Note 16 — The Correlation of Vital and Physical Forces.
Reading edition
Rankine (The Steam-engine and other prime Movers, London, 1866,) gives the efficiency of Steam-engines as from 1-15th to 1-20th of the heat of the fuel.
Armstrong, Sir Wm., places this efficiency at 1-10th as the maximum. In practice, the average result is only 1-30th. Rep. Brit. Assoc., 1863, p. liv.
Helmholtz, H. L. F., says: “The best expansive engines give back as mechanical work only eighteen per cent. of the heat generated by the fuel.” Interaction of Natural Forces, in Correlation and Conservation of Forces, p. 227.