are almost as ponderous as Metals themfelves: fuch are a great many Species of Spaad.

308. However, I would not have the fpecifick Gravity, nor the Figure be altogether overlooked, but rather made ufe of with the other Characterifticks; though no conftant and accurate Judgment can always be drawn from thefe alone.

309. But our Defign being to lay down the Principles of the Art of Affaying; it will be neceffary only, to mention the Characteristicks and distinguishing Marks of compound Minerals, as they are the moft frequent Objects of the faid Art (§ 2), and to fhew their conftituent Parts, as far as they make themselves known, together with the Difpofition of the whole Body with feveral Men@rua. It is likewise evident, that we cannot here mention all Ores without Exception, but that we must only chufe thofe that are less compound, or thofe at leaft which are more frequently met with.

310. We fhall refer every compound Mineral to the Class of that Simple, of which it contains the greatest Part in itfelf; except however Stones, and fimple Earths: for if the Claffes of these were to be determined from their predominant Parts; the Number of the Ores to be referred to that Clafs would be by much the greatest.

Scholion. For Inftance, let us fuppofe, that there are in a Lump, fix Parts of Copper, and one of Sulphur, a very Small Quantity of Arfenick, and twenty Parts of Quartz or Flint-ftone; we shall clafs this compound Body with the Copper-kind, and so on.

311. But we fhall call a Mineral proper to that Simple, which makes the greatest Part of it (§ 310), and improper to thofe which it contains in lefs Quantity: However, they are contained in it in fuch Manner, that they indeed enter into the Mixture of it, and must always accompany it wherever fuch Mineral is found. Finally, we fhall call it accidental to thofe Simples, which enter not into the Mixture of it, being only adherent to the Out-fide: Wherefore, they

may

may be or not be found with the Mineral now mentioned, and yet this Mineral remain ftill the famė.

Scholion. Let us clear this Matter by the foregoing Example (Schol. $310). The Mineral fuppofed there, containing Copper in the greatest Part, is called proper to Copper. But fo long as Sulphur and Arfenick are mixt together with the Copper, and render it of a particular Species, this Mineral, on account of the small Quantity of its fulphureous and arsenical Parts, is faid to be improper to them. Finally, the Stones or other Bodies, placed about er among that Mineral, are called accidental to it, as they are no conflituent Parts thereof, and it might fubfift without them.

Of Sulphur and fulphureous Minerals.

312. Mineral Sulphur, or common Brimstone, when free of all foreign Mixtures, is of a fold, friable. Confiftence; yellow, made up of large Maffes, and more or lefs half-transparent; it burns, makes a bluish Flame, with a fuffocating acid Vapour (§ 22), and thus is entirely confumed: Being put upon a gentle Fire, and in clofe Veffels, it melts without taking Fire; and, when melted, changes its Colour into a bright Red: it no fooner grows cold again, but it refumes its Solidity and yellow Colour. It is compofed of the pureft inflammable Principle (§ 24), and of a much greater Quantity of Acid of Vitriol (§ 22): on which Account it finks in Water, being much heavier than pure Oil. The Chemical Analyfis, and the Production by Art of true Sulphur, out of the two Principles juft mentioned, confirm what has been faid of it.

313. In this State (§ 312.) native Sulphur is digged out of the Earth; though not fo very frequently: it is likewife brought in fuch a State by Waters, which on this Account are called particularly medicinal, and it applies itself to the Walls of the Springs.

314. It is frequently found mixt with fimple Earths and Stones; varying its Dye, and being fometimes

white,

white, fometimes grey, yellow, or of other Colours, belonging to the Bodies mixt with it.

315. Whenever Sulphur is tinctured with a dark, or bright Orange or red Colour, this always betrays Arfenick in it: Wherefore, Sulphurs thus coloured are not true, nor very valuable.

316. The most frequent and almoft the proper Mineral of Sulphur is the Pyrites flavus, or yellow Pyrites. This, when free of all heterogeneous Matters at the outside, and bright, has all the Appearance of polifhed Brafs, and is more various as to its Form, than any other Mineral: however it is moft commonly found of a globulous Form, then of a cubical hexagonal, both regular and irregular Figure. It is folid; unless it be rendered foft by a Mixture of foft Stones and Earths: when ftruck with a Steel, it gives Sparks like a Flint: when brought near a gentle Fire, it foon buifts, with a crackling Noife; and emits fmall Flames almoft fulphureous: it changes its yellow Colour into a dark red, and its neat Surface into a dufty one. It is very rich in Sulphur, and contains one quarter, fometimes almoft one third Part of it. Moreover, there is always a Quantity of Iron lurking in it; its fulphureous Part is fometimes greater, fometimes lefs: and Henckel has found that it alfo contains a kind of Earth not metallick, and in a va rious Proportion as to the other Parts: which makes us eafily guefs, that the fpecifick Weight of the Py rites must be very various. The Author juft mentioned has, in his Treatife on Pyrites*, given us a very ample Hiftory of this Mineral, together with a very accurate Analysis of it.

