From Horace Darwin to G. H. Darwin 21 October [1875]

Dear George

I enclose all I can find out. Try Haughton on efficeincy of animals. I might ask the manager if this is not enough. You could find out what men eat, from some medical book & how much they work by Rankine & calculate efficiency

H Darwin

The average duty of the Pumping engines of Cornwall is 3.1 lbs of Welch coal per actual horse power per hour.

Bournes Steam Engine

p 121

But some engines reach a duty of 1.74 of Welch coal per actual h.p. per hour   Bourner Do.do. do

See Rankine Steam Engine p 84 for work done by animals

See Rankine Steam Engine p 278 for heat given out by different coals.

You might find something in Recent Improvements in the Steam Engine

By F. Bourne