294 Hydraulics for Farmers. [June, 



machine for raising water by its own impulse, and comes nearer 

 to a perpetual motion than any other machine that has ever fallen 

 under my notice. 



If a column or body of water, moving rapidly under a head, 

 through a pipe, is suddenly checked, its tendency is to burst the 

 pipe. This is well known in all places where there are water- 

 works, from the bursting- of the leaden supply-pipes, where these 

 are not strong enough, on the sudden shutting off the hydrant 

 cocks. If a small hole is made in the pipe, just above the cock, 

 the water will escape from it in a very high jet, much higher 

 than the head, whenever the cock is shut. It is this principle 

 which is brought into action in the hydraulic ram. If a small 

 straight upright pipe is attached to the hole, just mentioned, in 

 the main pipe, having a valve shutting downwards, which will 

 permit the water to pass upwards, but not to return, each opening 

 and shutting of the cock will force up into the smaller pipe a 

 quantity of water in proportion to the head upon the main pipe, 

 until the weight of the water in the smaller pipe is greater than 

 can be moved by the momentum of the water in the main pipe, 

 when the latter is suddenly closed. 



Every person accustomed to draw water from pipes that are 

 supplied from very elevated sources, must have observed, when 

 suddenly closed, a jar or tremor communicated to the pipes, and a 

 snapping sound, like that from small blows of a hammer. These 

 effects are produced by blows which the ends of the pipes receive 

 from the water — the liquid particles in contact with the plug of 

 a cock, when it is turned to stop the discharge, being forcibly 

 driven up against it by those constituting the moving mass be- 

 hind. 



Waves of the sea act as water-rams against rocks or other bar- 

 riers that impede their progress; and when their force is increased 

 by storms of wind, the most solid structures give way before 

 them. 



The increased force water acquires when its motion is accele- 

 rated, might be shown by a thousand examples. A bank or 

 trough that easily retains it when at rest, or when slightly moved, 

 is often insufficient when its velocity is greatly increased. When 

 a deep lock of a canal is opened to transfer a boat or vessel to a 

 lower level, the water is permitted to descend by slow degrees. 

 Were the gates opened at once, the rushing mass would sweep 

 the gates before it, or the greater portion would be carried in the 

 surge quite over them, and perhaps the vessel also. A sluggish 

 stream drops almost perpendicularly over a precipice; but the 

 momentum of a rapid one shoots it over, and leaves a wide space 

 between. It is so with a stream issuing from a horizontal tube. 

 If the liquid pass slowly through, it falls inertly at the orifice; 



