lts, and the secondary has 50 turns of
wire, the secondary will give forth only one-half as much as the
primary, or 100 volts.

If, on the other hand, 400 volts would be required, the secondary should
have 200 turns in the winding.

VOLTAGE AND AMPERAGE IN TRANSFORMERS.--It must not be understood that,
by increasing the voltage in this way, we are getting that much more
electricity. If the primary coil, with 100 turns, produces a current of
200 volts and 50 amperes, which would be 200 x 50 = 10,000 watts, and
the secondary coil has 50 turns, we shall have 100 volts and 100
amperes: 100 (V.) x 100 (A.) = 10,000 watts. Or, if, on the other hand,
our secondary winding is composed of 200 turns, we shall have 400 volts
and 25 amperes, 400 (volts) x 25 (amperes) also gives 10,000 watts.

Necessarily, there will be some loss, but the foregoing is offered as
the theoretical basis of calculation.

CHAPTER XVI

ELECTRIC LIGHTING

The most important step in the electric field, after the dynamo had been
brought to a fairly workable condition, was its utilization to make
light. It was long known prior to the discovery of practical electric
dynamos, that the electric current would produce an intense heat.

Ordinary fuels under certain favorable conditions will produce a
temperature of 4,500 degrees of heat; but by means of the electric arc,
as high as six, eight and ten thousand degrees are available.

The fact that when a conductor, in an electric current, is severed, a
spark will follow the drawing part of the broken ends, led many
scientists to believe, even before the dynamo was in a practical shape,
that electricity, sooner or later, would be employed as the great
lighting agent.

When the dynamo finally reached a stage in development where its
operation could be depended on, and was made reversible, the first
active steps were taken to not only produce, but to maintain an arc
between two electrodes.

It would be difficult and tedious to follow out the first experiments
in detail, and it might, also, be useless, as information, in view of
the present knowledge of the science. A few steps in the course of the
development are, however, necessary to a complete understanding of the
subject.

Reference has been made in a previous chapter to what is called the
_Electric Arc_, produced by slightly separated conductors, across which
the electric current jumps, producing the brilliantly lighted area.

This light i