. The principles of physics. d made to do useful work. In well proportionedcondensing apparatus the pressure on the exhaust side maybe reduced 90 per cent., so that the moving piston instead ofworking against a resistance of 15 lbs. meets with a resistanceof only lbs. per square inch. 269. Steam gauge. — An instrument called a steam gaugeis connected with the boiler. It measures the excess of the 1 The terms, loiv-presn^vre and Jiigh-pressure engines, are not distinctive as appliedto engines of tlie present day. COMPOUND OR DOUBLE-CYLINDER ENGINE. 311 pressure of the steam at any instant a
. The principles of physics. d made to do useful work. In well proportionedcondensing apparatus the pressure on the exhaust side maybe reduced 90 per cent., so that the moving piston instead ofworking against a resistance of 15 lbs. meets with a resistanceof only lbs. per square inch. 269. Steam gauge. — An instrument called a steam gaugeis connected with the boiler. It measures the excess of the 1 The terms, loiv-presn^vre and Jiigh-pressure engines, are not distinctive as appliedto engines of tlie present day. COMPOUND OR DOUBLE-CYLINDER ENGINE. 311 pressure of the steam at any instant above the atmosphericpressure. The absolute pressure of the steam { measuredfrom zero) is the pressure indicated by the steam gauge plusthe pressure of the atmosphere at the time. 270. Compound condensing or double-cylinder engine. — Thisengine has two cylinders, each like that of a simple , A (Fig. 223), called, the high-pressure cylinder, receivessteam of very high pressure directly from the boiler through. Fig. 223. the orifice V. The steam, after it has done work in thiscylinder, passes through the steam-port E into cylinder B,called the low-pressure cylinder. Cylinder B is larger thancylinder A. The steam which enters cylinder B possessesconsiderable pressure, and is therefore capable of doing con-siderable work under suitable conditions. It should be bornein mind that in order that steam may do work in any cylinder,it is necessary that an inequality in the pressure of the steam 312 MOLECULAR DYNAMICS. each side of tile piston should be maintained; just as aninequality of level, a head, is essential to steam, after it has done its work in cylinder B, passesthrough a port C into a condenser (not represented in ), where it is suddenly condensed or let down to a verylow pressure. If a vertical glass tube were led from the con-denser to a vessel of mercury below, the mercury wouldordinarily stand about 25 inches high in the tube
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysics, bookyear1895
