The construction of an ordinary steam locomotive is an intricate operation, necessitating machine-shops, erecting-shops, foundries, forges, etc., covering acres of ground, as at Crewe, Doncaster, Derby, or Swindon. Not a hundred engines are exactly alike in pattern, and each one is supposed to be composed of over five thousand different parts, all of which have to be stowed away in a necessarily limited space. “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.