GAS-ENGINE
740
GATES
Otto brought out the present four-stroke cycle engine. It was a reinvention of an engine which had been patented in 1862 by Beau de Rochac, but had not been successfully introduced. In the Otto engine the mixture of air and gas is drawn into the cylinder during the second stroke; it is here exploded and during the third stroke expands; on the fourth and return stroke the cylinder is cleared for a new charge. This was the first gas-engine used extensively, and all the practical gas-engines of to-day show no marked departure from the Otto four-stroke cycle. The ignition of the mixture at the proper instant may be done
fuel than ordinary illuminating gas, it is claimed that gas-engines compete with steam-engines for all-day loads. Recently the vapors of gasoline and petroleum have come into successful use as fuel for such engines. The oil-engine differs from the gas-engine only in being provided with some sort of vaporizer whereby the oil is converted from a liquid to a gas on its way to the cylinder. One of the remarkable exhibits at the Paris exhibition of 1900 was that of large gas-engines. The largest gas-engine at the Chicago world's-fair in 1893 was one of 35 H. P. At the Paris exposition of 1900 there was one
A GAS-ENGINE
by an electric spark, but is often done by a small gas-jet and a heated ignition-tube. The speed is generally regulated by a centrifugal governor (see GOVERNOR, ENGINE) which controls the supply of gas. Within a few years the use of gas-engines has increased very rapidly. Their adaptation for small powers was evident immediately. Even if the fuel-cost be greater than for a steam-engine, this is more than balanced by the convenience and economy in attendance. Then the gas-engine is costing nothing for fuel when it is at rest, so that it is specially adapted for places where power is only needed a fraction of the day.
But the efficiency of gas-engines in transforming the heat-energy of the fuel into work is from 20 to 25 per cent., twice that of small steam-engines, and, with cheaper
engine of 1,000 H. P., and gas-engines giving a hundred H. P. or more were shown to be very common in practice to-day.
The gas-motor of Mr. R. Diesel has attracted a great deal of attention from engineers. In the Diesel motor the compression of the mixture (vapor or gas) which was the feature of the Otto engine is carried still further, even to the point of raising the temperature of the mixture to ignition. Tests of this engine give the highest efficiency of any form of heat-engine, but the engine has not yet come into general commercial use.
A. P. CARMAN.
Gates, Horatio, an American general, was born in England in 1728, and, entering the British army, was an officer under Braddock, at whose defeat in 1755 he was
