SPECIAL RAILWAY SYSTEMS.
the day of the locomotive, inclined planes operated by cables or bands were nsed for raising or lowering loaded wagons npon steep inclines. When the load was to be lowered, it was sufficient that it should have enough overweight to raise the empty wagons up the slope by gravity, the speed regulation being effected partly by lasting the ascending train (with water, for example) and partly by a suit able brake. In this case the cable or band was passed over a drum at the summit of the incline. When the load was to be lifted up the slope instead of being- lowered, an endless cable or band was employed, which passed over drums located at the top and bottom of the incline. A sta tionary steam-engine at the summit was used to set the upper drum in rotation. The loaded wagons to be drawn up the slope were attached to the cable by various devices (hooks, pushers, etc.), and were also provided with suitable brakes, and occasionally, in addition to these, with certain automatic safety appliances. The greater number of the inclines formerly operated by stationary engines and cables are llOW abandoned, the con struction of more powerful locomotives having made it possible to dispense with them. Several inclines in connection with steam-railways operated by cables and stationary engines are in nse in France, Belgium, and Ger many. In the United States similar plans on an extensive scale, in con nection with city railway-lines, are in use, notably in Cincinnati Go/. 34, fig. 4), Pittsburgh, and elsewhere.
Incline with Stationaly modification of this cable system has been proposed by an Italian engineer (Agudio), and tried successfully on a section of the Turin-Genoa railway. The stationary engine at the summit is dispensed with, and the cable, which is stationary, plays a role analogous to that of the cables in the so-called " Belgian canal-towing-" system. In other words, a motor-car provided with several rotary pulleys draws itself and the train attached to it np the slope by gripping the cable. Other modifications of this plan will be mentioned in connection with passenger railways in cities (tramways).
The "Switchback" the anthracite coal-regions of Penn sylvania the so-called "switchback " system, used in connection with the inclined planes just described, was introduced over forty years ago, and is still largely employed. By this system the coal-cars are lowered from the stimmit by gravity, the steep g-radieut of the mountain-side being avoided by constructing a series of zigzag lines of comparatively gentle incline, along which the cars run backward and forward. The plan was first intro duced to lower coal-cars into the Nesquelioning \Talley, and soon came into general -use in the coal-region of Pennsylvania. It offers a very simple solution of a troublesome engineering problem. It will be understood that the cars come to a full stop at the end of every piece of line composing this zigzag system, so that the danger of their getting beyond the control of the brakes is thereby avoided. This system has been introduced by American engineers with success on the Callao, Lima and Aroya (now Transandine) Railroad, in Pern, in many respects the most remarkable specimen of rail way engineering in the world. Until quite recently it was also employed on the Cascade division of the Northern Pacific Railroad as a temporary expedient to cross the " Stampede Pass " while a tunnel (since completed) 9S5o feet in length was being driven throug,11 the mountain.
The "Big notable example of the methods for overcoming the difficulties of a steep ascent by a series of curves is illustrated by the so-called " Big Loop" (fii. 34,fig. r) on the Georgetown branch of the Union Pacific Railroad, in Colorado, between Georgetown and the mining camp of Silver Plume. The actual linear distance up the valley in this case is one and a quarter miles and the vertical distance of the ascent is 600 feet, to overcome which would require, with a straight line, a gradient of 4So feet to the mile. To obviate this, the line of the railroad was con structed in spiral form, with the result that, while it became necessary to increase the length of the line to four miles, the gradient was thereby reduced to 13o feet to the mile.