The needs of the railway contractor have called for such locomotives, for which several systems of power have been tried. In many ways the electric locomotive has distinct advantages over its rivals, steam and compressed air, for these narrow gage lines. Reviewing these advantages briefly, we see that the electrical equipment is more economical to work, as one good stationary engine develops power much more cheaply than several small locomotives. Again, the electric locomotive can be more readily designed for narrow gages than steam or compressed air locomotives. [Illustration: FIG. 1--AN ELECTRIC LINE EQUIPPED ON THE KOPPEL SYSTEM.] [Illustration: FIG. 2.--THE SECTION WITH THE SUPPORT FOR THE OVERHEAD LINE.] A new system of equipment of such lines is now being introduced into this country by Mr. Arthur Koppel, of 96 Leadenhall Street, E. C. The keynote of this system is flexibility, the arrangements being such that extensions or alterations can be readily effected. In fact, the line is portable, and it is claimed also to be cheaper than the ordinary construction. The overhead conductor is employed, as can be seen from Fig. 1, which gives a general view of a locomotive and train of skips on a line actually at work abroad. The supports for the wire are not provided by separate posts and brackets in the usual way, but by arched carriers attached to the sections of railway line, thereby forming a portable section of the electric railway, as illustrated by Fig. 2. The steel carrier or "arch" is fixed to one of the sleepers, which is made of sufficient length for that purpose. On the straight line these line supports are placed about 25 yards apart. In curves of a small radius each section of tramway is provided with an arch, to keep the line of the wire as nearly as possible parallel to the curve of the line. Apart from these special extended sleepers with wire carriers attached, the line is constructed in the ordinary mariner with rails 14 lb. per yard and upward. As the electric locomotives are lighter than steam locomotives, the weight of rail required is somewhat less. The special trolley for erecting the wires along the railway line is shown in Fig. 3. This consists of an ordinary four wheeled platform wagon with ladder, and wire drum with tightening gear and clamps or grips for anchoring the trolley to the line. The wire is led over a sheave on top of the ladder and fixed to the picket post at the beginning of the line. When erecting the wire the trolley is pushed beyond the first carrier arch, clamped on to the rails, and the wire is then tightened by means of the tightening gear. It is then firmly fixed to the insulator on the carrier arch The tension in the copper wire is taken up by a second portable ladder, which is also provided with a tightening gear and can be clamped to the rails in the same manner as the trolley, so that the trolley can then be pushed behind the second carrier arch and the process previously described repeated.