Shellac.
Rough glass.

NEGATIVE (-).

The list shows that quality, as well as kind, of material affects
the production of electricity. Thus polished glass when rubbed
with silk is positive, whereas rough glass is negative. Cork at
ordinary temperature is positive when rubbed with hot cork. Black
silk is negative to white silk, and it has been observed that the
best radiator and absorber of light and heat is the most negative.
Black cloth, for instance, is a better radiator than white, hence
in the Arctic regions, where the body is much warmer than the
surrounding air, many wild animals get a white coat in winter, and
in the tropics, where the sunshine is hotter than the body, the
European dons a white suit.

The experiments of figures 1, 2, and 3 have also shown us that
when the pithball is charged with the positive electricity of the
glass rod it is REPELLED by the like charge upon the rod, and
ATTRACTED by the negative or unlike charge on the handkerchief.
Again, when it is charged with the negative electricity of the
handkerchief it is REPELLED by the like charge on the handkerchief
and ATTRACTED by the positive or unlike charge on the rod.
Therefore it is usual to say that LIKE ELECTRICITIES REPEL AND
UNLIKE ELECTRICITIES ATTRACT EACH OTHER.

We have said that all bodies yield electricity under the friction
of dissimilar bodies; but this cannot be proved for every body by
simply holding it in one hand and rubbing it with the excitor, as