e the time because we are
charging with only one-half the voltage used in the first case.

The positive pole of the dynamo should be connected with the positive
pole of the accumulator cell, and negative with negative. When this has
been done run up the machine until it slightly exceeds the voltage of
the cells. Thus, if we have 50 cells in parallel, like in Fig. 64, at
least 125 volts will be required, and the excess necessary should bring
up the voltage in the dynamo to 135 or 140 volts.

[Illustration: _Fig. 65._ PARALLEL SERIES]

[Illustration: _Fig. 66._ CHARGING CIRCUIT]

THE INITIAL CHARGE.--It is usual initially to charge the battery from
periods ranging from 36 to 40 hours, and to let it stand for 12 or 15
hours, after which to re-charge, until the positive plates have turned
to a chocolate color, and the negative plates to a slate or gray color,
and both plates give off large bubbles of gas.

In charging, the temperature of the electrolyte should not exceed 100 deg.
Fahrenheit.

When using the accumulators they should never be fully discharged.

THE CHARGING CIRCUIT.--The diagram (Fig. 66) shows how a charging
circuit is formed. The lamps are connected up in parallel, as
illustrated. Each 16-candle-power 105-volt lamp will carry 1/2 ampere,
so that, supposing we have a dynamo which gives 110 volts, and we want
to charge a 4-volt accumulator, there will be 5-volt surplus to go to
the accumulator. If, for instance, you want the cell to have a charge of
2 amperes, four of these lamps should be connected up in parallel. If 3
amperes are required, use 6 lamps, and so on.

CHAPTER IX

THE TELEGRAPH

The telegraph is a very simple instrument. The key is nothing more or
less than a switch which turns the current on and off alternately.

The signals sent over the wires are simply the audible sounds made by
the armature, as it moves to and from the magnets.

MECHANISM IN TELEGRAPH CIRCUITS.--A telegraph circuit requires three
pieces of mechanism at each station, namely, a key used by the sender, a
sounder for the receiver, and a battery.

THE SENDING KEY.--The base of the sending instrument is six inches long,
four inches wide, and three-quarters of an inch thick, made of wood, or
any suitable non-conducting material. The key (A) is a piece of brass
three-eighths by one-half inch in thickness and six inches long. Midway
between its ends is a cross hole, to receive the pivot pin (B), which
also pa