On heavy railroads worked by electricity the overhead conductor is replaced by a third rail along the middle of the track, and insulated from the ground In another system the middle conductor is buried underground, and the current is tapped at intervals by the motor connecting with it for a moment by means of spring contacts as the car travels In each case, however, the outer rails serve as the return conductors Another system puts one or both the conductors in a conduit underground, the trolley pole entering through a narrow slot similar to that used on cable roads The first electric carriages for ordinary roads were constructed in 1889 by Mr. Magnus Volk of Brighton. Figure 78 represents one of these made for the Sultan of Turkey, and propelled by a one- horse-power Immisch electric motor, geared to one of the hind wheels by means of a chain. The current for the motor was supplied by thirty "EPS" accumulators stowed in the body of the vehicle, and of sufficient power to give a speed of ten miles an hour. The driver steers with a hand lever as shown, and controls the speed by a switch in front of him. Vans, bath chairs, and tricycles are also driven by electric motors, but the weight of the battery is a drawback to their use. In or about the year 1839, Jacobi sailed an electric boat on the Neva, with the help of an electromagnetic engine of one horse- power, fed by the current from a battery of Grove cells, and in 1882 a screw launch, carrying several passengers, and propelled by an electric motor of three horse-power, worked by forty-five accumulators, was tried on the Thames. Being silent and smokeless in its action, the electric boat soon came into favour, and there is now quite a flotilla on the river, with power stations for charging the accumulators at various points along the banks. Figure 79 illustrates the interior of a handsome electric launch, the Lady Cooper, built for the "E P S," or Electric Power Storage Company. An electric motor in the after part of the hull is coupled directly to the shaft of the screw propeller, and fed by "E P S" accumulators in teak boxes lodged under the deck amidships. The screw is controlled by a switch, and the rudder by an ordinary helm. The cabin is seven feet long, and lighted by electric lamps. Alarm signals are given by an electric gong, and a search-light can be brought into operation whenever it is desirable. The speed attained by the Lady Cooper is from ten to fifteen knots. M. Goubet, a Frenchman, has constructed a submarine boat for discharging torpedoes and exploring the sea bottom, which is propelled by a screw and an electric motor fed by accumulators. It can travel entirely under water, below the agitation of the waves, where sea-sickness is impossible, and the inventor hopes that vessels of the kind will yet carry passengers across the Channel.