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narrow strips of the' thinnest tissue paper, or, better still,
two strips of gold leaf, are hung from a support in a wide-
mouthed glass bottle which serves at once to insulate and
protect the strips from draughts of air.

The mouth of the jar is closed by a plug of parafin wax,
through the center of which passes a small glass tube. A
stifl copper wire passes through the tube. The lower end of
the wire is bent at right angles to furnish support for the
strips of gold leaf. A round sheet metal disk about the size
of a quarter is soldered to the upper end of the rod.

If an electrified stick of sealing-wax or a glass rod is pre-
sented to the disk of the electroscope, the strips will repel
each other very strongly. If the instrument is sensitive,
the strips should begin to diverge some time before the rod
reaches the disk. It is possible to make an electroscope so
sensitive that chips formed by sharpening a pencil will
cause the strips to diverge.

There are two kinds of static electricity. Rub a glass
rod with a piece of silk and then suspend it in a wire stirrup
as shown in Figure 25. Excite a
second rod also with a piece of
silk and bring it near one end of
the suspended one. The suspended
rod is repelled and will swing away
from the one held in the hand.
FIG.25._MethodofSuspend_ Now rub a stick of sealing-wax

ing an Electrified Rod in a with a piece of flannel until the

Wire Stirrup“ sealing-wax is electrified. Then



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