136

MODERN STEAM PRACTICE.

of the cylinder, so that when one of them is shut the other is open tothe indicator, and so on for each end of the cylinder. The examples

High-pressure Cylinder.

Steanij 54 lbs. Vacuum, 28^ inches. Revolutions, 60.

Indicated horse-power, 457 66 H.p. cylinder.Do. do. 713-75 l.p. „

II 7 I 4 1

Low-pressure Cylinder.

Figs. 80, 81.— Compound Engine Diagrams.

illustrated are taken from combined engines of the vertical type;the top and bottom of the cylinders are taken in the literal sense,but the IN stroke of all engines—that is, when the crank is movinginwards towards the cylinder—should be termed the IN stroke, andwhen the crank is moving from the cylinder the OUT stroke issignified: by adhering to these terms confusion is prevented.

Although the two preceding examples show back pressure onthe return stroke of the high-pressure piston, as delineated by thediagrams, yet the expansion may be carried so far that the steammay fall to the atmospheric line at the commencement of the strokeof the large piston or low-pressure cylinder. The following dia-grams show that this has taken place in the up or top stroke of thehigh-pressure piston, the steam expanding to the top of the large