repairs.

_Gas and Gasoline Engines_

In gas engines power is derived from the explosion of a mixture of gas
and air. Where a gas supply is available, such engines are very
convenient, for, once started, they will run for hours without
attention. They are economical in the consumption of gas, and give
trouble only where the quality of gas varies.

Owing to the unavailability of gas on the farm and in country houses,
two other forms of pumping engines have been devised which are
becoming exceedingly popular. One is the gasoline, the other is the
oil engine. Both resemble the gas engine, but differ from it in using
a liquid fuel which is volatilized by a sprayer. Gasoline engines are
now brought to a high state of perfection.

_Kerosene or Crude Oil as Fuel_

In recent years, internal-combustion engines which use heavy kerosene
or crude oil as fuel have been introduced. These have two palpable
advantages: first, they are safer than gasoline engines; second, they
cost less to run, for crude oil and even refined kerosene are much
cheaper than gasoline. Oil engines resemble the gas and gasoline
engines, but they have larger cylinders, because the mean effective
pressure evolved from the explosion is much less than that of the
gasoline engines.

Oil engines for pumping water are particularly suitable in regions
where coal and wood cannot be obtained except at exorbitant cost.
Usually, the engine is so built as to be adapted for other farm work.
It shares this advantage with the gasoline engine. Oil engines are
simple, reliable, almost automatic, compact, and reasonable in first
cost and in cost of repairs. There are many forms of such engines in
the market. To be successful from a commercial point of view, an oil
engine should be so designed and built that any unskilled attendant
can run, adjust, and clean it. The cost of operating them, at eight
cents per gallon for kerosene, is only one cent per hour per
horse-power; or one-half of this when ordinary crude oil is used. The
only attention required when running is periodical lubrication and
occasional replenishing of the oil reservoir. The noise of the
exhaust, common to all engines using an explosive force, can be
largely done away with by using a muffler or a silencer. The smell of
oil from the exhaust likewise forms an objection, but can be overcome
by the use of an exhaust washer.

_Steam and Electric Pumps_

The well-known forms of steam-pumping engines