ght is turned
off, the engine stops automatically.

Since the installation of a direct-connected standard voltage plant of
this type is similar in every respect, except as to motive power, to
the hydro-electric plant, its cost, with this single exception, is the
same. The same lamps, wire, and devices are used.

With gasoline power, the cost of the engine offsets the cost of the
water wheel. The engine is more expensive than the ordinary gasoline
engine; but even this item of cost is offset by the cost of labor and
materials used in installing a water wheel.

The expense of maintenance is limited to gasoline and oil.
Depreciation enters in both cases; and though it may be more rapid
with a gasoline engine than a water wheel, that item will not be
considered here. The cost of lubricating oil is inconsiderable. It
will require, when operated at from one-half load to full load,
approximately one pint of gasoline to each horsepower hour. When
operated at less than half-load, its efficiency lowers. Thus, for a
quarter-load, an average engine of this type may require three pints
of gasoline for each horsepower hour. For this reason it is well, in
installing such a plant, to have it of such size that it will be
operating on at least three-fourths load under normal draft of
current. Norman H. Schneider, in his book "Low Voltage Electric
Lighting," gives the following table of proportions between the engine
and dynamo:

Actual watts Actual Horsepower Nearest engine size
150 .5 1/2
225 .7 3/4
300 .86 1
450 1.12 1-1/4
600 1.5 1-1/2
750 1.7 1-3/4
1000 2.3 2-1/2
2000 4.5 5
4000 9.0 10

This table is figured for an efficiency of only 40 per cent for the
smaller generators, and 60 per cent for the larger. In machines from 5
to 25 kilowatts, the efficiency will run considerably higher.

To determine the expense of operating a one-kilowatt gasoline
generator set of this type, as to gasoline consumption, we can assume
at full load that the gasoline engine is delivering 2-1/2 horsepower,
and consuming, let us say, 1-1/4 pint of gasoline for each horsepower
hour (to make allowance f