In the Fossils Arranged of "Sir" John Hill (Lond., 1771), p. 123, is the following entry: "Black crystal. Small very hard heavy glossy. Perfectly black, opake. Bristol (grottos, glass)" referring to its use.
The name Vincentina is not known as occurring in any mineralogical book. Prof. H. A. Miers, F.R.S., writes concerning the passage: "Anglica gemma sive fluor seems to be a synonym for Bristolla, or possibly for Vincentina et Bristolla. Both quartz and fluor are found at Clifton. In that case Vincentina and Bristolla refer to these two minerals, and if so one would expect Bristolla to be the Bristol Diamond, and Vincentina to be the comparatively rare Fluor spar from that locality."
At the end of the edition of 1653 of Sir Hugh Plat's Jewel House of Art and Nature, is appended A rare and excellent Discourse of Minerals, Stones, Gums, and Rosins; with the vertues and use thereof, By D. B. Gent. Here, p. 218, we read:
"We have in England a stone or mineral called a Bristol stone (because
many are found thereabouts) which much resembles the Adamant or Diamond, which is brought out of Arabia and Cyprus; but as it is wanting of the same hardnesse, so falls it short of the like vertues."
[121] Page 48, line 18. Page 48, line 19. Crystallus.—Rock-crystal. Quartz. Pliny's account of it (Philemon Holland's version of 1601, p. 604) in book xxxvii., chap, ii., is:
"As touching Crystall, it proceedeth of a contrarie cause, namely of cold; for a liquor it is congealed by extreame frost in manner of yce; and for proofe hereof, you shall find crystall in no place els but where the winter snow is frozen hard: so as we may boldly say, it is verie yce and nothing else, whereupon the Greeks have give it the right name Crystallos, i. Yce.... Thus much I dare my selfe avouch, that crystall groweth within certaine rockes upon the Alps, and these so steepe and inaccessible, that for the most part they are constrained to hang by ropes that shall get it forth."
[122] Page 48, line 18. Page 48, line 20. Similes etiam attrahendi vires habere videntur vitrum ... sulphur, mastix, & cera dura sigillaris. If, as shown above, the electric powers of diamond and ruby had already been observed, yet Gilbert was the first beyond question to extend the list of electrics beyond the class of precious stones, and his discovery that glass, sulphur, and sealing-wax acted, when rubbed, like amber, was of capital importance. Though he did not pursue the discovery into mechanical contrivances, he left the means of that extension to his followers. To Otto von Guericke we owe the application of sulphur to make the first electrical machine out of a revolving globe; to Sir Isaac Newton the suggestion of glass as affording a more mechanical construction.
Electrical attraction by natural products other than amber after they have been rubbed must have been observed by the primitive races of mankind. Indeed Humboldt in his Cosmos (Lond., 1860, vol. i., p. 182) records a striking instance:
"I observed with astonishment, on the woody banks of the Orinoco, in the sports of the natives, that the excitement of electricity by friction was known to these savage races, who occupy the very lowest place in the scale of humanity. Children may be seen to rub the dry, flat and shining seeds or husks of a trailing plant (probably a Negretia) until they are able to attract threads of cotton and pieces of bamboo cane."