a comparison between the actual cost of large steam engines and that of
gas motors of similar size.

Take a good Galloway or multitubular boiler; for 75 horse power
effective the heating surface must be at least 74 square feet. Using
good Cardiff coal, with 4 per cent. of ash, and a heating power of
15,660 Fahr. units; the steam raised will be 8 to 9 pounds per pound of
coal, so that 9,400 to 10,577 Fahr. units are utilized in raising steam,
or 68 to 76 per cent., which is an excellent result. Take an engine of
16 inch cylinder diameter, 40 inch stroke, and 66 revolutions, etc.; it
will use 22.4 pounds of steam per horse power effective, which
represents 2.47 to 2.8 pounds of coal under the boiler. These 10 pounds
of steam carry 11,752 Fahr. units of heat, and produce work equal to 75
horse, or 1,143 Fahr. units of heat; which corresponds to an efficiency
of 9.7 per cent. In a gas motor, on the other hand, we find the
materials employed, as per the above data, to contain 8,958 Fahr. units
of heat, and to make gaseous fuel in which 6,343 units are available; a
return of 70.6 per cent, in the producer. The motor receives these
6,343, and converts 1,143 of them into work; an efficiency of 18 per
cent. In order to be equivalent from the heat point of view, a steam
engine ought to produce a horse power effective per 9.72 pounds of steam
at 5 atmospheres; but no such steam engine exists.

M. Witz goes on with comparative estimates. For a Corliss engine and
boiler, with chimney, etc., complete, and putting these up, he allows
£1,280; for a Simplex gas motor and Dowson producer complete, including
putting up, he allows £1,290, which he explains to be average actual
prices; but these prices do not cover cost of transport, and M. Witz
does not go into cost of masonry for buildings, apart from foundations,
etc., for the apparatus and machinery.