ever formed any Subſtance that could be properly ſo called; all that I have been ſhewn as ſuch, having been Things which a little Chemiſtry was able to ſhew that Naturaliſts ought to have been aſhamed of calling by ſuch a Name: Not that I would pretend to limit the Operations of Nature within the Bounds of our narrow Underſtandings; or declare any Thing impoſſible, becauſe it has not yet been ſeen to be effected: But I think the Aſſertors of ſuch great Effects from ſo very uncertain a Subſtance, ought, if ever they had ſeen it, to have given a more rational Account of it than any we have at preſent.
The Zaffer we know, and with which the blue Glaſs and counterfeit Sapphires are ſtained, is a Preparation which ſeems to owe its preſent Mode of Exiſtence to the extreme Force of Fire; and is perhaps no genuine Production of Nature, even in a latent State, except in its conſtituent Principles. It is prepared from Cobalt, affording, by the Aſſiſtance of Fire, the Arſenics, this Subſtance; and Smalt, with the Addition of a fixed Alkali. After the Fire of a reverberatory Furnace has driven off the arſenical Particles, the remaining Maſs is powdered and calcined three or four Times over; and then being mixed with three Times its Quantity of powdered Flints, affords us the common Zaffer.
But it may be proper to examine what Weight, even allowing the Exiſtence of a na-
tive
