Chapter XXXVII.—THE STEAM ENGINE.
The high pressure steam engine, in whatever form it exists, consists of a frame or bed plate carrying two distinct mechanisms, first, the driving or power-transmitting mechanism, and second, the valve gear or valve motion, and to these are added such other mechanisms as the nature of the duty the engine is to perform may require.
The most prominent of these additional mechanisms is a governor for regulating the speed at which the engine is to run; nearly all steam engines require a governor in some form or other, while for electric lighting and some other purposes it constitutes the main feature in the design of the engine.
In a locomotive the air brake and the sand box are elements not found in other engines.
In a jet condensing engine, the condenser and injection water, or condensing water mechanism, is a part of the engine.
In a surface condensing engine, the air pumps and circulating pumps are a part of the engine.
In marine engines there are mechanisms for turning the engine around when no steam is up; for moving the reversing gear quickly, and for varying the point of cut off, and therefore the amount of expansion, and various other and minor mechanisms.
