right from the service box in the foreground. The conduits are of various types; creosoted wooden tubes are placed in creosoted wooden casings; wrought-iron pipes are sometimes laid in asphaltic concrete with creosoted wooden box; another arrangement is to be of composition blocks on concrete, and cover them with brick—or wrought-iron pipe is lined with cement, and laid in hydraulic cement concrete and cased with creosoted plank. About 85 per cent. of all the conduits have been constructed on this plan, the interior diameter of the pipes being 2½ inches. [Illustration: FIG. 30.] [Illustration: FIG. 31.] Fig. 31 shows how the street arc lighting wires are taken, also a branch for house use, out of the man-holes, which are placed at each street crossing. For the cleaning purposes and for drawing the cable through the conduits, these must be laid practically straight. [Illustration: FIG. 32.] Fig. 32 illustrates a method proposed by Mr. Kenneth Mackenzie, which is somewhat similar to the system of conduit which, used at Tours for the past two years, has been found most efficient for the high potential supply mains to the transformers. The troughs would be about 4 ft. long and 15 in. deep, having spigot and socket joints at the ends like ordinary water pipes. Transverse pieces of wood, or preferably slate, would rest upon projections, and would support the mains, and a cover recessed as shown would make the conduit fairly water-tight; drain holes would be provided, and the branches to houses led off through glands in the side of troughs. The American plan is, doubtless, the best, as there is no space for moisture to collect in the conduits; but Mr. Mackenzie’s system is well worth trying, and has the advantage of being much cheaper in first cost. The Edison plan is to place two solid conductors in a tube which is filled up solid with an insulating material, suitable bends and offsets being supplied, so that the tube containing the two conductors can be buried in the ground like a gas-pipe. The system is very largely used both in the United States and in Continental cities; but it is doubtful whether the protection would suffice in our towns, where the streets are already at the mercy of the gas and water companies, whose workmen, with a single blow of a pick, might perforate the tube, and cause a dangerous short circuit. THE INTERESTS OF GAS COMPANIES AS TO ELECTRIC LIGHTING.