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 rates upon it. And the Fumes of Lead have been observed sometimes (for I have not found the Effect to succeed always) to arrest the fluidity of Mercury, which change is supposed to be the effect of a Potential Coldness belonging to the Chymists Saturn in reference to fluid Mercury, though it have not that operation on any other liquor that we know of.

And lastly, (for I would not be too prolix) though Nitre and Sal Armoniac be both apart and joyntly Cold in reference to Water, and though, however Nitre be throughly melted in a Crucible, it will not take fire of it self, yet if, whilst it is in Fusion, you shall by degrees cast on it some powder'd Sal Armoniac, it will take fire and flash vehemently, almost as if Sulphur had been injected.