“How is steam utilised by the locomotive?” is a question asked again and again (and not by children only) ever since Stephenson’s engine started on its triumphant progress from Stockton to Darlington and back, and which, I venture to affirm, only a small percentage of travellers, even in 1903, can answer “right away,” as our American cousins would express it.
Briefly, then, as follows: Raised up on high is the mighty boiler. Remove its plates, and running through its entire length will be seen a cluster of some two or three hundred brass tubes, in diameter that of a penny-piece. At the rear of the boiler, on a lower level, is the fuel fire-box, with its grate and ash-pan, while in front is the smoke-box, surmounted by the familiar chimney or funnel, called in the United States the “smoke-stack,” in British engines reduced to a minimum of height. Water from the tender surrounds the brass tubes, and when the fire is burning, flames, smoke, and heated gases rush through them, escaping viâ the chimney, but in their passage converting the boiling water into expanding steam, which, when the regulator is opened, is directed by valves into the hollow cylinders—sometimes placed below the boiler, but generally visible outside—forcing by its pressure the pistons backwards and forwards alternately, and, by means of intermediate machinery, transferring its energy to the driving-wheels.
The exhausted steam, after accomplishing its work, joins the smoke in the smoke-box, escaping up the funnel by jerks, which creates a forced draught through the brass boiler-tubes, and hastens the generation of steam.
ELECTRICITY—THE NEW ORDER
Contrast this with electricity, the definition of whose exact nature is a task I must of necessity leave to others, but its adaptation to the purposes of traction can be thus broadly explained:—
Dynamos or generators are situated at some fixed station, more or less distant, generating electrical energy, whence the current is transmitted along a central steel rail, or, in the case of some tramways, viâ overhead wires, returning to its place of birth by another rail or cable, and completing its circuit. It is “picked up” by a small locomotive fitted with motors that work the driving-mechanism, and thus propels the coaches or cars behind it at varying speeds.
The rotation of the dynamos is effected either by a torrent, waterfall, or swift-flowing river, absorbed by turbines, or by steam supplied from ordinary boilers.
In other words, we convert our water and coal into steam, and, indirectly, the heat in the steam into electrical energy; and the heavy locomotive that used to carry its own fuel, and manufacture its steam as it tore along with the train behind it, now leaves tender and boiler at home, and has its driving power, in the form of electric current, forwarded to it per centre rail, to be drawn upon when wanted.
The system is beautifully simple, and the machinery compact and uncomplicated. Smoke defilement is unknown, and the trains are comparatively noiseless. In short, electric traction is the refinement of mechanically applied power.
Now let us visit an electrical power station—a small one—and I have in my mind that of the Waterloo and City Electric Railway.