of the produce in white Tin; the other two-thirds he has for himself to pay his coft and charges.

Proceeding upon this fingle principle, that the force of water, properly applied and introduced among the particles of Tin Ore and the fordes mixed with it, will difperfe the latter and leave the former at reft for them to collect and treafure up, they vary their operations inconceivably, conducting them with great ingenuity, leffening, encreafing, diffufing, or contracting their water, the great inftrument of purity, as the fize, weight, and combinations of the Metal and its feeders require; and that with great eafe, cheapnefs, and regularity, throughout the feveral proceffes.

Hence, this business of dreffing is a particular trade, entirely different from that of the labouring Miner; and is best learned under a master workman, who makes it his fole occupation to follow the ftamping mill and the works belonging thereto. This mafter workman hires boys from feven years old to eighteen, gives the former about three fhillings a month, and raises their wages as they advance in years and workmanship, till they have man's wages, viz. at the leaft twenty-four fhillings, at the highest thirty fhillings month. This is of double benefit to the poor parents; and the boys being taken in fo young, become healthy and hardy by ufing themfelves to cold, and to work with naked wet feet all day; and they learn early to contribute to their own maintenance. Each stamping mill which has conftant work and water, will employ one man and five boys; and one hundred facks are carried, ftamped, and dreffed, in the space of a few days, at the average rate of about fourpence fack, or one guinea and a half hundred.

We shall here observe, that even burnt leavings of Tin are often confiderably valuable, efpecially if they are cupreous; and even the poorest of these leavings bring ten or twenty fhillings

ton; which is better than to throw them away, as was the cafe no further back than forty years. All burnt leavings taken from Tin-stuff, till the year 1735, were esteemed good for nothing. But in that year there were several small parcels lying on fundry stamps plots in this parish, which induced Mr. Morgan Bevan, an old experienced affayer, to try whether he could reduce them into Metal. For the first time he affayed a sample of three tons; and, to his own great surprise, as well as that of others, he found that he could give seven pounds four shillings

and

and fixpence ton for them, which he actually did, and presently after bought feveral parcels more of Meffrs. Carter, Reynolds, Penrofe, Cornifh, &c. the principal Tin dreffers of those days. From that time all burnt leavings were taken much care of, provided they were fufficiently impregnated with Copper; for fome of them are merely Mundick, with little or no Copper in them. When the Brass-wire Company carried on the great Tin Mine of Chacewater, before this discovery they caft away fome hundred tons of burnt leavings, to their great prejudice; but fince that time there have been large quantities fold from the fame Mine.

The very water in which burnt Tin is wafhed, may be converted to a useful and profitable account, either by evaporation to a pellicle for cryftallization of Copper, commonly called Blue or Roman Vitriol; or for the precipitation of Copper by the medium of Iron, laid in veffels filled with this vitriolick water. The precipitation of Copper by Iron, is too generally understood to make an explanation neceffary here; but we have obferved among our Copper precipitate, where it has been effected by a very strong folution with the cleaneft Iron, several pieces of malleable Copper, fome of them retaining the form of the Iron, like incruftations fallen off from it. Hence it seems as if there was a degree of attraction between the Iron and the particles of Copper, floating in the water; as well as the more obvious attraction between the acid and the Iron. Muft not the particles of Copper thus attracted, cohere by their own magnetism, or the attraction of cohesion ?

It may not be improper to add how far this quality has already tended or may tend to the advantage of the publick. Perhaps the hiftory of its rife and progress in this country, and in Ireland, may ferve to illuftrate that matter. About fixty years ago, this phenomenon was firft obferved by Mr. Cofter in Chacewater Mine near this town; for after he had drawn out the water, which had been in the Mine for several years, he found the poll of a pick-axe wholly encrufted with a cafe of malleable Copper between two and three pounds weight. This it was justly fuppofed was obferved by the workmen, fome of whom afterwards fettled at Cranbaun Mine in the county of Wicklow in Ireland. The water of Cranbaun having this vitriolick acid in a very high degree, Capt. Thomas Butler, who was one of Redruth, and manager of that Mine, perfuaded the proprietors to adopt the scheme of precipitating Copper, of

which they have made for many years paft and now continue to make very confiderable profit. They dig pits at proper diftances in the Adit, (or fo near as to admit the water) in which pit they place wooden rails, fomewhat like a bottle rack, fo as to fufpend the Iron thereon. They put in many tons at a time; and, in about fix weeks, the Iron is totally diffolved. The precipitated Copper is then taken out, fit for fale; the greatest part in the form of our Goffan pounded, with feveral grains of pure Copper interfperfed.

An attempt of this kind was fome years paft made in HuclCrafty, but without fuccefs; for the water being in one part of the Mine only, and in no greater quantity than would run through a quill, was too much diluted by other water mixing with it in the hutch where the Iron was placed; befides, the Iron itself was very rufty which will always obftruct the success, unless the water is in the highest degree impregnated with the acid. A small and ready experiment proves this; for take a bright piece of Iron, fuch as a key, or polished knife, and immerse it in the water for half a minute, and it will be stained of a Copper colour. Many Mines in this county have some rills of this water, so as to do confiderable mischief, without having as yet (perhaps for want of proper attention) applied it to this use.

But though we may date the firft hints relating to this matter in England and Ireland from the foregoing discovery in Chacewater, it is no new thing in other countries. Brown mentions it in his travels into Hungary, as a profitable appendage to the Mining of that country. Dr. Rutty, in his Natural History of Dublin, fays, "Our water at Cranbaun in the county of Wicklow, may well vie with those of Herengrund and Ciment "in Hungary. Of ours I received the following account in the year 1765 from a perfon converfant in these matters."

"It is faid to tranfmute Iron into Copper; but the fact is, "that it precipitates its contained Copper upon Iron bars im"merfed. It continues in its full ftrength; and, in feven years "laft paft, yielded to its proprietors a fum no less than feven"teen thousand two hundred and fifty-nine pounds eighteen "fhillings and ninepence halfpenny, and all this without any

expence of fuel and men. The precipitate thus formed being "fluxed, yields above half of pure Copper: for an ounce gave "twelve pennyweights and eighteen grains in one experiment, "and thirteen pennyweights twelve grains in another."

CHAP.

To the Right Hon Humphry, Horice M.P.

Lord Warden of the Stannaries and Showard of the Dutchy of Cornwall. This Plate Engraved at his Expence

Cxpence is most gratefully Inscribed, by by WV." Pryce