Note 466 — Chapter XV

It may be stated, generally, that 1 lb. of coal can, under the most favourable circumstances, be made to evaporate from 12 to 16 lbs. of boiling water, the evaporation of each pound being equivalent to 745,800 foot-pounds of mechanical work. At this rate 1 lb. of coal ought to give out from nine to twelve million foot-pounds of work, while, in reality, no steam-engine does so much as two million foot-pounds for a pound of coal, so great is the loss from the want of proper means of utilizing the whole work produced by the combustion of the coal.—Vide Text-Books of Science, p. 174; by C. W. Merrifield, F.R.S.