HYDRAULICS. 



lower end of the pipe q q, and is made to 

 open upwards into an air-vessel, hav- 

 ing a discharging pipe x ; and conse- 

 quently whenever the valve s is closed, 

 the water, which otherwise would have 

 flowed from the orifice r, now opens 

 the valve it and enters the air-vessel, 

 until the spring of the contained air 

 overcomes the gradually decreasing 

 force of the momentum, when the valve 

 u closes, and that at s opens to permit 

 the water to make a second blow or 

 pulsation, and in this way the action 

 of the machine continues unceasingly 

 without any external aid so long as it 

 is supplied with water and remains in 

 repair. A small running stream is 

 necessary for this machine, as the 

 water at'o should be kept at one con- 

 stant elevation to insure the perfection 

 of its action. A much greater quantity 

 of water likewise escapes at the orifice 

 r, between the pulsations, than can be 

 raised in the delivering pipe x, particu- 

 larly if it extends to any considerable 

 height, for the comparative quantity of 

 water discharged through x, and per- 

 mitted to run to waste at r, must al- 

 ways depend upon the respective per- 

 pendicular heights of the pressing 

 column o v, and the delivered or resist- 

 ing column u x, and the rapidity of the 

 pulsations will likewise depend on the 

 same circumstances. A very insignifi- 

 cant pressing column o v is capable of 

 raising a very high ascending column u 

 x, so that a sufficient fall of water may 

 be obtained in almost every running 

 brook, by damming up its upper end to 

 produce the reservoir o, and carrying the 

 pipes q q down the natural channel of 

 the stream until a sufficient fall be ob- 

 tained, for a considerable length of 

 descending pipes from o to r is neces- 

 saiy to insure the certain effect of the 

 machine, since, if the column qq is not 

 of sufficient length, its water will be 

 thrown back into the reservoir, instead 

 of entering the air-vessel, which re- 

 quires to be replenished with air, and 

 this is admitted into it by the self-act- 

 ing shifting valve, shown at b in the 

 shaded part of (Jig. 16), which is an en- 

 larged view of the air-vessel in an im- 

 proved form ; its valve is made by a ball 

 at a, having a metal bridle over it to 

 prevent its rising too high. 



In taking the height to which water 

 is to be raised by a pump, perpendicu- 

 lar height alone is to be regarded, and 

 not lateral extension, because fluids 

 press according to their perpendicular 

 height. Thus, if a pipe 100 feet long 



is six feet higher 

 the other, the six feet 

 regarded as the height to" 

 water must be raised, and the 

 may be disregarded, except so far as it 

 produces friction detrimental to the 

 motion of the water. The height of a 

 lift of water must be taken from the 

 surface of the water which is to be 

 lifted to the surface of the cistern, or 

 reservoir, or end of the pipe that is to 

 receive or deliver it, and not from the 

 bottom of the suction-pipe, because that 

 pipe may descend any distance below the 

 surface of the water to be raised with- 

 out affecting the measurement, since 

 the water will always rise to its own 

 level within that pipe, without the aid 

 of any exertion of force by the pump. 

 Be careful, likewise, to introduce no 

 right-angled or short turns into pipes, 

 if they can be avoided ; but let every 

 such turn be a regular curved sweep, 

 and the larger and more regular that 

 sweep is made, the less impediment it 

 will offer to the passage of the water. 



In order to determine the force or 

 power necessaiy to work a pump of any 

 description, the height to which the 

 water is to be raised must always be 

 taken into account; for, according to 

 what has been before stated, (col. i. page 

 11), this height multiplied into the area 

 of the piston, and reduced to any of the 

 usual denominations of weight, will give 

 the amount of resistance to be over- 

 come (friction of the pump only ex- 

 cepted). The size of the pipe contain- 

 ing the water is quite immaterial, as 

 before noticed, provided it be large 

 enough to prevent friction and unna- 

 tural velocity in the water ; and the 

 entire perpendicular height from the 

 surface of the water raised to the point 

 where it is delivered, whether occupied 

 by suction or feeding-pipe, or deliver- 

 ing-pipe from a forcing-pump, must be 

 added together and considered as the 

 height of the lift : so that if a lift and 

 force-pump of four inches in diameter 

 in the working-barrel, has ten feet of 

 three-inch suction-pipe below its piston, 

 and twenty feet of two-inch delivering- 

 pipe (including the length of the work- 

 ing-barrel) above it, the column to be 

 lifted will be equal to thirty feet of four- 

 inch-pipe filled with water. The con- 

 tents in gallons of thirty feet of four- 

 inch -pipe must therefore be found, and 

 as each Imp. gallon of water weighs 

 10 Ibs. avoirdupois, the weight or load 

 upon the pump will be immediately 

 found, to which must be added, from one- 



