RAILROADS or RAILWAYS. Roads constructed of tracks of iron called rails, on which the wheels of carriages roll, and to which they are confined by ledges or flanges raised either on the rail or on the tires of the wheels.
History of Railways. About the mid dle of the 17th century, the transport of coals from the pits to the harbor was ef fected in the coal districts of Northum berland and Durham by laying down pa rallel tracks of timber with a horse-path between them, the wheels being confined upon the beams or rails of timber by ledges or flanges projecting from the in side of the tire of the wheels. These timber rails were constructed in pieces of about six feet long with a section of about four inches square ; they were sup ported on pieces of timber called sleepers laid at right angles to them transversely on the road. These sleepers were laid. at about two feet apart, so that each pair of parallel rails was supported by three sleepers ; besides giving support to the rails, these sleepers also had the effict of maintaining the rails in gauge, or in keep ing them at a fixed distance asunder. The rails were fastened to the sleepers by pins driven quite through the rails, and half way through the sleepers ; to pre serve the uniformity of the upper sur face of the rail; these wooden pins were planed off at the top.
The necessity of giving room for the flanges of the wheels, running as they did below the surface of the rail, and the small depth between the surface of the rail and the sleeper, rendered it impossi ble to protect the sleepers effectually from the action of the horses' feet by any co vering of gravel or other material. The sleepers were consequently subject to be worn and destroyed. The rails, also, being worn by the action of the wheels still more rapidly than the sleepers, re quired to be frequently replaced ; and, each new rail being pinned down to the same sleeper, the ends of the sleepers were gradually perforated by so many holes that the sleepers were weakened, and required to be soon replaced. These defects were remedied by the adoption of the double timber railway, which con sisted in laying upon the surface of the timber rails, above described; additional rails of timber of equal scantling, at tached to the lower rails by wooden pins, passing quite through the upper and half through the lower rails, in the same man ner as the lower rails themselves were at tached to the transverse sleepers. This change was attended with many advan tages. Besides the increased strength given to the rails by the double timbers, the depth of the sleepers below the up per surface of the superior rail, allowed the sleepers to be protected from the ac tion of the horses feet by covering them with broken stones, gravel, or other road materials. The structure of rails and sleepers also being stronger and more weighty, and held down by the road ma terial with which the sleepers were co vered, allowed a packing or ballasting to be driven under the rails, so as to give greater stability and firmness to the road.
Another advantage obtained by this ar rangement was, that when the superior rails were worn by the action of the wheels, they could be replaced by new ones without disturbing the inferior rails ; and as the places of the joints, and those at which they were attached by pins to the inferior rails, could be varied atplea sure, the pin-holes made in the inferior rails would not come in the same place, or near each other, so as injuriously to weaken the latter.
The next improvement consisted in the addition of a plate or bar of iron, about two inches broad and half an inch thick, laid aloag, the, upper surface of the supe rior rail, and attached to it by nails or iron pins countersunk in it. The wheels of the carriages ran upon this iron rail, which formed a more durable surface than that of the wood. In our country railways of this construction are still in very general use. They are recommended by the abundance and cheapness of tim ber, and the comparative high cost of iron. Such a road is tolerably efficient where the traffic is light, and can there fore be resorted to in localities and cir cumstances in which an adequate return could not be obtained for the capital ne cessary for the construction of these tim ber railways. On this continent many other improvements have been intro duced, more especially in the substruc ture of the road. In laying out the road way for the reception of the rails, two parallel trenches are cut along the line of way corresponding to the distance be tween the rails, and transverse trenches at right angles to these are cut to receive the sleepers : these trenches are respec tively bottomed with a ballasting of bro ken stone, on which the rails and cross sleepers rest. This basis answers the double purpose of a firm and durable support for the road and an effectual means of drainage. The mantling of the timbers used for the rails is usually six inches in width by ten inches in .depth : they are attached to the sleepers, so as to be at once kept from springing from them and from altering their gauge, by the following means : A notch is cut in the sleeper corresponding to the size and form of the rail ; and the rail, at the place where it is let into the sleeper, is formed with a vertical surface on the outside, and a levelled surface on the inside, increasing in width downwards. When let into the notch of the sleeper, the levelled part of the rail is forced into the corresponding cavity of the notch by a wedge driven between the outside edge of the rail and the outer surface of the notch.