PART IV.

Of the Origin and Formation of Metalls and Minerals.

W

HAT I can advance, with competent Certainty, about the Fluids of the Globe, the Sea, Springs, Rivers, and Rain, I propofe in the immediately foregoing or Third Part of this Essay. As in the Second Part of it I difpatch the Solids; Stone, Marble, Clay, and all the other Terreftrial Matter of it, which is digefted into Strata. That Part therefore comprehends the far greater Share of that Matter: and indeed all, excepting only Metalls and Minerals; which are found much more fparingly, and in leffer Parcels; being either enclosed in those Strata (lying

amongst

amongst the Sand, Earth, or other Matter whereof they confift) or contain'd in their perpendicular Fif fures. And thefe remaining ftill to be confider'd, I have allotted this Fourth Part to that Purpose.

To write of Metalls and Minerals intelligibly and with tolerable Perfpicuity, is a Task much more difficult than to write of either Animals or Vegetables. For thofe carry along with them fuch plain and evident Notes and Characters either of Difagreement, or Affinity with one another, that the feveral Kinds of them, and the fubordinate Species of each, are easily known and diftinguifh'd, even at firft Sight; the Eye alone being fully capable of judging and determining their mutual Relations, as well as their Differences.

But in the Mineral Kingdom the Matter is quite otherwife. Here is nothing regular, whatever fome may have pretended: nothing conftant or certain. Infomuch that a Man had need to have all his Senfes about him to use repeated Tryals and Inspections, and that with

:

all

all imaginable Care and Warynefs, truly and rightly to difcern and diftinguish Things, and all little enough. Here are fuch a vast Variety of Phenomena: and thofe, many of them, fo delufive, that 'tis very hard to escape Impofition and Miftake. Colour, or outward Appearance, is not at all to be trufted. A common Marcafite or Pyrites fhall have the Colour of Gold moft exactly and fhine with all the Brightness of it; and yet, upon Tryal, after all, yield nothing of Worth, but Vitriol, and a little Sulphur; whilft another Body, that hath only the Refemblance of an ordinary Peble, fhall yield a confiderable Quantity of Metallick and valuable Matter. So likewife a Mafs, which, to the Eye, appears to be nothing but meer fimple Earth, fhall, to the Smell or Tafte, difcover a plentifull Admixture of Sulphur, Alum, or fome other Mineral.

Nor may we with much better Security rely upon Figure, or external Form. Nothing more uncertain and varying. 'Tis ufual to meet with the very fame Metall, or Mineral,

Mineral, naturaly fhot into quite different Figures as 'tis to find quite different Kinds of them all of the fame Figure. And a Body that has the Shape and Appearance of a Diamond, may prove, upon Examination, to be nothing but Cryftall, or Selenites: nay perhaps only common Salt, or Alum, naturaly cryftalliz'd and shot into that Form.

So likewise if we look into their Situation, and Place in the Earth; fometimes we find them in the perpendicular Intervalls: fometimes in the Bodyes of the Strata, being interfpers'd amongst the Matter whereof they confift: and fometimes in both. Even, if I may fo fpeak, the gemmeous Matter it felf; with this only Difference, that thofe Gemms, e. g. Topazes, Amethyfts, or Emeralds, which grow in the Fiffures, are ordinarily cryftalliz'd, or fhot into angulated Figures: whereas, in the Strata, they are found in rude Lumps, and only like fo many yellow, purple, and green Pebles. Not but that even thefe, that are thus lodg'd in the Strata, are alfo fome

times

*Vid.

times found cryftalliz'd†, and in Form of Cubes, Rhombs, and the like. Or if we have refpect to Confect. 2. the Terrestrial Matter wherein they lye in thofe Strata, here we fhall meet with the fame Metall or Mineral embody'd in Stone, or lodg'd in Cole, that elsewhere we found in Marle, in Clay, or in Chalk*.

infra.

Vid. Confect. 3.

infra.

As much Inconftancy and Confufion is there in their Mixtures with each other, or their Combinations amonft themselves. For 'tis rare to find any of them pure, fimple, and

unmixt;

• The Crystallized Bodyes found in the perpen, dicular Intervalls are easily known from those which are lodged in the Strata, even by one who did not take them thence, or obferve them there. The former have always their Root, as the Jewellers call it, which is only the Abruptness at that End of the Body whereby it adhered to the Stone, or Sides of the Intervalls; which Abruptnefs is caufed by its being broke off from the faid Stone. Thofe which are found in the Strata of Earth, Sand, or the like, (having lain loofe therein) are intire, and want that Mark of Adhefion. But thofe which are inclosed in Stone, Marble, or fuch other folid Matter, being difficultly feparable from it, because of its Adhesion to all Sides of them, have commonly fome of that Matter ftill adhering to them, or at least Marks of its having been broke from them, on all their Sides; wherein these differ from thofe found in the perpendicular Intervalls, they adhering, as we have noted, by only one End Vid. Conf. 6. &c. infra.