fary fubftances are required to hinder their perfect vitrification;
and for fuch fubftances they can have recourfe to the Talky
clafs, the Foffils of which almost evade the force of fire, and
on that account furnish us with the fineft and beft ingredients.
On this principle it is evident, that no fpecies of clay whatever,
can be finer or fitter for the making up of China than these
hardened Talky Soap Clays, wherein nature has blended the
neceffary Fofils, Talk and Clay, ready for our ufe. Even a
very fine common white Clay, properly tempered and mixed in
fuitable proportions with our moift Talky Granite, or Moor-
ftone, impalpably triturated, may furnish us with the properest
materials to be had for a China manufactory. It remains,
however, ftill to be obferved, that the Clay for China must be
very fine, extremely white, and cleared from every heterogene
foil; for which reafon, in St. Stephen's and Breage parishes,
they pass it through many lotions with clear water, before it is
put
into cafks to be fent off. Where we have seen a natural or
adventitious mixture of Clay and Granite, with us, commonly
known by the name of Grouan Clay, it has always answered for
bricks to build fire places and furnaces with, equal to Stour-
bridge and other Clays; infomuch that plenty of it has been.
fent to Bristol, and the Welch Copper-works, for the purposes
before mentioned; befides that famous yellow Clay in the parish
of Lannant, which has produced fuch an hand fome income
every year to Humphry Mackworth Praed, Efq;. The manu-
factory, which was fet up within these few years at Truro, for the
making of crucibles, is a very notorious proof of the strength of
our Clays, when mixed with Granite, to resist the most intense
fire: no other crucibles are now used by our affayers; and the
inventor has received the appointed premium for the discovery,
from The Society for the encouragement of Arts, Manufactures,
and Commerce. Thefe crucibles have not one leaky neft among
fifty; and the foreign pots, which were used till lately, had
fcarcely fifty found crucibles among a hundred; fo that if the
proprietor knows how to advance his intereft, he may export
great quantities every year for foreign ufe, and fave a confider-
able fum to this kingdom, which formerly went out of it for
this neceffary article in metallurgy.

Stones are either common, or precious. There are also several forts of Stones peculiar to Metals, which are frequently met with in Mines, that, by their colours and confiftence, often denote either a profitable or barren Mine; fuch as Spar Stones, Quartz, and Fluors resembling Cryftal, by the Germans

termed

termed Fluffe, from their propenfity to melt in the fire, which are no bad fymptoms of Metals, except thofe Stones be hard, opaque, and untractable. There are feveral other kinds of Stones worthy of notice, which we omit here, and refer to their proper places, when we shall speak of the different kinds of Lodes with refpect to the Earth and Stones they contain. precious Stones, there are great diverfities of kinds, colours, and value; yet there are few met with by Mining in Europe, of any great intrinfick worth: the knowledge of precious Stones, however, is not properly the bufinefs of a Miner.

Of

Secondly, by Infpiffated Juices, and Mineral Waters, we mean all Mineral Sustances, dug, or flowing out of the earth, either in a coagulated or liquid form. Of the latter fort we fhall not speak further at present, but shall divide those of the firft kind into three forts, viz. Saline, Sulphureous, and Acid. Of the first are Sal Gem, or Sal Foffile, Nitre, and the like; of the second, are most kinds of Bitumens, as Naptha, Asphaltos or Pix Judaica, Petroleum, Sulphur, Pit-coal, &c. Lastly, the acid forts are Vitriol, or Copperas, of which there are great varieties, produced either by nature or art. Native Vitriol is made in the bowels of the earth of an aqueous liquor impregnated with an acid falt, and of a cupreous or martial Mineral, ftrictly united, both to a combuftible fulphureous fubstance, and to another body of a more fixed terreftrial nature. (Boyle). The common green Vitriol or Copperas of the fhops, is an artificial production; great quantities of which, are manufactured by my friend Ephraim Reinhold Seehl, Chymist, at Blackwall and Deptford.

Dr. Rouby, a curious foreigner, set on foot a manufactory of Roman or Blue Vitriol, at Treleigh in Redruth, about five and twenty years fince; which dropped, only with a lofs of ninety pounds, by means of fome difputes and difagreements among the perfons concerned. It was collected from the waters which were left from the lotions of Black Tin, after it had been calcined in the burning-house, for the discharge of its Mundick. This water, being strongly impregnated with vitriolick particles, after it had been decanted clear from its dregs, was kept conftantly boiling, by a gentle fire, for feven or eight days, in a leaden boiler; when being evaporated to a pellicle, it was drawn off, and set to cryftallize in proper veffels. The time for cryftallization, was generally three or five days, according to the different degrees of impregnation of the water; eight

tons of which, well faturated with vitriolick particles, would yield a ton of very fine blue Vitriol, far fuperior to the Hungarian, or any other I have yet feen; at that time, worth about eighty pounds, and the expence of making about fifty. The materials are fo plenty with us, that we could undertake to fupply the whole world with this merchandife from Cornwall, by a cheaper procefs than the foregoing. But the domeftick demand for this falt, does not exceed twelve or fourteen tons annum ; and our remote diftance from the centre of the kingdom, will occafion fo great a charge in commiffion, freight, carriage, &c. that it will hardly be worth the trouble and expence of apparatus and making. Befides, without a patent for the fole making and vending thereof, it would foon be in the hands of too many perfons, for the continuance and profperity of the undertaking. Add to this, that they now make it at Birmingham of what they call pickle, and render it at nearly half the price they formerly fold it for: and we imagine, that the continent may be fupplied from the Cyprus and Hungarian Mines with an inferior Vitriol, of courfe cheaper, and what may answer their purpofe almoft as well.

