[Illustration: A switchboard and its connections: _G._ Dynamo; _A._ Shunt field coils; _B._ Series coils; _DD._ Fuses; _FF._ Main switch; _F._ Field switch; _C._ Ammeter; _V._ Voltmeter; _E._ Lamp; _R._ Rheostat. Dotted lines show connections on back of board] _Items of Cost_ This water wheel would cost $250 new. There is a duplicate in the neighborhood bought at second-hand, for $125. The dynamo cost $90, and was picked up second-hand in New York City. New it would cost $150. The voltmeter cost $7, and the ammeter $10; and the switches and fuses could be had for $5. A wheel one-half the size, using one-half the amount of water at full gate, would do the work required, and the cost would be correspondingly less. _Capacity_ This plant supplies two farms with electric light. One farm (that of the owner of the wheel) has 30 lamps, of 16 candlepower each, and two barn-yard lamps of 92 candlepower each. His wife has an electric iron and an electric water heater. Needless to say, all these lamps, and the iron and water heater are not in use at one time. [Illustration: Carbon Lamps Gem Type (1/4 scale)] The partner who owns the electric part of the plant has 30 lamps in his house and barn, many of them being 25 watt tungsten, which give more light for less power, but cost more to buy. They are not all in use at one time, though (since the current costs nothing) the inclination is to turn them on at night and let them burn. In his kitchen he has an electric range, and a water heater for the 40 gallon boiler. In addition to this he has all sorts of appliances,--irons, toasters, grills, a vacuum cleaner, a vibrator, etc. Naturally all these appliances are not in use at one time, else the draft on the plant would be such as to "blow" the fuses. For instance, all the baking is done in daylight; and when the oven is used after dark, they are careful to turn off all lights not needed. An ideal plant, of course, would be a plant big enough to take care of the sum of lamps and handy devices used at one time. To make this plant ideal, (for, being an actual affair, it has developed some short-comings, with the extension of the use of electricity) it would require a dynamo whose capacity can be figured, from the following: