Page:Popular Science Monthly Volume 59.djvu/351

Rh rubs and brings near his versorium glass, sulphur, opal, diamond, sapphire, carbuncle, rock-crystal, sealing-wax, alum, resin, etc., and he finds that all these attract his suspended needle, and not only the needle, but everything else. His words are remarkable: 'Ad electrica feruntur omnia.' Here is a great advance on the amber and jet, the only two bodies previously known as having the power to attract 'straws, chaff and twigs,' the usual test-substances of the ancients. Pursuing his investigations, he finds a class of bodies which perplex him, because when nibbed they do not affect his electroscope. Among these he enumerates: bone, ivory, marble, flint, silver, copper, gold, iron, even the lodestone itself. The former class he called electrica, electrics, deriving the term from electron, the Greek name for amber; the latter class he termed anelectrica, non-electrics.

Science therefore owes to Gilbert the terms electric and electrical; the term electricity was a coinage of a later period, due probably to the illustrious Irish philosopher, Robert Boyle, who uses the term in his work On the Mechanical Production of Electricity, published in 1675. Gilbert never uses electricitas, but speaks of corpora electrica, effluvia electrica, attractio electrica, motus electricus and the like. Had Gilbert chosen the Latin name for amber, succinum, as he might have done, we should not be speaking to-day of electricity, electrostatics, electro-optics, electrics, dielectrics; but should probably be using succinic for electric, succinical for electrical, succinicity for electricity, together with a series of harsh-sounding derivatives and compounds.

As we said, Gilbert was perplexed by the anomalous behavior of his anelectrics. He toiled and labored hard to find out the cause. He undertook a long, abstract, philosophical discussion of the nature of bodies which, from its very subtlety, failed to reveal the cause of his perplexing anomaly. Gilbert failed to discover the distinction between conductors and insulators, and, as a consequence, never found out that similarly electrified bodies repel each other. Had he but suspended an excited stick of sealing-wax, what a promised land of electrical wonders would have unfolded itself to his vision! and what a harvest of results such a reaper would have gathered in! He noticed the effect of distance; for he says, 'The nearer the electric is to the versorium, the quicker is the attraction.' It was reserved, however, for the French mathematician and engineer, Coulomb, to show in 1785 that the law of attraction or repulsion between two electrified particles varies inversely as the square of the distance between them.

From solids, he proceeds to examine the behavior of some liquids, and finds that they too are susceptible of electrical influence. He notices that a piece of excited amber when brought near a drop of water