The truth of this thing, viz. That there resides natural Salt-petre in all Stones, which may be burnt into Lime, may be proved on this wise following:
Take of these Stones which Lime may be made of, ℥ ss. or ℥ j. powder it very fine, pour thereupon as much of the best Aqua-fortis: Place the Glass in which this matter is contained, in a warm place upon ashes or sand, that the stone may be dissolved in the Aqua-fortis: After it hath thus stood for about one quarter of an hour, take out your Glass out of the ashes or sand, though the stone be not wholly dissolved as yet, and pour thereon drop by drop, some Lixivium of wood, untill the ebullition of the Lee or Lixivium poured upon the dissolved stone ceaseth, and (the noise ceasing) you shall perceive some kind of Salt produced from them thus commixt, viz. from the dissolved stone and the Lixivium. Pour some common Water upon this Salt, so much as may serve to dissolve the Salt in a warm place, the solution being made let the Liquor be filtred, or be strained through some thin Linen cloth, that so the part of the stone undissolved, and the fæces may abide behind in the Filter or Linen cloth: The filtred Liquor must be coagulated into Salt by evaporating it away in a brass Vessel, then you are to weigh it: And now that we may exactly know, how much Salt-petre was in that ℥ ss. of the stone, you must proceed on farther thus:
Take the same quantity of Aqua-fortis as you used but now, about the solution of the Lime-stone, and pour thereon likewise the same quantity of Lixivium, that you used about the precipitation of the dissolved stone, and let there be made a precipitation, let the precipitated matter be coagulated into the substance of a salt, and then also weigh how much this quantity of salt is: and now, as much less weight, as you observe to be in this salt than in the first Salt in which the Lime-stone is, so much Salt-petre was there in that half ounce of Lime-stone. This is a most certain trial, and by this means may we most easily find how many pounds of Salt-petre, are contained in an hundred weight of stones.
NB. To the end that the proof you make, may be most certain, we must use the lesser Centenary, or hundred weight, as being more usual, and more accommodate for the trying of Metals.
And albeit, that the using of Aqua-fortis to this Operation, is altogether without profit, where you would extract that salt in great plenty out of the stones, yet notwithstanding, it is not so slight or trivial a thing to know a certain way of trying what stones do most abound with Salt-petre, that so if we have a mind to extract Salt-petre out of them, we may take those, in which it lies in a plentiful manner.
Besides, those stones which do commonly yield a Calx or Lime by Calcination, and which the Bricklayers use; there are found other stones, out of which there cannot be made any Lime by Calcination, and yet nevertheless, abundance of Salt-petre may be thence extracted without any previous Calcination. He that delights himself in this work, must exactly know aforehand such kind of stones: Forasmuch as no body would easily perswade himself that Salt-petre is contained in them. Nor do I think that ever afore this time the way of extracting Salt-petre out of these kinds of stones was used; but whether there was no body that knew that there was Such a Salt contained in them, or judged it a thing not to be regarded, this I know not. But this I know well enough that that way of extracting Salt-petre out of them was never observed and used in Germany, though there lies a most notable quantity of Petre in them, and easily extractable thence, did we but know the way.
Therefore, forasmuch as there is plenty enough of such stones in all places, and that Salt-petre may easilier be made of them, than of wood, I could not forbear, but must needs open and disclose this artifice for the good of the Country, and clearly explain it in this place.
Therefore, as concerning those stones which are here mentioned, there is such a plentiful store of them in most places, that they even make whole Mountains; they are in substance like a soft and tender stone, whitish in colour, [or of a shining colour] ashy colour’d or reddish, and are easily broken, and may be fashioned into all kind of shapes, or figures; and therefore they are frequently used about building Houses, for the making various Ornaments about the House, as for the corners of the Houses, the Doors, Windows, Steps or Stairs, or other External Ornaments. As long as they are yet in the Mountain, and not exposed to the air, they are of a considerable hardness enough, and do always hold it. When being used about Buildings, they are put in such places, where they may abide at all times dry, or else always moist.
But if so be they are one while dry, and another while moist, and are always obvious to the air [or weather] they easily become soft, and there scales off from them yearly, a little portion of the back of a Knifes thickness, like Meal, so that they are yearly lessen’d, and are not at all fit to build stable, or durable Houses with. The Stone-Cutters can easily distinguish these kind of stones from others, nor do they willingly use them where there is plenty of others to be had. And now, if you should go about to make your trial with these stones, like as you did with those that they make Lime of, according to the afore delivered Probation, so to know what quantity of Salt-petre is contained in them, it will not succeed so, because the Salt-petre becomes Volatile in the Calcination of it, and doth for the most part fly away into the air: and much less can you with [bare] water extract ought out of the Crude, and not Calcined stones; for such do not yield any Salt-petre at all, unless they have been placed in a moist air for about half a years space, whereby they may of themselves fall in pieces; for being so ordered, they easily yield forth their saltness to the water that is poured on them, and consequently yield plenty of Salt-petre. Of which thing, this is a most certain Testimony, if (viz.) such stones are laid in some dry place, whereto the Rain cannot come, and we do most frequently sprinkle them with common water, and they do thereby turn into a powder. And if it fall out otherwise, ’tis a sign that there is very little Salt-petre to be found in them, and that the labour you shall bestow about them will be in vain. But such stones as grow soft, and fall in pieces, in six or eight Months time, do promise notable Rewards for your Labour, viz. a great quantity of the wisht for salt; an hundred weight of these kind of stones thus fallen in pieces, will easily yield you ten pound of Salt-petre, more or less according to the Condition of the stone. The extracting of the Lee, or salt, is done with common water, in the same manner as the Lixivium is otherwise extracted out of that Earth which is digg’d up in the Stables where Beasts stand; which way of extracting Salt-petre, of coagulating and perfecting it, is clearly and perfectly enough described by Lazarus Ercker, heretofore the Emperours chief Overseer of the Metallick Affairs, in his most experienced Book of his Art of the proving of Metals; insomuch, that I esteem him to have rendred the hardest, or most difficult part, very clear, and therefore I will referr the well minded Reader thither.
But for as much as every one cannot buy himself a Book of such great bulk, only to get thereby the knowledge of the way of extracting and evaporating Salt-petre, I have judged it worth while to set down here for the sake of the Chymical Students, such directions as the aforesaid Lazarus Ercker hath delivered us hereabouts. For I was never of the mind to cast off such things as have been well delivered by other men; I only add unto them, those things that are mine: Let others do the like, that are the Authors of any new thing, that so there may arise some benefit thereby unto our Neighbours, for whose sake, that we may (viz.) serve them, the most great and blessed God hath bestowed on us such various knowledge.