FIG. 7.
FIG. 9.
FIG. 10.
As it is necessary that trains should at certain places be “shunted” or shifted from one line of rails to another, particularly at stations where a great many tracks run side by side, and cross each other to branch off to different parts, there are arrangements called “points,” shifted by a lever or “switch,” so that they shall direct the course of the train, and cause it to leave the former track and enter upon a new one; this arrangement may be seen at [fig. 5], where the points are in the position to direct the engine coming in the direction of the arrow on to the curved line A, and the dotted lines indicate the position into which they would be shifted, if necessary for the train to go straight on to the line B; this action is effected by moving a lever which shifts the two bars a few inches either way. When an engine or carriage has to be turned on to a track at right angles to the one on which it rests, or where there is not room for “shunting,” an apparatus called a “turn-table” is used, which is shown at [figs. 6] and [7]; it is a round platform of iron turning on its centre, and supported by friction rollers at the edge, having on its surface raised rails in two or more directions, so that it may be turned round half or quarter distance, according to the position required. The engines and carriages used to run on railways are of various constructions, but to a certain extent agree in their chief particulars; the wheels are fixed to their axles, so that each pair and the axle which joins them may be considered as one piece.The axle projects a little way beyond the wheel, and on this part it supports the engine or carriage, which is wider than the distance from one wheel to its fellow. They are therefore entirely underneath. They are of iron, made by machinery and have a projecting edge on the inside of the “tire” of each, which is called the “flange” (see [fig. 8]); this flange does not run on the rail but within it to prevent the wheels from slipping off. These flanges, when the pair of wheels and axle are united, exactly fit in between the rails, so as to touch the inside of each and form a sort of guide. Each carriage has two pairs (except in a few cases, where three pairs are used), the engines have usually three, and sometimes four pairs. The carriages rest upon powerful springs, and are moreover furnished with springs to diminish the concussion of one carriage against another; these last are acted on by a sort of piston-rod, one of which is placed at each corner of the carriage, and are called “buffers” ([figs. 9] and [10]); they all coincide with each other, and form a set of springs all along the train, which greatly reduces the shock which would otherwise be felt when it is stopped. Another set of springs is connected with the binding screws which unite each carriage, and these prevent the sudden jerk which would result from the starting off of a train quite inelastic in its length.
The engines used are of that class called high-pressure or non-condensing, and there are two cylinders and pistons, which have a stroke of about eighteen inches. The boiler is so contrived that a large quantity of steam shall be rapidly produced; for this purpose tubes of brass are made to pass side by side from the fireplace through the boiler, and through these tubes the flame and hot air must go before reaching the funnel, giving out in its course a great amount of heat to the water and converting it rapidly into steam. The steam from each cylinder passes at each stroke of the piston into the funnel, assisting to form a draught which draws the flame from the fire through the tubes and increases the fierceness of the combustion. The necessity for two cylinders and pistons is owing to the impossibility of having a fly-wheel, and as the driving wheels of the engine have to be turned at an equal rate, the axle has two cranks so placed that the greatest power of one piston is exerted where the other exerts the least (see “[Steam-engine]”).
FIG. 11.
