of the deepeſt Male Sapphires, and deeper than the commonly called black Veins of the rough native Turquoiſes, if carefully examined.
The Authors of this Objection might, indeed, have known, from the excellent Mr. Boyle's Experiments, that Copper is the laſt Thing to be, with any ſhew of Reaſon, ſuſpected 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, becauſe blue Glaſs, and the counterfeit Sapphires are ſo; I cannot but obſerve, that external Appearances are of little Weight in Philoſophy; and I am ſorry to ſay, that it was only a very ſuperficial View of theſe Things, that could ſtart an Objection to Copper's colouring the Sapphire, from them: For a more careful Examination of theſe very Bodies, muſt afford Arguments for the contrary, as it will evidently prove, that the Colour of the Sapphire cannot be owing to the ſame Subſtance with that of theſe Glaſſes: Since the very Heat neceſſary for forming them, would, in a few Minutes, wholly diveſt the fineſt Sapphire in the World of all its Colour.
The common blue Glaſs is made from the common or cryſtal Frit melted with Zaffer; and the fineſt counterfeit Sapphires, with a cryſtal Glaſs, worked with an Admixture of Lead, and this Zaffer, in the Proportion of
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