But there are other kinds of non-illuminating gases--such as Wilson's,
Strong's, and Dowson's--which are now coming into use; and at Messrs.
Crossley's works you will have an opportunity of seeing a large
engineering factory employing several hundred mechanics, and without a
chimney, in which every shaft and tool is driven by gas-engines
supplied by Dowson's gas, and in which the consumption of coal is only
1.2 lb. per indicated horse power. The greatest economy ever claimed
for the steam-engine was a consumption of 1.6 lb.; and this with steam
of very high pressure, expanded in three cylinders successively. Thus
in a quarter of a century the gas-engine has beaten in the race the
steam-engine; although from Watt's first idea of improvement, nearly a
century and a quarter have elapsed.

As regards the steam-engine, it is the opinion of competent
authorities that the limits of temperature between which it works are
so restricted, and so much of the heat is expended in producing a
change of state from liquid to vapor, that little further improvement
can be made. With respect to gas-engines, the limits of temperature
are much further apart. A change of state is not required, and so very
great improvement may still be looked for. It is not impossible even
that some of the younger members of our body may live to see that
period foretold by one of the greatest of our civil engineers--that
happy time when boiler explosions will only be matters of history;
that period, not a millennium removed by a thousand years, but an era
deferred perhaps by only half a dozen decades, when the use of the
gas-engine will be universal, and "a steam-engine can be found only in
a cabinet of antiquities."