921 



RAILWAY. 



RAILWAY. 



822 



duction of springs and buffers to diminish the violence of the blows 

 they receive, or the effect they themselves might produce upon the 

 rails. Elasticity in the traction is also necessary as well for the safety 

 and comfort of the passengers, as for the preservation of the carriages ; 

 and even in order to economise engine power, for if it did not exist, 

 the engine would be obliged to exercise a greater power to start the 

 trains than it would do for the maintenance of the speed once attained. 

 Various contrivances, more or less successful, have been adopted to 

 secure these conditions ; but the system represented in Fly. 17, is the 



Fig- 17. 



(Htn 



one usually adopted ; it represents the plan of the framework of a 

 carriage, the body being supposed to be removed. The frame is 

 carried on springs fixed outside the wheels, and resting on brass 

 bushes, which bear directly on the axles : a, a, a, a, are the buffers, or 

 discs of wood or metal, covered with cushions, and fixed to the ends of 

 metal rods, working between guides against the ends of very strong 

 horizontal springs c, c. In such cases, when the train is suddenly 

 stopped, the springs are forced against one another, and serve thus to 

 soften the blow to an extent dependent upon the force of the spring. 

 The draw-bars are also' attached to the centre of the horizontal springs, 

 and thus prevent any sudden jar to the frames of the carriages at their 

 starting, and the several draw-bars of a train are attached to one another 

 by a coupling chain, bearing a double thread, so as to force the buffers 

 into close contact; loose chains are also placed by the sides of the buffers, 

 in case the coupling chains should break. Many varieties of springs 

 have been applied for both the purposes described above ; but experi- 

 ence has led engineers to resort to the old-fashioned plate springs, of 

 course of considerable thickness, and of the very best quality of steel. 

 The ordinary first-class carriages have three compartments, able to 

 contain from six to eight passengers in each compartment ; the second- 

 class carriages mostly have three or four compartments with ten pas- 

 sengers in each compartment; whilst the third-class carriages are 

 made to contain from fifty to sixty passengers each. The weight of 

 the best modern first-class carriages, on the narrow-gauge, is about 

 i; that of the second-class is about 6{ tons; and that of the 

 third-class 6 tons : or, in other words, the ratios of the dead weights 

 of the carriages to the loads transported are, in the several classes, as 

 2'9 to 1 ; as 2*1 to 1 ; and as 1'6 to 1. A certain number of the car- 

 riages in each train is made with breaks, and a guard's van, with occa- 

 sionally an extra luggage van, are added. Horse-boxes, carriage-tracts, 

 and post-office waggons are made upon the same principles of framing 

 and suspension, as the ordinary traveller's carriages, so as to allow of 

 th.-ir being added to the same trains as the latter. As the goods 

 waggons do not travel at the same velocity as the waggons for the 

 conveyance of passengers, there is not the same attention paid either 

 to their modes of suspension, or to their draw-bars ; but every waggon 

 which is added to a train moved by a locomotive engine is hung upon 

 springs, even when there is no spring draw-bar ; there is very rarely 

 any buffing apparatus attached to merchandise waggons. On ordinary 

 narrow-gauge lines the weights of goods carriages range between 3 

 and 5 tons ; they carry about 5 tons each. 



As there is now almost a certainty that the broad gauge will be 

 abandoned, it is only necessary to observe that upon that system the 

 carriages are not only more expensive, but that the ratio of the dead 

 to the useful weight is even more unfavourable than the one which 

 prevails upon the narrow gauge lines. It may also here be added that 

 upon almost all the continental lines of railway the carriages are much 

 more commodious than they are upon the English lines ; and that in 

 America only two classes of carriages are admitted, one for the white 

 pamengerx, the other for merchandise and negroes. The American 

 carriages usually ran on eight wheels, coupled by what are called bogie 

 frames in two pairs, in order to diminish the length of the tangential 

 line formed by the fixed axles with the curves of the roadway they 

 travel over ; the wheels, however, are very small. 



\Vr have already seen that, during the gradual development of the 

 railway system, there has been a constant tendency on the part of 

 machine-makers to increase the power and the weight of the locomotive 

 engine, until it has at last attained the colossal dimensions In-fore 

 stated. Originally also the locomotives were made with only four 

 wheels; but the frightful accident on the Versailles line in 1842 raised 

 to strong a prejudice against engines of that class, that they have been 

 universally abandoned. Six-wheeled engines are now the only ones 

 nsd on our English railways; sometimes with the tenders attached to 



the engine, and upon the same frame; and sometimes with the tenders 

 entirely detached, and carried upon a distinct set of four wheels, as is 

 the case with any ordinary carriage. In America, and on the lines in 

 Germany with very steep gradients, the engines are made with eight, 

 or even with ten wheels ; the tenders being, in either of those cases, 

 upon the same frame as the engines, but the wheels working upon two 

 bogie axle frames. In ordinary passenger engines the cylinders are 

 placed internally, and the piston-head communicates motion directly 

 to the crank upon the large centre wheels, which thus become the 

 driving-wheels, leaving the fore and hind pairs of wheels simply to act 

 as trailers. Figa. 18 and 19 will convey a tolerably correct notion of 



rig. is. 



Fig. 10. 



the engines thus referred to ; and in them a represents the fire-box, 

 usually made of copper, and surrounded by an outer casing of iron, so 

 as to leave a space all round surrounded by water ; b represents the 

 boiler, with ita horizontal tubes of about 140 or 150 in number, and 

 made of brass, passing from the fire-box to the smoke-chamber, c ; 

 d represents the steam-chest, which in modern engines is made con- 

 siderably smaller in proportion than it used to be. The steam passes 

 through the smoke-box to the cylinders at e, and there is upon the 

 tube which so conveys it a throttle valve, under the control of the 

 driver ; / and g represent the safety valves, and i the feed-pipes from 

 the engine to the tender ; h represents the steam-whistle. Until very 

 lately all locomotive engines were heated with coke, but a notable 

 economy has been obtained on some lines by the substitution of coal 

 for coke, by means of some alterations in the fire-boxes and the grates. 

 The escape-steam in all locomotives passes off through the chimney 

 above the smoke-box. On some lines of railway the cylinders, instead 

 of being placed inside the frame, are placed externally to it, so that the 

 motion is communicated at once from the piston through the crank to 

 the driving axle, without the necessity for forging a crank on the 

 axle itself ; but there seems to exist a great disinclination on the part 

 of the majority of engine builders to adopt this simple arrangement, 

 perhaps on account of the condensation which takes place in the 

 cylinders, and on account of the frequent ruptures of the cylinders 

 which occur in these engines. The driving-wheels of ordinary express 

 locomotives, on Cramptou's system, are now made 8 feet in diameter; 

 the cylinders about 18 inches diameter, and 2 feet stroke ; the heating 

 surface in the fire-boxes is about 154 feet superficial, and the heating 

 surface of the tubes about 2200 feet ; the pressure of the steam is 

 often 120 pounds on the square inch. Such an engine, with its tender 

 filled with coke and water, would, at a maximum, weigh 36 tons ; the 

 trailing or carrying-wheels are 3 feet 6 inches in diameter. 



