the battery, connecting one wire to the carbon and one to the
zinc, and connecting both to the zinc. Then he decided that
one wire was all that had to be connected anyway, that the
second was simply to make it stronger. Which of the ways he
tried, if any, would have been right?

[Illustration: FIG. 125. Parallel circuits.]

[Illustration: FIG. 126. How should he connect them?]

_APPLICATION 53._ Dorothy was moving. "When they took out our
telephone," she said to her chum, Helen, "the electrician just
cut the wires right off."

"He must have turned off the electricity first," Helen
answered, "or else it would all have run out of the cut ends
of the wire and gone to waste."

"Why, it couldn't," Dorothy said. "Electricity won't flow off
into the air."

"Of course it can if there is nothing to hold it in," Helen
argued.

Which was right?

INFERENCE EXERCISE

Explain the following:

321. It is very easy to get chilled when one is perspiring.

322. Ice cream becomes liquid if you leave it in your dish too
long.

323. You should face forward when alighting from a street car.

324. There are always at least two electric wires going into a
building that is wired.

325. Woolen sweaters keep you warm.

326. Steel rails are not riveted to railroad ties but the
spikes are driven close to each rail so that the heads hook
over the edge and hold the rail down without absolutely
preventing its movement forward and backward. Why should rails
be laid in this way?

327. The earth keeps whirling around the sun without falling
into it, although the pull from the sun is very great.

328. Electricity is brought down from power houses in the
mountains by means of cables.

329. White clothes are cooler than black when the person
wearing them is out in the sun.

330. All the street cars along one line are stopped when a
trolley wire breaks.

SECTION 36. _Grounded circuits._

Why can a bird sit on a live wire without getting a shock,
while a man would get a shock if he reached up and took hold
of the same wire?

We have just been laying emphasis on the fact that for electricity to
flow out of a dynamo or battery, it must have a complete circuit back
to the battery or dynamo. Yet only one wire is needed in order to
telegraph between two stations. Likewise, a