At the very outset, he found it necessary to invent a recording instrument to test the electrification produced by rubbing a great variety of substances. This he appropriately called a _versorium_; we would call it an electroscope. "Make to yourself," he says, "a rotating needle of any sort of metal three or four fingers long and pretty light and poised on a sharp point." He then briskly rubs and brings near his versorium glass, sulphur, opal, diamond, sapphire, carbuncle, rock-crystal, sealing-wax, alum, resin, etc., and finds that all these attract his suspended needle, and not only the needle, but everything else. His words are remarkable: "All things are drawn to electrics." 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 numerous bodies which perplex him, because when rubbed 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; the latter was termed _anelectrica_, non-electrics. To Gilbert we, therefore, are indebted for the terms electric and electrical, which he took from the Greek name for amber instead of succinic and succinical, their Latin equivalents. The noun electricity was a coinage of a later period, due probably to Sir Thomas Browne, in whose _Pseudodoxia Epidemica_, 1646, it occurs in the singular number on page 51 and in the plural on page 79. It may interest the reader to be here retold that we owe the chemical term _affinity_ to Albertus Magnus, _barometer_ to Boyle, _gas_ to van Helmont, _magnetism_ to Barlowe, magnetic _inclination_ to Bond, electric _circuit_ to Watson, electric _potential_ to Green, _galvanometer_ to Cumming, _electro-magnetism_ to Kircher, _electromagnet_ to Sturgeon, and _telephone_ to Wheatstone.