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It has been ſaid, that Iſland Cryftal ſhines in the Dark after it has been calcined in Manner of the Bolonian Stone; but this is not particular to that Species: It is the Quality of all Spar as Spar; only there requires great Nicety in the Calcination: Perhaps Selenite alſo has this Power. Linnæus refers the Bolonian Stone to Spars: To me it has appeared rather a Selenite; and of all Bodies in Nature, moſt of Kin to that Species of Selenite we call the Star, upon the waxen Vein. I have therefore retained it in that Place, till more of this ſcarce Foſſil comes in my Way for Trial: If it proves Spar, 'tis eaſily removed into that Claſs; and thus, and only thus, we can arrive at Truth; after a thouſand Errors.
That the Hog Spar affords Flowers on Sublimation, has been urged as a great Proof of its containing Salts of ſome Kind or other; known or unknown: But ſurely this Property is more naturally reſolved into another Source. All Bitumens yield Flowers on Sublimation; and we have the Teſtimony of our Senſes to the Preſence of a Bitumen in the Lapis Suillus: It ſtinks of it. Nay more, there is a Smell of Sulphur in all Spar, when calcined: Henkel and Wallerius, as well as I, have found it; and if we could give way to any Thought of Secondary Forms in a Foſſil whoſe Conſtruction appears perfectly homogene, and ſimple, my Senſe of it would be, not to ſeek them in imaginary Salts, but real Sulphur.
