HYDRAULIC POWER

AND

HYDRAULIC MACHINERY.

THE ELOW OP WATER EHSTDER PRESSURE.

The weight of distilled water of maximum density is 62'499 lbs.at 39° Fahrenheit. The density diminishes towards the freezingpoint at which (in the form of ice) a cubic foot only weighs58 lbs. Ordinary fresh water weighs 62J lbs. per cubic foot,and sea water 64 lbs. Although water has been proved byexperiment to be compressible (but very slightly) under greatpressures, for all practical purposes it is taken as incompressible.The compressibility of water is one twenty-thousandth for anincrease in pressure equivalent to an atmosphere.

The conditions which govern the flow of water through pipes,and into or out of closed vessels, have been the subject of Ob-servation and experiments dating from Torricelli ’s time to thepresent, but only a brief reference to them can be attempted.The investigations of Torricelli , Yenturi, Bernouilli, Eytelwein,Darcy, Weisbach, Du Buät, Prony, Bazin, and more recentlyof Rankine, Downing, Reynolds, Unwin, Cotterill, Hamilton-Smith and others are published, and are available for those whowish to pursue the subject in detail.

Torricelli discovered in 1643 that the velocity of a fluidflowing through an orifice in a vessel, is that which a solid body