317. There are very few Minerals altogether deftitute of Sulphur: but as the extracting of it would never pay the Charges, and they befides contain Metals and Semi-Metals in a greater Quantity; for this

Paritalogia, oder Kiefs Hiftorie, &c. gefertiget bon D. Jobann Friedrich Henckel. Leipzig. 1725, in 8°.

Reason,

Reason, we shall mention them in thofe Places, to which they properly belong (§ 310, 311).

318. We may alfo refer to this Clafs all the inflammable Minerals, that differ from Sulphur strictly fo called (§ 312.) by the Quantity and Quality of their Acids. Such are Naphta and Petroleum, that distil from Stones, or fwim upon the Waters of Fountains. They differ hardly among themselves, and are fometimes very limpid and thin, fometimes yellow and thick. But when thefe Matters are grown very thick, and have affumed a dark Colour, they are called Bi-. Pix Judaica; Asphaltum: and when at laft grown harder, they turn into a Stone called Gagates or feat. There occur befides, other the like Names of fulphureous Matters, which, however, feem hardly to fignify other Concretes, different from thofe juft mentioned.

319. The very fame (§ 318.) oily Mineral, when it hardens, and adheres to a ftony Matrix, becomes that kind of foffil Coal, called Stone-coal, Quarry-coat or Sea-coal which is a black concrete Body, easy to be cleft, confifting of Lamina's, and bright: much heavier than the foregoing (§ 318); not quite fo quickly inflammable, but preferving its Flame, when once kindled, longer and more violently than any other Fuel; leaving, after it is burnt, not fo much Afhes, as a Mafs half fcorificated, blackifh, fpungy, and often containing a yellow Pyrites (§ 316.) in it.

320. Amber, called in Latin Electrum, Succinum, of a blackish, dark yellow Colour; half transparent, frequently very tranfparent; light; finking however in Water; very hard, fo as not to foften at the Heat of boiling Water; melting nevertheless in a strong

Of which Kind is the greatest Plenty in fome Parts of England and Scotland, known by the Name of Kennel ccal, Staffordshirecoal, and S/otch coal: out of the firft feveral curious Veffels are turned and carved, as of Amber, of which Feat is a Species, and may be called black Amber.

Which is the common Fuel in London and the maritime Parts of England.

Fire,

Fire, foaming, and yielding a folid acid Salt, belongs alfo to this Clafs. It diffolves, by a Chemical Di ftillation, into. Oils, which are thin at first, and by degrees become thicker, and into an acid folid Salt: These Oils have fo much Affinity to Naphtha and Petroleum (§ 318), that we fee, if not always, at least moft frequently, Apothecaries and Druggifts ufse them in room of these natural Foffils. The Caput Mortuum remaining after the Distillation, is not unlike Bitumen (§ 318), and is even fold under that Name.

Of Arfenick, and arfenical Minerals.

321. The Crystalline, pure Arfenick defcribed (§ 17)*, is got out of the Mines under the fame Form, and looks white and dufty: however it is very feldom found natively fúch.

322. The fame (§ 321.) is digged out under the Form of a black or ath-coloured Stone, which being broken when fresh taken out, is within of a bright bluish White, which however, being exposed to the open Air, becomes dark and blackifh in a few Days.

323. Next to this the white Pyrites, which is heavy, bright, ftriking Fire against a Flint, and of a Figure altogether irregular, contains a very great Quantity of Arfenick, of Iron but little, more of Earth not metallick, and is most frequently found in Mines.

324. Orpiment, which is a Mineral of a Golden Colour, filled here and there with fmall Maffes of the Colour of Cinnabar, easy to be cleft, made up of Flakes, foft with fome Tenacity, bright when broken, contains a great Deal of Arfenick, lefs of mineral Sulphur (§ 312): wherefore, it burns dark in the Fire, giving a whitish blue Flame, with a moft thick white

Arfenick is vulgarly called in English Rats bane, and from its Colour is diftinguished into the white and yellow Rats bane, being the Poifon afually employed for deftroying Rats.

K

Smoak