ure constant speed.

_The Standard Voltage Set_

In response to a general demand, the first type (the direct-connected
standard voltage set) has been developed to a high state of efficiency
recently, and is to be had in a great variety of sizes (ranging from
one-quarter kilowatt to 25 kilowatts and over) from many
manufacturers.

The principle of the gasoline engine as motive power is so familiar to
the average farmer that it needs but a brief description here.
Gasoline or other fuel (oil, gas, or alcohol) is transformed into
vapor, mixed with air in correct proportions, and drawn into the
engine cylinder and there exploded by means of a properly-timed
electric spark.

Internal combustion engines are of two general types--four-cycle and
two-cycle. The former is by far the more common. In a four-cycle
engine the piston must travel twice up and down in each cylinder, to
deliver one power stroke. This results in one power impulse in each
cylinder every two revolutions of the crank shaft. On its first down
stroke, the piston sucks in gas. On its first up stroke, it compresses
the gas. At the height of this stroke, the gas is exploded by means of
the electric spark and the piston is driven down, on its power stroke.
The fourth stroke is called the scavening stroke, and expels the
burned gas. This completes the cycle.

A one-cylinder engine of the ordinary four-cycle type has one power
stroke for every two revolutions of the fly wheel. A two-cylinder
engine has one power stroke for one revolution of the fly wheel; and a
four-cylinder engine has two power strokes to each revolution. The
greater the number of cylinders, the more even the flow of power. In
automobiles six cylinders are common, and in the last year or two,
eight-cylinder engines began appearing on the market in large numbers.
A twelve-cylinder engine is the prospect for the immediate future.

Since the dynamo that is to supply electric current direct to lamps
requires a steady flow of power, the single-cylinder gas or gasoline
engine of the four-cycle type is not satisfactory as a rule. The
lights will flicker with every other revolution of the fly wheel. This
would be of no importance if the current was being used to charge a
storage battery--and right here lies the reason why a cheaper engine
may be used in connection with a storage battery than when the dynamo
supplies the current direct for lighting.

A two-cylinder engine is more even in its flow