OF RAIL-ROADS.

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Fig. I. Plate IV. will convey a pretty correct idea of themode of action of this kind of engine. R R is a piece ofiron of the rails constituting the Rail-road, on the side ofwhich are cast the semicircular protuberances or projections1.11. &c. these semicircular teeth project from the side ofthe rail two or three inches, thus forming a longitudinaltoothed 'rack, which is extended the whole length of theroad, a a are the cylinders, placed within the boiler.The action is communicated by the pistons to the con-necting rods b b, which transfer the motion to the cranks c c,turning upon axles attached to the frame of the carriage.Upon the axles on which these cranks are fixed, are alsofixed the pinion-wheels d d, which are turned round by thecranks ; these two pinion-wheels communicate with a largercog-wheel, e, in such a manner that both contribute in pro-ducing a rotatory motion in it. The axle of this cog-wheel,e, extends to the outside of the frame of the engine, and uponthe end of it is affixed the larger toothed wheel f, which isthus turned round by the large cog-wheel, and consequentlyby the action of the engine ; and the teeth of this cog-wheelbeing made to correspond, will lay hold of the toothed pro-jections on the side of the rail, a progressive motion of thecarriage is thereby effected. The steam, after performing itsoffice in the cylinder, is allowed to escape into the atmo-sphere, through the pipe e. The boiler is cylindrical, and isheated by a circular tube passing through it, terminated atone end by the chimney. The toothed or rack-rail is onlylaid on one side of the road, the other being common rails.The cog-wheels can be varied in size according to the dif-ferent velocity with which it is required to travel.

By the use of this rack-rail the engine isenabled to ascend acclivities which Mr. Tre­ vithick ’s engine, from the want of adhesion,

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