H—Magnetic and Electric Influences.
" electricity" is derived from the Greek " elektron," which was the
name for amber, a mineralised resin of extinct pine-trees. It was
well-known to the people of pro-historic times; later to the early
Egyptians, and, at a still later date, we have recorded how Thales— the
Greek philosopher, who lived about the close of the 7th Century B.C.,
and was one of the "seven wise men" —discovered the peculiar property
which we call " electricity " by rubbing dry silk on amber.
stones are capable of exhibiting the same phenomenon, not only by
friction, as in Thales's experiment, but also under the influence of
light, heat, magnetism, chemical action, pressure, etc., and of holding
or retaining this induced or added power for a long or short period,
according to conditions and environment.
a small pith ball is suspended from a non-conducting support, it forms
a simple and ready means of testing the electricity in a stone.
According to whether the ball is repelled or attracted, so is the
electricity in the stone made evident, though the electroscope gives
the better results. By either of these methods it will be found that
some of the stones are more capable of giving and receiv-