790 



RAILWAYS. 



1 .u! ; u!><! '.vhrre tiie rail is supported at successive 

 I'oinus by rnairs, it is always intended to be of such 

 strength, lliat it wiiJ not be sensibly bent by the 

 weight. Continued lines of granite or other durable 

 . are now in use on a number of railroads in 

 tin- Tinted States of America, but cannot as yet be 

 considered to be so thoroughly tested, though the 

 results of the experiments are thus far very favour- 

 able. It was apprehended, at first, that the action 

 of the wheel would draw or flatten the iron plate; 

 but it has been lound by experience, that this effect 

 is not produced. The principal difficulty in the use 

 of this kind of track, was in the fastening of the rail 

 to the stone, the nails used for this purpose being 

 lialile to be loosened or cnt off by the expansion 

 and contraction of the iron rail. This defect has, 

 however, been partially remedied by making oval 

 holes in the rails for the fastenings, thus allowing a 

 iittle longitudinal motion of the rail without injury to 

 the fastenings. Cast iron rails do not so easily 

 bend, and the same weight of iron is also much 

 cheaper. But they are more subject to be broken by 

 sudden jars and blows, and a much greater weight 

 must be used in order to obtain therequisite strength. 

 In the tram railways, plate rails are used, with a 

 perpendicular plate or rim, at the outside edge of 

 the rail, of two or three inches in height, to confine 

 I he. wheels upon the railroad. In the mode of join- 

 ing the rails, very important improvements have been 

 made since the introduction of railroads into more ge- 

 neral use. The rails were at first only about three or 

 three and a half feet in length, and fastened in the 

 chairs by a pin running horizontally through each 

 end of the rail, there being two holes in each chair for 

 the admission of two pins for this purpose, one for the 

 end of each rail, so that the fastenings were distinct. 

 The consequence was, that if the chair did not 

 stand upon a perfectly firm foundation, but upon 

 one that yielded on one side, so that the chair 

 leaned in the line of the road, one of the pins, and 

 consequently the end of the rail fastened by it, 

 would be depressed below the other, thus making 

 u sudden break in the surface of the track, which 

 would cause a jolt as the wheel passed over it, to 

 the injury of both the road and the carriages, 

 and the inconvenience of passengers. Mr Wood 

 says this defect was very frequent on rail-roads 

 constructed upon this plan. It has been remedied 

 by making the rails join by lapping with what is 

 called the half-lap, and fastening the ends of both 

 rails by one pin ; so that, although a chair should 

 lean in the line of the road, or be a little depressed 

 below the others, still the two rails would present 

 a smooth surface at their junction. The injury and 

 inconvenience occasioned by the imperfections of 

 the junctions of the rails were still further remedied 

 l>y making the rails twelve or fifteen feet in length, 

 supported at short distances as before, the form and 

 dimension* of each part of the rail between any 

 two supports being constructed as already described; 

 by which means the number of junctions was re- 

 duced to one fourth or fifth of their former number. 

 This was a very great step in the improvement of 

 this species of road. An improvement, of great 

 utility, has also been made in the mode of fastening 

 the rails, by dispensing with the use of pins, which 

 were liable to work loose. There are various 

 forms of constructing the rails and chairs for this 

 purpose, but they all agree in principle. One 

 mode is by making a depression in the chair on 

 one side of the rail, into which a projection from 

 its lower side precisely fits. If the rail is held close 

 upon that side, it is thereby fixed to the chair, and 

 can be moved only with the chair itself; and it i> 

 M> held by driving a key or wedge along the 



opposite side of the mil, between the rail and Ihe 

 side of the chair projecting upon the side of the 

 rail. 



Ckatrs. Fastenings. In describing the rails, 

 tin- supports or chairs have been partly described. 

 They are of iron, with a broad, flat base, supported 

 upon blocks of stone, into which holes are drilled, 

 and filled with wooden plugs. The chairs are 

 fastened to the stone blocks by nails driven into 

 these plugs. This stone block should rest firmly 

 upon its base, and not be liable to change of posi- 

 tion by frost or any other cause ; and, accordingly, 

 great care has been taken to make these supports 

 firm. 



Turn outs. If all the wagons upon a rail-road, 

 whether tor the transportation of passengers or 

 merchandise, were to travel at the same time, and 

 at the same speed, two sets of tracts would be suf- 

 ficient to accommodate the whole, as there would be 

 no necessity of their turning out to pass each other. 

 But in the transportation of passengers, greater 

 speed is desirable than in the transportation of 

 merchandise ; for the transportation of merchan- 

 dise, whether by horse power or steam power, can 

 be done more economically, and with less injury 

 to the road, at a low than a very high rate of 

 speed. It is, therefore, a very considerable object, 

 in rail-roads upon lines of public travel, to allow 

 wagons to pass others travelling in the same direc- 

 tion. Provision must be made, accordingly, for 

 turning out. This provision is particularly neces 

 sary in case of a road with a single set of tracks, 

 on which the carriages must meet. These turn- 

 outs are made by means of a movable or switch 

 rail at the angle where the turn-out track branches 

 from the main one. This rail is two or three feet, 

 more or less, in length, and one end may be moved 

 over that angle, and laid so as to form a part of 

 the main track, or the turn-out track. The switch 

 rail is usually moved by the hand, so as to form 

 a part of that track on which the wagon is to 

 move. 



Carriages. Wheels. The bodies of the wagons 

 will, obviously, require to be constructed with 

 reference to the kind of transportation. Tire prin- 

 cipal consideration, in regard to the construction of 

 the carnages, relates to their bearings on the axle 

 and the rim of the wheel. The rule given by Mr 

 Wood, as to the bearing on the axle, is, that in 

 order to produce the least friction, the breadth of 

 the bearing should be equal to the diameter of the 

 axle at the place of bearing. This diameter must 

 be determined by the weight to be carried ; and 

 the breadth of the bearing will accordingly vary 

 with it. The objection to the plate rail, as already 

 stated, is, that the breadth of the bearing of the rim 

 of the wheel upon such a rail, causes an unneces- 

 sary additional friction ; and the resistance to the 

 wheel is increased in consequence of the greater 

 liability of such a rail to collect dust and other 

 impediments upon its surface. The edge rail is 

 preferable, in these respects; but, at first, these 

 rails were liable to one difficulty, in consequence of 

 their wearing grooves in the rim of the wheel, so 

 that the friction was continually increasing, and 

 the wheel soon became unfit for use. To remedy 

 this defect, the rims were case-hardened, or chilled, 

 by rolling them, when hot, against a cold iron 

 cylinder. Wheels so case-hardened, are found to 

 be subject to very little wear. It was, at first, ob- 

 jected to the use of iron wheels, that they would 

 not take sufficiently strong hold of the rails to draw 

 any considerable load after them, and that therefore 

 they would not answer for the use of locomotive 

 engines. Where horses are Iht motive- power, it is 



