De Re Metallica Part 35

[4] _Cadmia bituminosa_. The description of this substance by Agricola, given below, indicates that it was his term for the complex copper-zinc-a.r.s.enic-cobalt minerals found in the well-known, highly bituminous, copper schists at Mannsfeld. The later Mineralogists, Wallerius (_Mineralogia_, Stockholm, 1747), Valmont De Bomare (_Mineralogie_, Paris, 1762), and others a.s.sume Agricola's _cadmia bituminosa_ to be "black a.r.s.enic" or "a.r.s.enic noir," but we see no reason for this a.s.sumption. Agricola's statement (_De Nat. Foss._, p.

369) is "... the schistose stone dug up at the foot of the Melibocus Mountains, or as they are now called the Harz (_Hercynium_), near Eisleben, Mannsfeld, and near Hettstedt, is similar to _spinos_ (a bituminous substance described by Theophrastus), if not identical with it. This is black, bituminous, and cupriferous, and when first extracted from the mine it is thrown out into an open s.p.a.ce and heaped up in a mound. Then the lower part of the mound is surrounded by f.a.ggots, on to which are likewise thrown stones of the same kind. Then the f.a.ggots are kindled and the fire soon spreads to the stones placed upon them; by these the fire is communicated to the next, which thus spreads to the whole heap. This easy reception of fire is a characteristic which bitumen possesses in common with sulphur. Yet the small, pure and black bituminous ore is distinguished from the stones as follows: when they burn they emit the kind of odour which is usually given off by burning bituminous coal, and besides, if while they are burning a small shower of rain should fall, they burn more brightly and soften more quickly.

Indeed, when the wind carries the fumes so that they descend into nearby standing waters, there can be seen floating in it something like a bituminous liquid, either black, or brown, or purple, which is sufficient to indicate that those stones were bituminous. And that genus of stones has been recently found in the Harz in layers, having occasionally gold-coloured specks of pyrites adhering to them, representing various flat sea-fish or pike or perch or birds, and poultry c.o.c.ks, and sometimes salamanders."

[5] _Atramentum sutorium rubrum_. Literally, this would be red vitriol.

The German translation gives _rot kupferwa.s.ser_, also red vitriol. We must confess that we cannot make this substance out, nor can we find it mentioned in the other works of Agricola. It may be the residue from leaching roasted pyrites for vitriol, which would be reddish oxide of iron.

[6] The statement "elsewhere" does not convey very much more information. It is (_De Nat. Fos._, p. 253): "When Goslar pyrites and Eisleben (copper) schists are placed on the pyre and roasted for the third time, they both exude a certain substance which is of a greenish colour, dry, rough, and fibrous (_tenue_). This substance, like asbestos, is not consumed by the fire. The schists exude it more plentifully than the pyrites." The _Interpretatio_ gives _federwis_, as the German equivalent of _amiantus_ (asbestos). This term was used for the feathery alum efflorescence on aluminous slates.

[7] Bearing in mind that bituminous cadmia contained a.r.s.enical-cobalt minerals, this substance "resembling _pompholyx_" would probably be a.r.s.enic oxide. In _De Natura Fossilium_ (p. 368). Agricola discusses the _pompholyx_ from _cadmia_ at length and p.r.o.nounces it to be of remarkably "corrosive" quality. (See also note on p. 112.)

[8] HISTORICAL NOTE ON CRUSHING AND CONCENTRATION OF ORES. There can be no question that the first step in the metallurgy of ores was direct smelting, and that this antedates human records. The obvious advantages of reducing the bulk of the material to be smelted by the elimination of barren portions of the ore, must have appealed to metallurgists at a very early date. Logically, therefore, we should find the second step in metallurgy to be concentration in some form. The question of crushing is so much involved with concentration that we have not endeavoured to keep them separate. The earliest indication of these processes appears to be certain inscriptions on monuments of the IV Dynasty (4,000 B.C.?) depicting gold washing (Wilkinson, The Ancient Egyptians, London, 1874, II, p. 137). Certain stelae of the XII Dynasty (2,400 B.C.) in the British Museum (144 Bay 1 and 145 Bay 6) refer to gold washing in the Sudan, and one of them appears to indicate the working of gold ore as distinguished from alluvial. The first written description of the Egyptian methods--and probably that reflecting the most ancient technology of crushing and concentration--is that of Agatharchides, a Greek geographer of the second Century B.C. This work is lost, but the pa.s.sage in question is quoted by Diodorus Siculus (1st Century B.C.) and by Photius (died 891 A.D.). We give Booth's translation of Diodorus (London, 1700, p. 89), slightly amended: "In the confines of Egypt and the neighbouring countries of Arabia and Ethiopia there is a place full of rich gold mines, out of which with much cost and pains of many labourers gold is dug. The soil here is naturally black, but in the body of the earth run many white veins, shining like white marble, surpa.s.sing in l.u.s.tre all other bright things. Out of these laborious mines, those appointed overseers cause the gold to be dug up by the labour of a vast mult.i.tude of people. For the Kings of Egypt condemn to these mines notorious criminals, captives taken in war, persons sometimes falsely accused, or against whom the King is incens'd; and not only they themselves, but sometimes all their kindred and relations together with them, are sent to work here, both to punish them, and by their labour to advance the profit and gain of the Kings. There are infinite numbers upon these accounts thrust down into these mines, all bound in fetters, where they work continually, without being admitted any rest night or day, and so strictly guarded that there is no possibility or way left to make an escape. For they set over them barbarians, soldiers of various and strange languages, so that it is not possible to corrupt any of the guard by discoursing one with another, or by the gaining insinuations of familiar converse. The earth which is hardest and full of gold they soften by putting fire under it, and then work it out with their hands.

