RAILWAY PASSING PLACES, POINTS, AND CROSSINGS. In the railways first constructed in Britain, most of which were for private use in the mining districts, a single line of way formed the railway, the carriages getting off the main line when it was required that another train should pass, by means of what have been termed sidings, or passing places, namely, a branch diverging laterally from off the main line for a short distance, and then returning to it. In these railways the rule was for the loaded carriages to keep the main line, and the empty ones to cross to the siding till the others had passed. The point and switch rails, as may be seen on the older railways, were of most simple construction—a short piece of the rail turning on a pivot. Fig. 39. represents a crossing rail generally used on railways of this Fig. 39. description. From the obvious inconvenience and danger attending points and crossings, especially if the carriages went at any speed, various contrivances were made to pass without interruption, or the necessity of altering the moveable piece of rail called a switch, which required much atten tion. The plan adopted where the traffic in each direction was nearly equal, was to have crossings of the rails laid in such a way at particular places that, at these, both trains diverged a little to one side, forming a circuitous course till they passed each other, dispensing with the moveable switch. A plan of this kind is much used in underground railways. Another mode is to have a spring switch opening to the wheels of the carriages, and allowing them to go on. The great object in these contrivances was to avoid the necessity of manual labour. Fig. 40. represents one end of a passing place, for a single line of railway, by which carriages, proceeding in opposite directions, diverge equally from each other at the same time. This plan may be worked without the necessity of moving the switch by the hand. The point rail at the one angle, and corresponding one at the opposite place of divergence may remain always open by means of a powerful spiral spring, moving back the point to its original position, when the carriages have passed, the points of the opposite angles being always kept shut. By another arrangement of the spring a contrary action may be made to take place, for when the moveable rail is pushed to Fig. 40. wards the fixed rail by the wheels of the carriages the spring immediately closes it again. In other plans of crossings the passing-place simply diverges to one side of the main line, and returns to it again, the point opening to the retiring carriage, and returning by a spring to its former position. Mr. N. Wood describes a self-acting plan adopted at the Killingworth Colliery, where the loaded carriages keep by the main line and the empty ones diverge on one side, and return again when the former have passed; a spring switch being made to open to the wheels of the loaded carriages, and allowing them to proceed, while it makes the empty ones diverge to one side. The spiral spring is enclosed in an iron tube, and connected with the moveable rail, and by an arrangement of the spring it can be made to act against the rail, and be kept constantly shut, or the spring may be made to act the reverse way, and keep it open, and press it firmly against the fixed rail. These contrivances of springs to move the point rails from the sharpness of the bends and joltings at concussion, are not so well adapted for double lines. Indeed, in the latter case, crossing places are not so much required, as a train requires only occasionally to deviate into a passing place, and the more seldom the better for safety. The point rails on lines for locomotive engines are considered to be more safely worked by the hand; it has, therefore, been properly viewed as a matter both of prudence and of necessity, that railways constructed for quick speed should have a double line of way. A single line for such purposes has, with a few exceptions, therefore, been almost entirely done away with; and it is now a rare circumstance in this country even to find one proposed, notwithstanding the temptation to adopt single lines from their less expense; although, as has been previously stated, many of the lines in America, one of them said to be of great length, have merely a single line of way. In a double line of railway one of the lines is termed the up-line, and the other the downline, the up-carriages invariably keeping on the one line, and the down-carriages on the other. When a quick train has to pass a slow train, going in the same direction, the latter has to go off the main line to a siding-place, and places of this kind and crossings are provided at different points of the line, or at stations. At most of the termini of railways four lines are laid down with crossings; and turn-tables are provided for the facility of changing the carriages on the lines. Fig. 41. is the plan of a common crossing, running obliquely across a double line of rails. The angles are shown, more acute than they are in reality made, for sharp angles Fig. 41. could not be worked with safety on rail ways, owing to the great shock in passing, creating a liability to throw the wheels off the rails. The angle of railway crossings for great speed should not be more than from 2 to 21 degrees, but for slow speed the angle is commonly 6 to 7 degrees. At the points of intersection of the rails grooves are provided for the flanches of the wheels, and guard rails are placed within the line, to keep the inside flanch from getting off the rails. So important for railway safety is the setting of the switches, as the least neglect may occasion the most serious accidents, that some railways have a signal apparatus affixed to them, which indicates to the driver of the train as he approaches the exact position of the switch. The method in use of moving the crossing points on railways is much the same as that first adopted on the Liverpool and Manchester line. Two cast-iron plates about 9 feet in length are fixed on the blocks or sleepers, and have a |