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 of the deepet Male Sapphires, and deeper than the commonly called black Veins of the rough native Turquoies, if carefully examined.

The Authors of this Objection might, indeed, have known, from the excellent Mr. Boyle's Experiments, that Copper is the lat Thing to be, with any hew of Reaon, upected of wanting this Property; for that Gentleman has proved, that a Grain of that Metal is capable of giving a blue Colour to 530,620 Times its Bulk of Water.

In regard to the Third Argument, That the genuine Sapphires are probably coloured by Zaffer, becaue blue Glas, and the counterfeit Sapphires are o; I cannot but oberve, that external Appearances are of little Weight in Philoophy; and I am orry to ay, that it was only a very uperficial View of thee Things, that could tart an Objection to Copper's colouring the Sapphire, from them: For a more careful Examination of thee very Bodies, mut afford Arguments for the contrary, as it will evidently prove, that the Colour of the Sapphire cannot be owing to the ame Subtance with that of thee Glaes: Since the very Heat neceary for forming them, would, in a few Minutes, wholly divet the finet Sapphire in the World of all its Colour.

The common blue Glas is made from the common or crytal Frit melted with Zaffer; and the finet counterfeit Sapphires, with a crytal Glas, worked with an Admixture of Lead, and this Zaffer, in the Proportion of about