This sleeper presents very great stiffness, at the same time preserving its lightness; and the feature which specially distinguishes this railway from others of the same class is not only its extreme strength, but above all its solidity, which results from its bearing equally upon the ground by means of the rail base and of the sleepers.
In special cases, M. Decauville provides also railroads with projecting sleepers, whether of flat steel beaten out and rounded, or of channel iron; but the sleeper and the rail are always inseparable, so as not to lessen the strength, and also to facilitate the laying of the line. If the ground is too soft, the railway is supported by bowl sleepers of dished steel, Figs. 3 and 4, especially at the curves; but the necessity for using these is but seldom experienced. The sleepers are riveted cold. The rivets are of soft steel, and the pressure with which this riveting is effected is so intense that the sleepers cannot be separated from the rails, even after cutting off both heads of the rivets, unless by heavy blows of the hammer, the rivets being driven so thoroughly into the holes made in the rails and sleepers that they fill them up completely.
The jointing of the rails is excessively simple. The rail to the right hand is furnished with two fish-plates; that to the left with a small steel plate riveted underneath the rail and projecting 1¼ in. beyond it. It is only necessary to lay the lengths end to end with one another, making the rail which is furnished with the small plate lie between the two fish-plates, and the junction can at once be effected by fish-bolts. A single fish-bolt, passing through the holes in the fish-plates, and through an oval hole in the rail end, is sufficient for the purpose.
With this description of railway it does not matter whether the curves are to the right or to the left. The pair of rails are curved to a suitable radius, and can only need turning end for end to form a curve in the direction required. The rails weigh 9 lb., 14 lb., 19 lb., and 24 lb. per running yard, and are very similar to the rails used on the main railways of France, except that their base has a proportionally greater width. As to the strength of the rail, it is much greater in proportion to the load than would at first sight be thought; all narrow-gauge railways being formed on the principle of distributing the load over a large number of axles, and so reducing the amount on each wheel. For instance, the 9 lb. rail used for the portable railway easily bears a weight of half a ton for each pair of wheels.
The distance between the rails differs according to the purpose for which they are intended. The most usual gauges are 16in., 20 in., and 24in. The line of 16 in. gauge, with 9 lb. rails, although extremely light, is used very successfully in farming, and in the interior of workshops.
Fig. 3. Fig. 4. Fig. 5.
A length of 16 ft. 5 in. of 9 lb. steel rail, to 16 in. gauge, with sleepers, etc., scarcely weighs more than 1 cwt., and may therefore be readily carried by a man placing himself in the middle and taking a rail in each hand.
Those members of the Institution who recently visited the new port of Antwerp will recollect having seen there the portable railway which Messrs. Couvreux and Hersetit had in use; and as it was these works at the port of Antwerp that gave rise to the idea of this paper, it will be well to begin with a description of this style of contractor's plant.
The earth in such works may be shifted by hand, horsepower, or locomotive. For small works the railway of 16 in. gauge, with the 9 lb. rails, is commonly used, and the trucks carry double equilibrium tipping-boxes, containing 9 to 11 cubic feet. These wagons, having tipping-boxes without any mechanical appliances, are very serviceable; since the box, having neither door nor hinge, is not liable to need repairs.