When a fixed line is used, it is better to replace the movable switch by a fixed cast-iron switch, and to let the workmen who drive the wagon push it in the direction required. Planed switch tongues are also used, having the shape of those employed on the normal tracks, especially for the passage of small engines; the switches are, in this case, completed by the application of a hand lever.
The portable turntable consists of two faced plates laid over the other, one of thick sheet iron, and the other of cast iron. The sheet-iron plate is fitted with a pivot, around which the cast iron one is made to revolve; these plates may either be smooth, or grooved for the wheels. The former are used chiefly when it is required to turn wagons or trucks of light burden, or, in the case of earthworks, for trucks of moderate weight. These plates are quite portable; their weight for the 16 in. gauge does not exceed 200 lb. For engineering works a turntable plate with variable width of track has been designed, admitting of different tracks being used over the same turntable.
When turntables are required for permanent lines, and to sustain heavy burdens, turntables with a cast iron box are required, constructed on the principle of the turntables of ordinary railways. The heaviest wagons may be placed on these box turntables, without any portion suffering damage or disturbing the level of the ground. In the case of coal mines, paper mills, cow houses with permanent lines, etc., fixed plates are employed. Such plates need only be applied where the line is always wet, or in workshops where the use of turntables is not of frequent occurrence. This fixed plate is most useful in farmers' stables, as it does not present any projection which might hurt the feet of the cattle, and is easy to clean.
The only accident that can happen to the track is the breaking of a fish-plate. It happens often that the fish-plates get twisted, owing to rough handling on the part of the workmen, and break in the act of being straightened. In order to facilitate as much as possible the repairs in such cases, the fish-plates are not riveted by machinery, but by hand; and it is only necessary to cut the rivets with which the fish-plate is fastened, and remove it if broken: A drill passed through the two holes of the rail removes all burrs that may be in the way of the new rivet. No vises are required for this operation; the track to be repaired is held by two workmen at a height of about 28 in. above the ground, care being taken to let the end under repair rest on a portable anvil, which is supplied with the necessary appliances. The two fish-plates are put in their place at the same time, the second rivet being held in place with one finger, while the first is being riveted with a hammer; if it is not kept in its place in this manner it may be impossible to put it in afterward, as the blows of the hammer often cause the fish-plate to shift, and the holes in the rail are pierced with great precision to prevent there being too much clearance. No other accident need be feared with this line, and the breakage described above can easily be repaired in a few minutes without requiring any skilled workman.
The narrow-gauge system, which has recently received so great a development on the Continent, since its usefulness has been demonstrated, and the facility with which it can be applied to the most varied purposes, has not yet met in England with the same universal acceptance; and those members of this Institution who crossed the sea to go to Belgium were, perhaps, surprised to see so large a number of portable railways employed for agricultural and building purposes and for contractors' works. But in the hands of so practical a people it may be expected that the portable narrow gauge railway will soon be applied even to a larger number of purposes than is the case elsewhere.
GERARD'S ALTERNATING CURRENT MACHINE.
The machine represented in the annexed engravings consists of a movable inductor, whose alternate poles pass in front of an armature composed of a double number of oblong and flat bobbins, that are affixed to a circle firmly connected with the frame. There is a similar circle on each side of the inductor. The armature is stationary, and the wires that start from the bobbins are connected with terminals placed upon a wooden support that surmounts the machine.
