Compound Engine

—A steam engine in which the steam is expanded in two stages, thus reducing the range of temperature in the cylinders, and making the turning effort more uniform. The cylinder of the first stag? of expansion is termed a high pre ure cylinder, the larger or second one the low pre ure. Sometimes a compound engine has three cylinders; one high pre ure exhausting into two low pre ure cylinders. This type should not be confounded with a three cylinder triple expansion engine in which the steam pa es from the high to the intermediate, thence to the low pre ure cylinder.