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'All this, added to the delightfulness of the autumn day and the horrible Causse of Sauveterre, but just passed, transformed the dreary town and narrow valley of Florac into a delicious retreat. In a note he gives the accepted derivation of Causse from calx, saying that it was of general application, and that the word certainly filled a blank in French nomenclature.

Thus Silver and Tin separately dissolv'd in Aqua Fortis, will the one Præcipitate it self, and the other be Præcipitated by common Salt-water into a White Calx, and so will Crude Lead and Quicksilver first dissolv'd likewise in Aqua Fortis.

The like Calx will be afforded as I have try'd by a Solution of that shining Mineral Tinglass dissolv'd in Aqua Fortis, and Præcipitated out of it; and divers of these Calces may be made at least as Fair and White, if not better Colour'd, if instead of Oyl of Tartar they were Præcipitated with Oyl of Vitriol, or with another Liquor I could Name.

Of this you may remember, that I have given you several Instances already, to which may be added such as these, That if Quicksilver be dissolv'd in Aqua fortis, and Præcipitated out of the Solution, either with water impregnated with Sea salt, or with the spirit of that Concrete, it falls to the Bottom in the form of a white powder, whereas if it be Præcipitated with an Alcaly, it will afford a Yellowish or tawny powder, and if there be no Præcipitation made, and the Menstruum be drawn off with a convenient fire, the corroded Mercury will remain in the bottom, in the form of a substance that may be made to appear of differing Colours by differing degrees of Heat; As I remember that lately having purposely abstracted Aqua fortis from some Quicksilver that we had dissolv'd in it, so that there remain'd a white Calx, exposing that to several degrees of Fire, and afterwards to a naked one, we obtain'd some new Colours, and at length the greatest part of the Calx lying at the Bottome of the Vial, and being brought partly to a Deep Yellow, and partly to a Red Colour, the rest appear'd elevated to the upper part and neck of the Vial, some in the form of a Reddish, and some of an Ash-Colour Sublimate.

The results were these: there was no change in the total weight of the apparatus and its contents; when the vessel was opened after the calcination was finished, air rushed in, and the whole apparatus now weighed more than it did before the vessel was opened; the weight of the air which rushed in was exactly equal to the increase in the weight of the tin produced by the calcination, in other words, the weight of the inrushing air was exactly equal to the difference between the weights of the tin and the calx formed by calcining the tin.

In his Elements of Chemistry he made use of this new nomenclature, and it seemed so clearly an improvement over the old that the scientific world hastened to adopt it. In this connection Lavoisier says: "We have, therefore, laid aside the expression metallic calx altogether, and have substituted in its place the word oxide.

Upon the borders of the parish stands Aston-furnace, appropriated for melting ironstone, and reducing it into pigs: this has the appearance of great antiquity. From the melted ore, in this subterranean region of infernal aspect, is produced a calx, or cinder, of which there is an enormous mountain.

For we have try'd, that though by Evaporating a Solution of Quick-Silver in Aqua-fortis, and abstracting the Liquor till the remaining matter began to be well, but not too strongly dryed, fair Water pour'd on the remaining Calx made it but somewhat Yellowish; yet when we took good Quick-Silver, and three or four times its weight of Oyl of Vitriol, in case we in a Glass Retort plac'd in Sand drew off the Saline Menstruum from the Metalline Liquor, till there remain'd a dry Calx at the bottome, though this Precipitate were a Snow White Body, yet upon pouring on it a large quantity of fair Water, we did almost in a moment perceive it to pass from a Milky Colour to one of the loveliest Light Yellows that ever we had beheld.

Tin also, that wants not, according to the Chymists, a Sulphur Joviale, when throughly burned by the fire into a Calx, is not Black, but eminently White. And I lately noted to you out of Bellonius, that the Charcoals of Oxy-cedar are not of the former of these two Colours, but of the latter.

Still further, on continuing the investigation, it may be shown that the oxide or calx, as it used to be called, has become heavier by combining with one of the ingredients of the air.