or other voltages.

There are two general exceptions to this rule as to 110-volt plants:
(1) If the plant is located at a distance greater than a quarter of a
mile from the house, it will be found cheaper (in cost of transmission
line, as will be shown later) to adopt the 220-volt plant; (2), If the
water supply is so meagre that it must be stored for many hours at a
time, and then used for charging storage batteries, it will be found
most economical to use a 30-volt plant. A storage battery is made up
of cells of approximately 2 volts each; and, since more than 55 such
cells would be required for a 110-volt installation, its cost would
be prohibitive, with many farmers.

So we will assume that this plant is a 110-volt plant, to be run
without storage battery. It will be well to make a chart, dividing the
farm requirements into three heads--light, heat, and power.

_Light_

[Illustration: 60 and 100 watt Mazda tungsten lamp. These lamps may be
had in sizes from 10 to 500 watts (1/4 scale)]

[Illustration: The lamp of the future. A 1000 watt Mazda nitrogen
lamp, giving 2000 candlepower (1/4 scale)]

Light is obtained by means of incandescent lamps. There are two styles
in common use, the carbon and the tungsten lamp. It requires 3.5 to 4
watts of electricity to produce one candlepower in a carbon lamp. It
requires from 1 to 1.25 watt to produce one candlepower in the
tungsten lamp. The new nitrogen lamp, not yet in general use, requires
only 1/2 watt to the candlepower. Since tungsten lamps give three
times the light of the carbon lamp, they are the most economical to
use in the city or town where one is paying for commercial current.
But, in the country where water-power furnishes current for nothing,
it will be found most economical to use the carbon lamp, since its
cost at retail is 16 cents, as compared with 30 cents for a
corresponding size in tungsten. A 60 watt carbon lamp, of 16
candlepower; or a 25 watt tungsten lamp, of 20 candlepower, are the
sizes to use. In hanging lamps, as over the dining room table, a 100
watt tungsten lamp, costing 70 cents, and giving 92 candlepower light
is very desirable; and for lighting the barn-yard, these 100 watt
tungsten lamps should be used. For reading lamps, the tungsten style,
of 40 or 60 watt capacity, will be found best. Otherwise, in all
locations use the cheaper carbon lamp. Both styles have a rated life
of 1,000 hours, after which they begin to fall off in effi