WATER RAM

An ingenious hydraulic machine for raising water by means of its own impulse. The principle of its action and the mechanism of its construction may be described as follows: — The water arriving at A from the reservoir with the velocity due to the height of the fall pa es along the pipe A B, which should have an inclination of at least an inch for every two yards, escapes through an orifice C, which may be shut at pleasure by means of a valve. A reservoir, F, filled with air is attached by means of a cylinder, abed, to the pipe A B D; in the middle of the bottom of the reservoir F is a circular orifice, to which there is adapted a short cylindrical tube, of which the extremity E is also furnished with a valve. Another valve S serves to supply the air to the space comprised between the cylinder abed and the tube E. G I H is an ascensional tube rising from the reservoir F. The water which escapes at C is carried off by the waste pipe K L. The form of this apparatus (or perhaps its mode of action) suggested the name it has received. The pipe A B C is called the body of the ram; and the extremity, where the valves and the reservoir F are placed, is called its head. Both valves D and E are formed of hollow balls supported on muzzles, and of such a thickne of metal that they weigh about twice as much as the quantity of water they displace. We may now consider the effects of the engine when in action. The water flowing through the orifice C acqinres the velocity due to the height of the fall, and ra's es the ball D from its support till it comes to the orifice C; the extremity of this orifice is covered with leather, or with cloth filled with pitch, so that when the ball is applied to it the pa age of the water is effectually prevented. As soon as this orifice is closed, the water raises the ball E which had shut the orifice of the reservoir F; and a portion of it introduces itself into this reservoir, and into the pipe G I H. It thus loses the velocity which it had when the orifice C was shut, and the balls D and E fall down in consequence, the one on its support, and the other on the orifice at E. When this takes place, every thing is in the same state in which it was at first. The water begins again to flow through the orifice C; the valve D is again shut; and the same effects are re peated in an interval of time, which, for the same ram, undergoes little variation. Every time the impulse is renewed a quantity of water is forced up into the reservoir F and the tube H; and as it is prevented from returning by the miction of the valve, it must nece arily be delivered at the extremity of H. The use of the air-ve el F is to keep up a continuous motion of the ascending column of water. The communication with the external atmosphere being cut oflf, the air within F is compre ed by a force proportional to the height of the surface of the water in H above its surface in F; and this compre ed air acting by its elasticity on the water, maintains a continuous flow through H. The air-ve el, however, though it a ists the action of the ram is not an e ential part of it; the continuity of the discharge of water maybe effected by means of two or more rams, of which the ascensional pipes G I H all terminate in a single branch. On this principle works have been erected at Marly, in France, which raise water in a continuous jet to the height of 57 metres, or 187 English feet. Ae the ascending column of water communicates with the air in the reservoir F, this would soon be exhausted if a fresh portion of air were not introduced at each stroke of the ram. The little tube S, which is £topt by a valve opening inwards, serves for this purpose. At the instant when the orifice C is closed a recoil takes place, by which the water is thrown back from the head of the ram towards the cistern; and a partial vacuum being thus produced within the cylinder abed, the pre ure of the 570 A (1.) 3 a K =-^--^-— 11 -^^ g HYDRAULICS. external atmosphere forces open the valve in the canal S, and a portion of air enters the cylinder, whence it is driven into the reservoir, excepting the small part of it which lodges in the space between the cylinder abed and the tube E. (Hachette, Traite des Machines.) The invention of the hydraulic ram, at least in the improved form here described, belongs to Montgolfier of MontpeUer. A machine, however, on the same principle had previously been suggested.and even erected at Chester, by our countryman Mr. White hurst, but much le perfect in its mode of action; for the orifice C, instead of being opened and shut by the action of the water itself, required to be opened and shut by the hand by means of a stop cock. Owing to this circumstance, White hurst's machine was of little utility, and appears to have soon been entirely forgotten. HYDRAULICS (Yunanca köken — orijinale bakınız.), is that branch of natural philosophy which treats of the motions of liquids, the laws by which they are regulated, and the effects which they produce. By some authors the term Hydrodynamies is usually applied to the general science of the motions of fluids; while Hydraulics is more particularly applied to the art of conducting, raising, and confining water, and to the construction and performance of water-works. There is no part of mechanical science which offers greater difficulties to the mathematician, or where the results of theoretical investigation present so little agreement with experience. This arises from the exce ively complicated nature of the movements which take place among the particles of a liquid ma when its equilibrium has been disturbed, and partly from the great] number of disturbing causes by which those movements are affected. The first and principal problem of hydraulics is to determine the velocity with which a liquid flows througli an aperture in the bottom or sides of the containing ve el. In order to discover the law of this velocity, let A B C D (fig. 1.) be a ve el filled with water to the height E F, and let O be a very small opening in the side of the ve el; •while the water stands at E F it will i ue from O with a certain velocity depending on the height E F above O. Let it therefore be proposed to determine to what heiglit, G H, the ve el must be filled in order that the velocity of the efflux through O may be doubled. From the principles of hydrostatics it is shown that the force urging a particle of the liquid at O through the orifice is the pre ure due to the height of the vertical column above O. Now we may consider, in the first place, that when the velocity of a particle in motion is doubled, the momentum, or moving force, must also be doubled; and, in the second place, that if the velocity of the efflux is doubled, twice the number of particles will be put in motion in the same interval of time; and consequently the momentum or moving force must be doubled on this account also. Hence when the velocity of the discharge through O is doubled, the moving force, which in the present case is the pre ure, must be quadrupled. But the pre ure is proportional to the height of the fluid above O, hence the height must be quadrupled. By the same proce of reasoning we conclude that to obtain a threefold velocity a ninefold depth would be nece ary, and so on; ana, generally, that the depths must be increased as rapidly as the squares of the velocities; or, in other words, the velocities are proportional to the square roots of the depths of the orifice below the surface. By means of this law the absolute velocity with which water i ues from an orifice at any depth under the surface may be ascertained, provided we can determine the velo^ city for any particular depth. Now if we suppose the orifice O to be on a level with the surface of the liquid, or if we suppose O to be in the bottom of the ve el covered with an infinitely thin film, there would be no pre ure on a particle at O, which, therefore, would drop out merely by the efiect of its own weight, and consequently with the velocity of a heavy body beginning to fall. But the velocity of a falling body is proportional to the square root of the height from which it has fallen: therefore, since it has been shown that the velocity of the discharge through an orifice is also proportional to the square root of the height of the liquid above the orifice, and that the two velocities are the same in one particular case, it follows that they must be the same in all cases; and hence we have this important theorem:— "The velocity with which a liquid i ues from an infinitely small orifice in the bottom or side of a ve el that is kept full, is equal to that which a heavy body would acquire by falling from the level of the surYace to the level of the orifice." Several consequences follow immediately from this fundamental theorem. In the first place, if the aperture is enlarged, each particle of the liquid presenting itself there will escape with the same celerity; and hence the quantity of water that i ues through an orifice is as the area or section of the orifice multiplied into the square root of the depth. Again, if the water is thrown up in a perpen  [s. 583]