(6.) Diamond. In spite of the confusion already noted, à propos of adamas (Note to p. [47]), between loadstone and diamond, there seems to be one distinct record of an attractive effect having been observed with a rubbed diamond. This was recorded by Fracastorio, De sympathia et antipathia rerum (Giunta edition, Venice, MDLXXIIII, chap. v., p. 60 verso), "cujus rei & illud esse signum potest, cum confricata quædã vt Succinum, & Adamas fortius furculos trahunt." And (on p. 62 recto); "nam si per similitudine (vt supra diximus) fit hæc attractio, cur magnes non potius magnetem trahit, q˜ ferrum, & ferrum non potius ad ferrum movetur, quàm ad magnetem? quæ nam affinitas est pilorum, & furculorum cum Electro, & Adamante? præsertim q˜ si cum Electro affines sunt, quomodo & cum Adamante affinitatem habebunt, qui dissimilis Electro est?" An incontestable case of the observation of the electrification of the diamond occurs in Gartias ab Horto. The first edition of his Historia dei Semplici Aromati was publisht at Goa in India in 1563. In chapter xlviii. on the Diamond, occur these words (p. 200 of the Venetian edition of 1616): "Questo si bene ho sperimentato io più volte, che due Diamanti perfetti fregati insieme, si vniscono di modo insieme, che non di leggiero li potrai separare. Et ho parimente veduto il Diamante dopo di esser ben riscaldato, tirare à se le festuche, non men, che si faccia l'elettro." See also Aldrovandi, Musæum Metallicum (Bonon., 1648, p. 947).
Levinus Lemnius also mentions the Diamond along with amber. See his Occulta naturæ miracula (English edition, London, 1658, p. 199).
[119] Page 48, line 16. Page 48, line 18. Iris gemma.—The name iris was given, there can be little doubt, to clear six sided prisms of rock-crystal (quartz), which, when held in the sun's beams, cast a crude spectrum of the colours of the rainbow. The following is the account of it given in Pliny, book xxxvii., chap. vii. (p. 623 of the English version of 1601):
"... there is a stone in name called Iris: digged out of the ground it is in a certaine Island of the red sea, distant from the city Berenice three score miles. For the most part it resembleth Crystall: which is the reason that some hath tearmed it the root of Crystall. But the cause why they call it Iris, is, That if the beames of the Sunne strike upon it directly within house, it doth send from it against the walls that bee neare, the very resemblance both in forme and also in colour of a rainebow; and eftsoones it will chaunge the same in much varietie, to the great admiration of them that behold it. For certain it is knowne, that six angles it hath in manner of the Crystall: but they say that some of them have their sides rugged, and the same
unequally angled: which if they be laid abroad against the Sunne in the open aire, do scatter the beames of the Sunne, which light upon them too and fro: also that others doe yeeld a brightnes from themselves, and thereby illuminat all that is about them. As for the diverse colours which they cast forth, it never happeneth but in a darke or shaddowie place: whereby a man may know, that the varietie of colours is not in the stone Iris, but commeth by the reverberation of the wals. But the best Iris is that which representeth the greatest circles upon the wall, and those which bee likest unto rainebowes indeed."
In the English translation of Solinus's De Mirabilibus (The excellent and pleasant worke of Julius Solinus containing the noble actions of humaine creatures, the secretes and providence of nature, the descriptions of countries ... tr. by A. Golding, gent., Lond., 1587), chapter xv. on Arabia has the following:
"Hee findeth likewise the Iris in the Red sea, sixe cornered as the Crystall: which beeing touched with the Sunnebeames, casteth out of him a bryght reflexion of the ayre like the Raynebowe."
Iris is also mentioned by Albertus Magnus (De mineralibus, Venet., 1542, p. 189), by Marbodeus Gallus (De lapidibus, Par. 1531, p. 78), who describes it as "crystallo simulem sexangulam," by Lomatius (Artes of curious Paintinge, Haydocke's translation, Lond., 1598, p. 157), who says, "... the Sunne, which casting his beames vpon the stone Iris, causeth the raine-bowe to appeare therein ...," and by "Sir" John Hill (A General Natural History, Lond., 1748, p. 179).
Figures of the Iris given by Aldrovandi in the Musæum Metallicum clearly depict crystals of quartz.
[120] Page 48, line 16. Page 48, line 18. Vincentina, & Bristolla (Anglica gemma siue fluor). This is doubtless the same substance as the Gemma Vincentij rupis mentioned on p. 54, line 16 (p. [54], line 18, of English Version), and is nothing else than the so-called "Bristol diamond," a variety of dark quartz crystallized in small brilliant crystals upon a basis of hæmatite. To the work by Dr. Thomas Venner (Lond., 1650), entitled Via Recta or the Bathes of Bathe, there is added an appendix, A Censure concerning the water of Saint Vincents Rocks neer Bristol (Urbs pulchra et Emporium celebre), in which, at p. 376, occurs this passage: "This Water of Saint Vincents Rock is of a very pure, cleare, crystalline substance, answering to those crystalline Diamonds and transparent stones that are plentifully found in those Clifts."