is normally plentiful
during these months, the problem of power would be greatly simplified.
The heaviest draft on such a plant in summer would be during
harvesting; otherwise it would be confined to light, small power for
routine work, and cooking. Thus, a plant capable of meeting all the
ordinary requirements of the four dry months of summer, when water is
apt to be scarce, doubles or quadruples its capacity during the
winter months, to meet the necessities of heat for the house.

A dynamo requires only as much power to drive it, at any given time,
as is being used in terms of electricity. There is some small loss
through friction, of course, but aside from this the power required of
the prime mover (the water wheel) is always in proportion to the
amount of current flowing. When water is scarce, and the demands for
current for heating are low, it is good practice to close a portion of
the buckets of the turbine wheel with wooden blocks provided for this
purpose. It is necessary to keep the speed of the dynamo uniform under
all water conditions; and where there is a great fluctuation between
high and low water periods, it is frequently necessary to have a
separate set of pulleys for full gate and for half-gate. The head must
remain the same, under all conditions. Changing the gate is in effect
choking or opening the nozzle supplying the wheel, to cut down or
increase its consumption of water.

_The Average Plant_

It will be the exceptional plant, however, among the hundreds of
thousands to be had on our farms, which will banish not only the oil
lamp and kitchen stove, but all coal or wood burning stoves as
well--which will heat the house in below-zero weather, and provide
power for the heavier operations of the farm. Also, on the other hand,
it will be the exceptional plant whose capacity is limited to
furnishing a half-dozen lights and no more.

A happy medium between these two conditions is the plant large enough
to supply between five and ten electrical horsepower, in all seasons.
Such a plant will meet the needs of the average farm, outside of
winter heating and large power operations, and will provide an excess
on which to draw in emergencies, or to pass round to one's neighbors.
It is such a plant that we refer to when we say that (not counting
labor) its cost, under ordinary conditions should not greatly exceed
the price of one sound young horse for farm work.

Since the plant we described briefly in th