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foſſile Kingdom certain remarkable Earths, dug out of Pits, the Formation[1] of which, as was obſerved in the beginning of this Treatiſe (owing either to the mere Afflux or Percolation of their conſtituent Parts) is from a more pure and equal Matter than the other more common Kinds. And theſe re-
- ↑ The various Operations of Nature, in the Formation of theſe and other foſſile Subſtances, have been treated of at large in the Beginning of this Work; the greateſt of all Diſtinctions among them, is that of ſuch as are found in the perpendicular Fiſſures, and ſuch as are depoſited in Strata. The Difference between theſe Kinds, in their Degree of Purity and Fineneſs, is extremely great, and muſt neceſſarily be ſo, from their different Manner of Formation; as thoſe of the perpendicular Fiſſures have been formed by Percolation, at different Times; and thoſe of Strata, by mere Subſidence from among the Waters of the general Deluge.
and when pure and unmixed, keeps conſtantly its fluid Form. It may be amalgamed with all other metallic Subſtances, but is moſt difficultly made to mix with Antimony, Iron, and Copper. It penetrates the Subſtance of all Metals, and diſſolves, and makes them brittle. It is the heavieſt of the Metals except Gold, which is to it as 4 to 3, or thereabout; and therefore will not ſwim in it, as all other Metals do. It is, however, notwithſtanding its Weight, extremely volatile, and eaſily raiſed in Form of a very ſubtle Vapour; and in that Form is diſſipated entirely by means of Fire.
Quickſilver, from its ill Effects on the Miners and People employed about large Quantities of it, was long eſteemed a Poiſon the Antients. Dioſcorides reckons it a Thing which muſt have very pernicious Effects in Medicine; and Galen believed it highly corroſive. It firſt got into Uſe externally among the Arabians; and afterwards, but not till long afterwards, was introduced into the Number of internal Medicines, from the repeated Obſervations of its Safety and good Effects when given to Cattle, and from the hardy Attempts of ſome unhappy People, who had ventured. to take it down in large Quantities (in order to procure Abortion) but without any Effect.
