arging rate, for 8 hours should be,
as we have seen, one-eighth of the ampere-hour capacity of the
battery. Thus a "6-60" battery would require a 7-1/2 ampere current.

Connecting two such batteries in "series" (that is, the negative pole
of one battery to the positive pole of the second) would make a
12-volt battery. Ten or twelve such batteries could be connected in
"series," and a 110-volt direct current generator would charge them in
8 hours at a 7-1/2 ampere rate.

The diagram on page 259 shows the connections for charging on a
110-volt circuit.

An ordinary 16-candlepower carbon lamp is of 220 ohms resistance, and
(by Ohm's Law, C equals E divided by R) permits 1/2 ampere of current
to flow. By connecting 15 such lamps across the mains, in parallel,
the required 7-1/2 amperes of current would be flowing from the
generator through the lamps, and back again. Connect the battery in
"series" at any point on either of the two mains, between the lamps
and the generator, being careful to connect the positive end to the
positive pole of the battery, and _vice versa_.

Lamps are the cheapest form of resistance; but in case they are not
available, any other form of resistance can be used. Iron wire wound
in spirals can be used, or any of the many makes of special resistance
wire on the market. First it is necessary to determine the amount of
resistance required.

We have just seen that the charging rate of a 60-ampere hour battery
is 7-1/2 amperes. Applying Ohm's Law here, we find that ohms
resistance equals volts divided by amperes, or R = 110/7.5 = 14.67
ohms. With a 220-volt current, the ohms resistance required in series
with the storage battery of this size would be 29.33 ohms.

_Automobile Power for Lighting_

There are many ingenious ways by which an automobile may be utilized
to furnish electric light for the home. The simplest is to run wires
direct from the storage battery of the self-starting system, to the
house or barn, in such a way that the current may be used for reading
lamps in the sitting room. By a judicious use of the current in this
way, the normal operation of the automobile in the daytime will keep
the battery charged for use of the night lamps, and if care is used,
such a plan should not affect the life of the battery. Care should be
used also, in this regard, not to discharge the battery too low to
prevent its utilizing its function of starting the car when it was
desired to use the car.