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Hydraulics. 45

IH. IV. But the most confidfitabie o£

all Water-Engines is that call’d New-

Jham’s

Properties of the inverted Syphon, or Fountain, describ-ed m Anmu LXXIII. Art. i'i, 12, 13, H'. jABCDEFG represent the inverted Syphon there de-scribed i Only here the Part ABCD represents a Co-lumn of Air, and DG the lower Part of the Pipe of at* Um P immersed in the Water of the Well H I. Get5 be the Piston of the Pump at E in its lowest Situa-tl0n , and at F in its highest. Now as both these Partscommunicate with the°Water, one by pressing on it,the other by opening into it, they may be looked upon

as communicating with one another. .

2. Now ABC, the Column; of Air, would by its,eight or Pressure force up a Column of Water intothe Pipe D G to the Height of 33 Feet, were the Airexhausted from the'said Pipe, and continued to thatHe >ght; (the Weight of a Column of Atr bemgequsc the Weight of such a Column of Water of the laJ*se, as will be strewn hereafter.) If nmv the Piston Pbe thus thrust down'to E, meeting the Water there,a »id f rom thence it be raised to F with an uniform Mo-tion, the Water will rise from E to follow the PistonWith a variable Velocity; the least: of which i s as yfACV^DE, and the greatest as %/AC—DE — y/ABr

(by Annotation LXXIII. 12.)

3- If in lifting up the Piston the Velocity of Water

be less than that of the Piston, it will not. be able totollow it, hut will leave a void Space between them,)ybich will increase more and more as the Velocity 0Water becomes less than that of the Piston. I“ esconfequence of this will be, that a Part of the Strokeof the Piston will be lost; and not only that, but the-iston, when the Water leaves it, will rife very hard,as having the Weight of Water upon it, and the Airm greater Density above than below; whence t eEquilibrium, which ought to be in Pumps, is destroy-ed, and the Balance against the WArkmen. ^Now ascsn h-annfm the Di&niCter of tllS

of

fe-

ed, and the Balance against the w raw--"

Bus can happen where the Diameter of the ■-Pipe is equal to that of the Pump-barrel, muc -