The rocks thus soften'd and made more pliant and yielding, several thousands of profligate wretches break in pieces with hammers and pickaxes. There is one artist that is the overseer of the whole work, who marks out the stone, and shows the labourers the way and manner how he would have it done. Those that are the strongest amongst them that are appointed to this slavery, provided with sharp iron pickaxes, cleave the marble-shining rock by mere force and strength, and not by arts or sleight-of-hand. They undermine not the rock in a direct line, but follow the bright shining vein of the mine. They carry lamps fastened to their foreheads to give them light, being otherwise in perfect darkness in the various windings and turnings wrought in the mine; and having their bodies appearing sometimes of one colour and sometimes of another (according to the nature of the mine where they work) they throw the lumps and pieces of the stone cut out of the rock upon the floor. And thus they are employed continually without intermission, at the very nod of the overseer, who lashes them severely besides. And there are little boys who penetrate through the galleries into the cavities and with great labour and toil gather up the lumps and pieces hewed out of the rock as they are cast upon the ground, and carry them forth and lay them upon the bank. Those that are over thirty years of age take a piece of the rock of such a certain quant.i.ty, and pound it in a stone mortar with iron pestles till it be as small as a vetch; then those little stones so pounded are taken from them by women and older men, who cast them into mills that stand together there near at hand in a long row, and two or three of them being employed at one mill they grind a certain measure given to them at a time, until it is as small as fine meal. No care at all is taken of the bodies of these poor creatures, so that they have not a rag so much as to cover their nakedness, and no man that sees them can choose but commiserate their sad and deplorable condition. For though they are sick, maimed, or lame, no rest nor intermission in the least is allowed them; neither the weakness of old age, nor women's infirmities are any plea to excuse them; but all are driven to their work with blows and cudgelling, till at length, overborne with the intolerable weight of their misery, they drop down dead in the midst of their insufferable labours; so that these miserable creatures always expect the future to be more terrible than even the present, and therefore long for death as far more desirable than life.

"At length the masters of the work take the stone thus ground to powder, and carry it away in order to perfect it. They spread the mineral so ground upon a broad board, somewhat sloping, and pouring water upon it, rub it and cleanse it; and so all the earthy and drossy part being separated from the rest by the water, it runs off the board, and the gold by reason of its weight remains behind. Then washing it several times again, they first rub it lightly with their hands; afterward they draw off any earthy and drossy matter with slender sponges gently applied to the powdered dust, till it be clean, pure gold. At last other workmen take it away by weight and measure, and these put it into earthen pots, and according to the quant.i.ty of the gold in every pot they mix with it some lead, grains of salt, a little tin and barley bran. Then, covering every pot close, and carefully daubing them over with clay, they put them in a furnace, where they abide five days and nights together; then after a convenient time that they have stood to cool, nothing of the other matter is to be found in the pots but only pure, refined gold, some little thing diminished in the weight. And thus gold is prepared in the borders of Egypt, and perfected and completed with so many and so great toils and vexations. And, therefore, I cannot but conclude that nature itself teaches us, that as gold is got with labour and toil, so it is kept with difficulty; it creates everywhere the greatest cares; and the use of it is mixed both with pleasure and sorrow."