There are alfo other forts of Copperas, which are distinguished by their different colours, as Chalcitis, Melentaria, &c. which are only different degrees of the fame recrementitious Mineral, and are now very little regarded. Other acid Foffils, are native or rock Alum, or common Alum, which is made by art; but the Alom de Pluma, Alumen Plumofum, feems rather to be the Amianthus, Afbeftos, or Earth Flax, whofe fibres endure the fire and will not burn. The laft, however, is rather a Stone than a Mineral; and has been found in the parishes of Landawednack and St. Clare in Cornwall very fine and perfect. Dr. Grew in his Museum of the Royal Society, fays, "There is a "kind of Asbestos, which grows in veins in a Clay and Mun"dick Lode, between beds of a greenish earth, in our Cornish "Mines;" but we never yet faw any thing of the kind in them.

The fublimate of our white Mundick, if carefully fwept from the funnels of our burning-houses, and well feparated from the bituminous foot and fmoke mixed with it, may produce, by confined fufion, some of the best white Arsenick; and the more yellow Mundick may give a fine delicate ftraw coloured fort. If it is not fufficient of itself, an addition of one tenth Sulphur, will perfectly do it; and by a further addition of Sulphur, a

be obtained. But, if I am rightly fine red Arfenick may be obtained. very informed, the most profitable torture this Mineral can undergo, is the ruducing of it into a beautiful Ultramarine, which is more valuable than Gold itself.

The Society for the Encouragement of Arts, has repeatedly offered premiums for the best compofition to pay over hips bottoms, in order to defend them against marine worms, which abound fo much in fome parts of the East and West-Indian seas, that vessels new off the ftocks, have been frightfully bored in their firft voyage. Our county being altogether maritime, and the Mines being fituated in the most narrow part of it, between the two channels, many of our adroit Tinners are equally converfant with naval and fubterranean affairs. So true is this, that in St. Ives and Lelant, during the fishing season, they are wholly employed upon the water, to the great hinderance of the adjacent Mines; and when the fishing craft is laid up against the next season, the fishermen again become Tinners, and dive for employment into the depths of the earth. We have more than one inftance, of a common labouring Tinner, after he has many years worked under-ground, becoming fo complete a failor, as to be entrusted with the command of a large veffel to the Baltick, the Levant, or any other part of the globe. This may seem strange to fome of our readers; but if it were much to our prefent purpofe, we could make it appear, that there is in fome parts of the two employments a great analogy, notwithftanding the elemental difference. It is a maxim among us,

that a good Tinner makes a handy Sailor.

It is not, therefore, to be wondered at, that many of our Tinners and Sailors have reciprocally attended to the object of the above-mentioned premium: the poisonous qualities of our Mundick have engroffed their attention accordingly; and they have complied with every direction in regard to the payment of timber with this poifon, but all to no purpose. We have tried it in a preparation of our own, fubtilized in fuch manner, as to be free from thofe cracks after it is laid on, to which the Mineral, by its specifick gravity, when mixed with pitch and tar, is fubject. It will be needlefs to defcribe how we have tried it upon fome of his Majefty's packet boats at Falmouth, as the experiments did but partially fucceed to our wifh: fuffice it to say, that no payment, however deleterious to animal life, will anfwer our expectations, unless it can be laid on in such manner, and of such confiftence, as to be equally fmooth and

free

free from the leaft crack or feparation; and be of fuch impenetrable hardness when dry, as to equal Metal, which alone is proof against the piercing auger of the Teredo: even petrified wood may be bored by the jaws of this worm, which we are told will penetrate Stone itself. Mons. de la Voye fpeaks of an ancient wall in the Benedictines abbey at Caen in Normandy, fo eaten with worms, that a man may run his hand into moft of the cavities. (Philo. Trans.) Hence we will take upon us to fay, that no payment whatever, even the moft poifonous, will effect the refiftance required; for the worm firft of all introduces its auger, which is a callous, fhell-like, infenfible inftrument, through the matter which is laid upon the wood, and continues working, till it has made a deep impreffion into the substance of the timber, when it takes a turn, and works along with the grain of the wood, which it then feeds upon, and not before: whereby we fee, it has escaped beyond the defigned cause of its deftruction, before the vital or animal part of it comes into action; so that we may be affured, that no payment will secure our ships bottoms, but impenetrability itself.

A quantity of the preparation here spoken of, was fent fome time ago to an eminent fhip-builder at Rotherhithe, who returned for answer, "That he was very well fatisfied, the compofition would fulfil the moft fanguine expectations; but, he "thought it not the proper bufinefs of a fhipwright, to advance or encourage any fuch undertaking, however laudable in the eye of the publick; and he fuppofed every other artificer in "his way, would be of the fame mind:" and in confequence of this reafoning, a few hundreds weight of the preparation were thrown into the Thames. We likewife recommended a trial of it to another fhip-builder in this county, who ingenuously faid, "That he would firft wait fome trials of his own upon Mun"dick very finely pulverized:" but he would not regard, or did not understand, my reasons against the bare poffibility of his fuccefs.

The effect, however, that cannot be obtained by external application in the payment of a fhip's bottom, may be produced by previously faturating the planks of which the bottom is formed. The planks that are laid upon the bottom or fide of a ship, are first feafoned in hot water, in order that they may be flexible, and yield to the form and fhape of the mould, upon which they are laid. It is, therefore, only necessary to infuse and mix with the boiling medium, a quantity of the abovementioned