66

Pl.XXI.Fig. 2.

Hydraulics.’

60. In the bottom Part is fixed a Pipe F O to brillsup the Water from the Mine or Well at O, which i cdelivers into the Box by a Valve at c. In the MiddRof the Piston is' likewise another Valve m opening up'wards. A L M N is a Tube or cylindric Pipe, in whichthe Water is raised to a Cistern to run oft’. ’Tis easy ^observe, that as the Piston is drawn up, the Water W>Drun in beneath, through the Valve c, to prevent a V a 'cuum ; and also, that when the Piston is forced doWrtithe Water in the lower. Parts must be forced up throughits Valve, and when the Piston is raised again, tb eWater above it will be forced up the Pipe AM t0the Cistern.

61. Another Thing peculiar to this Pump is, th eShortness of the Stroke of the Piston, which is co 0 'pensated by the largeness of its Area, and the greatsNumber of Strokes that may be made in the fartsTime. The only Objection to this Pump is, that it 15always charged with the Weight of so much Water, ^is equal to a Column of Water, whose Base is equ ato the Area of the Piston, and the Height equal to th^of the Reservoir above it, as is evident from what ^have said in explaining the Hydrostatic Paradox. ^that the Tube ALMN has no Advantage in bsirt -1small, unless any particular Circumstance or Convert 1 'ency require it.

62. Archimedes’s Screw deserves aConsideratio 11 ’not only for its Antiquity, but its Usefulness in raist 1 ^Water. It consists of along Cylinder, with an holl°jPipe, Tube or Groove Coil’d about it, as representin the Figure ; where the Cylinder is AB, and wTube C I) open at each End. It is placed in an obliQ 1 ^Position to the Horizon with the lower End in the

ter to be pump’d away, the other End being supporton the lower Part of the Winch I K, by which ^Screw and Cylinder is turned round.

63. As soon as the Screw is immersed in the

it immediately rises therein by the Orifice C, to ^Level of the Surface of the Water E F, and ifPoint of the Helix or Spiral, which in the Beginning 0the Motion is coincident with the Surface of thehappens not to be on the lower Side of the Cyli 11 ^