe be brought 

 back to the original height. If either end 

 be in the smallest degree lower than the 

 other, the water will sink to the level of 

 the lower retaining brim. And if the sup- 

 ply be continual, the water issuing from 

 the lowest end will mount nearly to the 

 level of the source. This is the principle 

 on which fountains are in general found. 

 To effect this, however, the pipe should 

 be small, so as to contract the issue of the 

 fluid, and to give it greater velocity, by 

 causing it to expose a smaller surface for 

 the air to press upon. This contraction 

 should not be carried to excess; else the 

 water would want force to pass through 

 the atmosphere, and, being subdued, 

 would break into drops, and fall without 

 gaining any height. The conduit-pipe is 

 usually made about five diameters of the 

 fountain-pipe ; under such proportions 

 the water will ordinarily flow so freely as 

 to give a good jet. 



The inelastic nature of water causes it 

 to retain its surface perfectly level; were 

 it otherwise, vessels would often run 

 aground, where, at present, they find 

 depth sufficient to float them ; and the 

 whole body of a river would present a 

 thousand opposing and unequal resistan- 

 ces ; whereas we find the resistance to be 

 uniform. To prove this, let a piece of 

 wood be put into a pail of water, the 

 fluid will in every' part remain equally 

 dense, and the surface will be perfectly 

 level. For a further elucidation of 

 this property, we refer to HYDROSTATICS, 

 wherein it will be found very conspicu- 

 ous. 



The ingenious Mr. Bramah has lately 

 applied the inelasticity of water to a va- 

 riety of purposes, especially in the ap- 

 plication of a power to remote effects. 

 Thus, if water be filled into the pipe, A B 

 C D, fig. 3, and that a piston be applied 

 to A B, made perfectly tight, so that no 

 water can possibly escape, when that pis- 

 ton is pressed down by means of a force 

 capable of overcoming the friction of its 

 sides, and the friction of the water within 

 the tube, it will cause the water to rise in 

 the pipe, C D, whatever may be the 

 length of the conjunctive part, A C. 

 Therefore, if a piston is inserted into the 

 pipe C D, it will be acted upon in perfect 

 conformity with the motion of the piston 

 in A B ; the power to move which may 

 be trifling, when the diameter of the pipe 

 is small, and the purpose not relating to 

 forcible operations^ Thus, for the mere 



intention of ringing a bell at D, a hundred 

 yards distant from the pwll, A, a bore of 

 less than a quarter of an inch in diameter 

 would answer every purpose, and would 

 yield to the pressure of the finger, with 

 very little exertion. On the other hand, 

 when machinery is to be set in motion, 

 the size of the piston, and the force 

 whereby it is to be moved, must be pro- 

 portioned to the resistance generated by 

 friction, and by the opposition to the ac- 

 tion of the machine. It is necessary to ob- 

 servej that where the two pistons are of 

 equal diameter, their actions will be 

 equal ; but that if the pipe, A B, be larg- 

 er than C D, it will produce an increased 

 action in the latter, which, in such case, 

 must have a proportionate increase of al- 

 titude, and, vice versa, when the action of 

 A B is to be greater than that of C D. 

 Our readers will be sensible that a tube of 

 less diameter can be made to contain the 

 same quantity as that of greater capacity, 

 only by adding to its length ; and that 

 both their areas being filled and emptied 

 alternately by the same action, and in the 

 same time, that which has the greatest al- 

 titude must have the greatest scope of 

 action, and move with an increased velo- 

 city in exact ratio with the difference of 

 the diameters. When the velocity of the 

 machinery attached to the movement- 

 tube is to be diminished, without losing 

 the height to which the secondary power 

 is thus raised by the Additional length of 

 the tube, the segment on which it is 

 made to act must be that of a larger cir- 

 cle, as shewn in fig. 4, where the tube, 

 A B, is of double the diameter of that at 

 C D, which would raise the lever, E, to 

 the height F. Now, if this lever were the 

 handle of a pump, requiring a considera- 

 ble exercise of power, it is evident the 

 fulcrum,G, mustbe placed very nearto the 

 pump- tube, H ; whereby the radius of the 

 circle, G F, is greatly increased, and the 

 plonge of the pump-piston, H, much di- 

 minished. If, on the contrary, the fulcrum 

 had been at O, i. e. dividing the distance 

 between D and X into three parts, of 

 which two are given to the lever, N, the 

 plonge would be far deeper, but the 

 power would be greatly reduced; the 

 segment,|D F, occupying a greater angle 

 with the fulcrum O, than it does with the 

 fulcrum G. This is amply explained un- 

 der the head of MECHANICS. 



Where water is enclosed within a ves- 

 sel, or in a tube, in such manner that air 

 cannot penetrate, it will not flow out in 

 the same manner, as if air were admitted 

 to supply the place of any quantity that 



