The mechanical effect E′ produced per minute by the steam of full pressure will be

E′ = P′AVe = Wae − AVbe;
e + c

and the effect E″ per minute produced by the expansion of the steam will by (12.) be [Pg515]

E″ = Wa log.1 + c − bVA(1 − e).
e + c

Hence the total effect per minute will be

E = Wa{e + log. 1 + c} − bVA.(19.)
e + ce + c

If the engine work without expansion, e = 1;

∵ E′ = Wa − bVA,(20.)
1 + c

as before; and the effect per minute gained by expansion will therefore be

E − E′ = Wa{e − 1 + log.1 + c};(21.)
e + c1 + ce + c