Such installations are not expensive. A storage battery capable of lighting 8 tungsten lamps, of 16 candlepower each, continuously for 8 hours (or fewer lamps for a longer time); a switchboard containing all the required regulating instruments; and a dynamo of suitable size, can be had for from $250 to $300. All that is necessary to put such a plant in operation, is to belt the dynamo to the gasoline engine so that it will run at proper speed; and to connect the wires from dynamo to switchboard, and thence to the house service. The dynamo required for the above plant delivers 10 amperes at 45 volts pressure, or 10 × 45 = 450 watts. A gasoline, gas, or oil engine, or a windmill of 1-1/2 horsepower furnishes all the power needed. If the farmer uses his engine daily, or every other day, for other purposes, the cost of power will be practically negligible. With this system electric lights are available at any time day or night; and when the gasoline engine is in service daily for routine farm chores, the battery will never run low. This system is especially desirable where one uses a windmill for power. The speed of the windmill is constantly fluctuating, so much so in fact that it could not be used for electric light without a storage battery. But when equipped with a regulator on the switchboard which permits the current to flow only when the battery needs it, and then only when the speed of the windmill is correct, the problem of turning wind power into electric light is solved. * * * * *