68

Hydraulics.

Pi.XXi.Fig. 4-

Fig. 5-

other. Now when the Piston is drawn up from B to Fta Vacuum will be made between, bat the Valve B W>Hnot rife by the Water below it; for the Water in th ePart B C cannot rife itself, much less can that in th 6Part C D below it, as being prefs’d with the Weightthe Column above, and its own Weight downwards?therefore no Part of the watery Column B F can moV®of itself, or by itself. Now no Power can be applss 3any where but at E to move the whole Column ; n° (can the whole be moved without raising all the VaM 5at once ; therefore the Power able to raise the Valve ^E, and consequently the Valve at B, must be able toovercome the Pressure of a Column of Water 6o Fe £thigh : But the Air can sustain a Column only of 3,3Feet high ; therefore the Air cannot raise the Valve Ftnor any of the rest ; therefore the Water cannot rise tOthe Barrel A B of a single Pump. .

67. However, we may raise Water by a compound

Pump, such as is represented in the Figure, where Ais the Rod of the Piston, , which at B is divided in t0two, one of which goes to the Barrel D E, and dra^ 5up the Water from the Cistern EF ; the other P 3 '.B C goes down to the said Cistern, where it is dividesat C into two other Parts ; one going to the Pump Fsupplies the Water to the Cistern E F ; the other P 3 ^C H goes to another Pump I K below, and drawsthe Water from K to the Cistern HI. Now th e *Pumps all working at once,, will draw Waterany Depth, provided each Pump does not exceed 3 2Feet in Height. ,

68. I shall conclude this Subject with an Account °,one othtr Method of raising Water, by the natttrflJgency of Heat and Cold only. It is as follows, A "C D is a pretty large Vessel filled with Water to tF eHeight E F, the Space above being possefs’d of Ass'

On the Upper Part of the Vessel is a tall Tube inserss 1G H, and descends below the Surface of Water to AOn the nether Part is another Tube or Pipe I W.

each Tube is a Valve opening upwards, as at I andThe Body of this Instrument being nicely closed ev^vWhere, so that no Air can escape, and placed with tjsslower End in the Watej- W, and thus continued in c ,

W