"I advise you to put on your canvas gloves while you work; then you
can't get a shock," added another member of the family.

"That's a good idea," said the wife, "but wet the gloves, then you
will have the double protection of the water and the cloth."

The man laughed and went to work on the socket. He did not get a
shock. Which advice, if any, do you think he followed?

INFERENCE EXERCISE

Explain the following:

311. A red postage stamp looks greenish gray in the green
light of a mercury-vapor lamp.

312. Cracks are left between sections of the roadbed in cement
auto highways.

313. Electricity goes up a mountain through a wire.

314. It is impossible to stand sidewise against a wall on one
foot, when that foot touches the wall.

315. A charged storage battery will run an electric
automobile.

316. An empty house is noisier to walk in and talk in than is
a furnished one.

317. Lightning rods are made of metal.

318. It is harder to hold a frying pan by the end of the
handle than by part of the handle close to the pan.

319. Diamonds flash many colors.

320. In swimming, if you have hold of a fastened rope and try
to pull it toward you, you go toward it.

SECTION 35. _Complete circuits._

Why does a doorbell ring when you push a button?

Why is it that when you touch one electric wire you feel no
shock, while if you touch two wires you sometimes get a shock?

When a wire is broken in an electric light, why does it not
light?

Suppose you have some water in an open circular trough like the one
shown in Figure 123. Then suppose you have a paddle and keep pushing
the water to your right from one point. The water you push pushes
the water next to it, that pushes the water next to it, and so on all
around the trough until the water just behind your paddle pushes in
toward the paddle; the water goes around and around the trough in
a complete circuit. There never is too much water in one place; you
never run out of water. But then suppose a partition is put across the
trough somewhere along the circuit. When the water reaches that, it
cannot pass; it has no place to flow to, and the current of water
stops.

THE ELECTRIC CIRCUIT. The flow of electricity in an electric circuit
may be compared to the flow of the water in the tank we have been
imagining. The long loop of wire extending