=Hauling by Way of Entrances.=--When the hauling is done by the way of the entrances, the materials to be hauled are taken directly from the point of construction to the entrances, or in the opposite direction, by means of special cars of different patterns. For general purposes, these different patterns of cars may be grouped into three classes,--platform-cars, dump-cars, and box-cars. Representative examples of these several classes of cars are shown in Figs. 33 to 36[6] inclusive, but it will be readily understood that there are many other forms. [6] Reproduced from catalogue of Arthur Koppel, New York. Briefly described, platform-cars (Fig. 33) consist of a wooden platform mounted on tracks, and they are usually employed for the transportation of timber, ties, etc. Dump-cars are used in greater numbers in tunnel work than any other form. Fig. 34 shows a dump-car of metal construction, and Fig. 35 one constructed with a metal under-frame and wooden box. These cars are made to run on narrow-gauge tracks, and usually have a capacity of about one to one and one-half cubic yards. Box-cars are more extensively employed in Europe for tunnel work than in America. Fig. 36 shows a typical European box-car for tunnel work. It is made either to run on narrow-gauge or standard-gauge tracks. [Illustration: FIG. 34.--Iron Dump-Car for Tunnel Work.] [Illustration: FIG. 35.--Wooden Dump-Car for Tunnel Work.] [Illustration: FIG. 36.--Box-Car for Tunnel Work.] It is usually desirable in tunnel work to employ cars of different forms for different parts of the work. In rock tunnels it is a common practice to use narrow-gauge cars of small size in the headings, and larger, broad-gauge cars for the enlargement of the profile. Where narrow-gauge cars are employed for all purposes, it will also be found more convenient to use platform-cars for handling the construction material, and dump-cars for removing the spoil. The extent to which it is desirable to use cars of different forms will depend upon the character and conditions of the work, and particularly upon how far it is possible to install the permanent track.