The remains at Mt. Laurion show many of the ancient mills and concentration works of the Greeks, but we cannot be absolutely certain at what period in the history of these mines crushing and concentration were introduced. While the mines were worked with great activity prior to 500 B.C. (see note 6, p. 27), it was quite feasible for the ancient miner to have smelted these argentiferous lead ores direct. However, at some period prior to the decadence of the mines in the 3rd Century B.C., there was in use an extensive system of milling and concentration. For the following details we are indebted mostly to Edouard Ardaillon (_Les Mines Du Laurion dans l'Antiquite_, Chap. IV.). The ore was first hand-picked (in 1869 one portion of these rejects was estimated at 7,000,000 tons) and afterward it was apparently crushed in stone mortars some 16 to 24 inches in diameter, and thence pa.s.sed to the mills. These mills, which crushed dry, were of the upper and lower millstone order, like the old-fashioned flour mills, and were turned by hand. The stones were capable of adjustment in such a way as to yield different sizes.

The sand was sifted and the oversize returned to the mills. From the mills it was taken to washing plants, which consisted essentially of an inclined area, below which a ca.n.a.l, sometimes with riffles, led through a series of basins, ultimately returning the water again to near the head of the area. These washing areas, constructed with great care, were made of stone cemented over smoothly, and were so efficiently done as to remain still intact. In washing, a workman brushed upward the pulp placed on the inclined upper portion of the area, thus concentrating there a considerable proportion of the galena; what escaped had an opportunity to settle in the sequence of basins, somewhat on the order of the buddle. A quotation by Strabo (III, 2, 10) from the lost work of Polybius (200-125 B.C.) also indicates concentration of lead-silver ores in Spain previous to the Christian era: "Polybius speaking of the silver mines of New Carthage, tells us that they are extremely large, distant from the city about 20 stadia, and occupy a circuit of 400 stadia, that there are 40,000 men regularly engaged in them, and that they yield daily to the Roman people (a revenue of) 25,000 drachmae. The rest of the process I pa.s.s over, as it is too long, but as for the silver ore collected, he tells us that it is broken up, and sifted through sieves over water; that what remains is to be again broken, and the water having been strained off, it is to be sifted and broken a third time.

The dregs which remain after the fifth time are to be melted, and the lead being poured off, the silver is obtained pure. These silver mines still exist; however, they are no longer the property of the state, neither these nor those elsewhere, but are possessed by private individuals. The gold mines, on the contrary, nearly all belong to the state. Both at Castlon and other places there are singular lead mines worked. They contain a small proportion of silver, but not sufficient to pay for the expense of refining." (Hamilton's Translation, Vol. I., p.

222). While Pliny gives considerable information on vein mining and on alluvial washing, the following obscure pa.s.sage (x.x.xIII, 21) appears to be the only reference to concentration of ores: "That which is dug out is crushed, washed, roasted, and ground to powder. This powder is called _apitascudes_, while the silver (lead?) which becomes disengaged in the furnace is called _sudor_ (sweat). That which is ejected from the chimney is called _scoria_ as with other metals. In the case of gold this _scoria_ is crushed and melted again." It is evident enough from these quotations that the Ancients by "washing" and "sifting," grasped the practical effect of differences in specific gravity of the various components of an ore. Such processes are barely mentioned by other mediaeval authors, such as Theophilus, Biringuccio, etc., and thus the account in this chapter is the first tangible technical description.

Lead mining has been in active progress in Derbyshire since the 13th century, and concentration was done on an inclined board until the 16th century, when William Humphrey (see below) introduced the jigging sieve.

Some further notes on this industry will be found in note 1, p. 77.

However, the buddle and strake which appear at that time, are but modest improvements over the board described by Agatharchides in the quotation above.

The ancient crushing appliances, as indicated by the ancient authors and by the Greek and Roman remains scattered over Europe, were hand-mortars and mill-stones of the same order as those with which they ground flour.

The stamp-mill, the next advance over grinding in mill-stones, seems to have been invented some time late in the 15th or early in the 16th centuries, but who invented it is unknown. Beckmann (Hist. of Inventions, II, p. 335) says: "In the year 1519 the process of sifting and wet-stamping was established at Joachimsthal by Paul Grommestetter, a native of Schwarz, named on that account the Schwarzer, whom Melzer praises as an ingenious and active washer; and we are told that he had before introduced the same improvements at Schneeberg. Soon after, that is in 1521, a large stamping-work was erected at Joachimsthal, and the process of washing was begun. A considerable saving was thus made, as a great many metallic particles were before left in the washed sand, which was either thrown away or used as mortar for building. In the year 1525, Hans Portner employed at Schlackenwalde the wet method of stamping, whereas before that period the ore there was ground. In the Harz this invention was introduced at Wildenmann by Peter Philip, who was a.s.say-master there soon after the works at the Upper Harz were resumed by Duke Henry the Younger, about the year 1524. This we learn from the papers of Herdan Hacke or Haecke, who was preacher at Wildenmann in 1572."

