Hydrostatics and pneumatics / [Dionysius Lardner].

  • Dionysius Lardner
Date:
1831
Catalogue details

Licence: Public Domain Mark

Credit: Hydrostatics and pneumatics / [Dionysius Lardner]. Source: Wellcome Collection.

    335/376 (page 319)
    all the water which is in it at any time, and, therefore, that the atmospheric pressure affords no aid to the work- ing power. i Since the action of the pump in raising water is sub- ject to intermission, the stream discharged from the spout will necessarily flow by fits and irregularly, if some means be not adopted to prevent this. At the top of the pump a cistern may be constructed, with a view to remove this inconvenience. If the pump be worked, in the first instance, so as to raise more water in a given time than is discharged at the spout, the column of water will necessarily accumulate in the barrel of the pump above the spout. The cistern M N will, therefore, he filled, and this will continue until the elevation of the surface of the water in the cistern above the spout will produce such a pressure, that the velocity of discharge from the spout will be equal to the velocity with which the water is raised by the piston. The level of the water in the cistern will therefore cease to rise. This level, however, will be subject to a small variation as the piston rises; for while the piston is descending, the water is flowing from the spout, and no water is raised by the piston, consequently the level of the water in the cistern falls. When the piston rises, water is raised, and the quantity in the cistern is increased faster than it flows from the spout, consequently the level of the water in the cistern rises, and thus this level alternately rises and falls with the piston. But if the magnitude of the cistern be much greater than the section of the pump barrel, then this variation in the surface will be propor- tionally small, for the quantity of water which fills a part of the barrel, equal to the play of the piston, will pro- duce a very slight change in the surface of the water in the cistern. The flow, therefore, from the spout S will be uniform, or nearly so. The forcing Pump. (168.) The forcing pump is an instrument which com- bines the principle of the suction and the lifting pump.