The Steam Engine Explained and Illustrated (Seventh Edition) / With an Account of Its Invention and Progressive Improvement, and Its Application to Navigation and Railways; Including Also a Memoir of Watt

by Dionysius Lardner

The logarithms in these formulæ are hyperbolic.

To apply these principles to the actual case of a double acting steam engine,

Let

L = the stroke of the piston in feet.

A = the area of the piston in square feet.

n = the number of strokes of the piston per minute.

∵ 2nAL = the number of cubic feet of space through which the piston moves per minute.

Let

cLA = the clearage, or the space between the steam valve and the piston at each end of the stroke.

∵ The volume of steam admitted through the steam valve at each stroke of the engine will be 2n AL(1 + c).

Let

V = the mean speed of the piston in feet per minute,

∵ 2nL = V.

The volume of steam admitted to the cylinder per minute will therefore be VA (1 + c), the part of it employed in working the piston being VA.

Let