'I have often enquired, amongst our London Drugsters, for Egyptian Nitre, and if I had been so fortunate as to have found any, I doubt not but I should have been able to have put an end to that Question by a Demonstration; that is, by turning the greatest part of it into Salt-peter. However, the Observations I have made in my own private Experiments, and in the practice of Salt-peter-men and Refiners of Salt-peter, seem to give me sufficient ground to suspect, that the confidence of those, who hold them to be several Salts, proceedeth chiefly from their being unacquainted with the various Φαινόμενα of Salt-peter in the marking and refining of it: and also their comparing double refined Salt-peter (of which Gunpowder is made) with that description of Nitrum and Aphronitrum in the tenth chapter of the one and thirtieth Book of Pliny's Natural History (the only tolerable account of that Salt that hath been handed to us from Antiquity) where he tells us, That Aphronitrum was Colore pene purpureo, and Egyptian Nitre Fuscum & Lapidosum, adding afterward, Sunt ibi Nitrariæ in quibus rufum exit a colore terræ, which is sufficient to have hinted to any one but moderately versed in the moderate way of ordering Salt-peter, that the Antients were not at all skilled in refining their Nitre from the Earth and common Salt that is usually mingled with it, nor from that foul yellow Oyl, which, it seems, did accompany their Nitre, as well as it doth our Salt-peter, in great abundance; for Pliny takes notice of it, when he mentions the removing the Nitre (after it is grained) out of the Nitrariæ, saying, Hic quoque natura olei intervenit, ad scabiem animalium utilis: And
