cted continuously, is
the hot water boiler, and this can be credited with at least one
electrical horsepower 24 hours a day. It is a small contrivance, not
much bigger than a quart can, attached to the back of the kitchen
boiler, and it keeps the water hot throughout the house at all hours.
Its cost will vary with the make, ranging from $8 to $15; and since it
is one of the real blessings of the farm kitchen and bathroom, it
should be included in all installations where power permits. Electric
radiators will be used 24 hours a day in winter, and not at all in
summer. They are portable, and can be moved from room to room, and
only such rooms as are in actual use need be heated. The other devices
are for intermittent service, many of them (like the iron) for only a
few hours each week.

The grill, chafing dish, coffee percolator, etc., which are used on
the dining room table while the family is at meals, each draw an
equivalent of from 6 to 10 carbon lights. By keeping this in view and
turning off spare lights, one can have the use of them, with even a
small plant. Thus, a one kilowatt plant permits the use of any one of
these lamp circuit devices at a time, with a few lights in addition.

_Power_

Electric power is to be had through motors. A direct current dynamo
and a direct current motor are identical in construction. That is, a
motor becomes a generator if belted to power; and a generator becomes
a motor, if connected to electric mains. This is best illustrated by
citing the instance of a trans-continental railroad which crosses the
Bitter Root Mountains by means of electric power. Running 200 miles up
a 2 per cent grade, it is drawn by its motors. Coasting 200 miles
down the 2 per cent grade on the other side of the mountains, its
motors become generators. They act as brakes, and at the same time
they pump the power of the coasting weight of this train back into the
wires to help a train coming up the other side of the mountains.

[Illustration: Connections of shunt motor and starting rheostat]

Just as there are three types of direct current generators, so there
are three types of direct current motors: _series_, _shunt_, and
_compound_, with features already explained in the case of generators.
Motors are rated by horsepower, and generators are rated by kilowatts.
Thus a one kilowatt generator has a capacity of 1,000 watts; as a
motor, it would be rated as 1000/746 horsepower, or 1.34 horsepower.
Their eff