nne 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 {40} 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 _Musaeum 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 crystalliz