THE INTERNAL COMBUSTION ENGINE
It will be observed that in a steam engine the heat is developed outside of the cylinders and the latter used solely for the purpose of taking the steam and utilizing it, by causing its expansion to push a piston to and fro.
We shall now consider that type of motor which creates the heat within the cylinder itself and causes an expansion which is at once used and discharged at the reciprocating motion of the piston.
The original method of utilizing what is called Internal combustion Motors, was to employ a fixed gas. A fixed gas is one which will remain permanently in that condition, unlike a vapor made from gasoline. The difference may be explained as follows:
Fixed Gases.—If the vapor of gasoline, or petroleum, is subjected to a high heat, upwards of 1500 degrees, it is so changed chemically, that it will not again return to a liquid state. This is called fixing it. Gas is made in that way from the vapor of coal, and fixed, producing what is called illuminating gas.
Although the temperature of fixing it is fully three times greater than is required to explode it, the fact that it is heated in closed retorts, and oxygen is prevented from mixing with it, prevents it from burning, or exploding.
Gas Engines.—Such a gas has been used for many years in engines which were usually of the horizontal type, and were made exceedingly heavy and cumbrous, and provided with enormous fly wheels. Gases thus made are not as rich as those generated direct from the hydro-carbon fuels, because, being usually made from coal they did not have a large percentage of hydrogen.