This economical advantage of the gas over the steam-engine holds good for higher power as well, and becomes
even more marked when producer-gas is used instead of street-gas. Comparing, for example, a 50 horse-power steam-engine having a pressure of 90 pounds and a speed of 60 revolutions per minute, with a 50 horse-power producer-gas engine, and considering in the case of the steam-engine the cost of a boiler of suitable size, foundation, firebrick, smoke-stack, etc., and in the case of the gas-engine the cost of the producer, foundation, and the like, it will be found that the installation of a steam-engine entails an expenditure 15 per cent. greater than in the case of the producer-gas engine. However, the cost of operating and maintaining the steam-engine of 50 horse-power will be 40 per cent. greater than the operation and maintenance of the producer-gas engine.
From the foregoing it follows that from 15 to 20 up to 500 horse-power the engine driven by producer-gas has considerably the advantage over the steam-engine in first cost and maintenance. For the development of horse-powers greater than 500, the employment of compound condensing-engines and engines driven by superheated steam considerably reduces the consumption, and the difference in the cost of running a steam- and gas-engine is not so marked. Still, in the present state of the art, superheated steam installations entail considerable expense for their maintenance and repair, thereby lessening their practical advantages and rendering their use rather burdensome.
FOOTNOTES:
[A] Recent improvements made in suction gas-producers will probably lead to the wide introduction of producer gas engines even for small power.
CHAPTER II
THE SELECTION OF AN ENGINE
Explosion-engines are of many types. Gas-engines, of the four-cycle type, such as are industrially employed, will here be principally considered.