W = the water in cubic feet admitted per minute in the form of steam through the steam valve.
S = the number of cubic feet of steam produced by a cubic foot of water.

[Pg514]

Hence we shall have

WS = VA (1 + c);
∵ S = VA(1 + c).(15.)
W

Since by (10.) we have

P = a − b;
S
∵ P = Wa − b.(16.)
VA(1 + c)

By which the pressure of steam in the cylinder will be known, when the effective evaporation, the diameter of the cylinder, and speed of the piston, are given.

If it be required to express the mechanical effect produced per minute by the action of steam on the piston, it is only necessary to multiply the pressure on the surface of the piston by the space per minute through which the piston moves. This will give

VAP = Wa − VAb;(17.)
1 + c