In view of the great amount of direct and indirect reference to tin mining in Cornwall, covering four centuries prior to Agricola, it would be natural to expect some statement bearing upon the treatment of ore.

Curiously enough, while alluvial washing and smelting of the black-tin are often referred to, there is nothing that we have been able to find, prior to Richard Carew's "Survey of Cornwall" (London, 1602, p. 12) which gives any tangible evidence on the technical phases of ore-dressing. In any event, an inspection of charters, tax-rolls, Stannary Court proceedings, etc., prior to that date gives the impression that vein mining was a very minor portion of the source of production. Although Carew's work dates 45 years after Agricola, his description is of interest: "As much almost dooth it exceede credite, that the Tynne, for and in so small quant.i.tie digged up with so great toyle, and pa.s.sing afterwards thorow the managing of so many hands, ere it comes to sale, should be any way able to acquite the cost: for being once brought above ground in the stone, it is first broken in peeces with hammers; and then carryed, either in waynes, or on horses' backs, to a stamping mill, where three, and in some places sixe great logges of timber, bounde at the ends with yron, and lifted up and downe by a wheele, driven with the water, doe break it smaller. If the stones be over-moyst, they are dried by the fire in an yron cradle or grate. From the stamping mill, it pa.s.seth to the crazing mill, which betweene two grinding stones, turned also with a water-wheel, bruseth the same to a find sand; howbeit, of late times they mostly use wet stampers, and so have no need of the crazing mills for their best stuffe, but only for the crust of their tayles. The streame, after it hath forsaken the mill, is made to fall by certayne degrees, one somewhat distant from another; upon each of which, at every discent, lyeth a greene turfe, three or foure foote square, and one foote thick. On this the Tinner layeth a certayne portion of the sandie Tinne, and with his shovel softly tosseth the same to and fro, that, through this stirring, the water which runneth over it may wash away the light earth from the Tinne, which of a heavier substance lyeth fast on the turfe. Having so clensed one portion, he setteth the same aside, and beginneth with another, until his labour take end with his taske. The best of those turfes (for all sorts serve not) are fetched about two miles to the eastwards of S.

Michael's Mount, where at low water they cast aside the sand, and dig them up; they are full of rootes of trees, and on some of them nuts have been found, which confirmeth my former a.s.sertion of the sea's intrusion.

After it is thus washed, they put the remnant into a wooden dish, broad, flat, and round, being about two foote over, and having two handles fastened at the sides, by which they softly shogge the same to and fro in the water betweene their legges, as they sit over it, untill whatsoever of the earthie substance that was yet left be flitted away.

Some of later time, with a sleighter invention, and lighter labour, doe cause certayne boyes to stir it up and down with their feete, which worketh the same effect; the residue, after this often clensing, they call Blacke Tynne."

It will be noticed that the "wet stampers" and the buddle--worked with "boyes feete"--are "innovations of late times." And the interesting question arises as to whether Cornwall did not derive the stamp-mill, buddle, and strake, from the Germans. The first adequate detailed description of Cornish appliances is that of Pryce (_Mineralogia Cornubiensis_, London, 1778) where the apparatus is identical with that described by Agricola 130 years before. The word "stamper" of Cornwall is of German origin, from _stampfer_, or, as it is often written in old German works, _stamper_. However, the pursuit of the subject through etymology ends here, for no derivatives in German can be found for buddle, tye, strake, or other collateral terms. The first tangible evidence of German influence is to be found in Carew who, continuing after the above quotation, states: "But sithence I gathered stickes to the building of this poore nest, Sir Francis G.o.dolphin (whose kind helpe hath much advanced this my playing labour) entertained a Dutch Mynerall man, and taking light from his experience, but building thereon farre more profitable conclusions of his owne invention, hath practised a more saving way in these matters, and besides, made Tynne with good profit of that refuse which Tynners rejected as nothing worth." Beyond this quotation we can find no direct evidence of the influence of "Dutch Mynerall men" in Cornish tin mining at this time. There can be no doubt, however, that in copper mining in Cornwall and elsewhere in England, the "Dutch Mynerall men" did play a large part in the latter part of the 16th Century. Pettus (_Fodinae Regales_, London, 1670, p. 20) states that "about the third year of Queen Elizabeth (1561) she by the advice of her Council sent over for some Germans experienced in mines, and being supplied, she, on the tenth of October, in the sixth of her reign, granted the mines of eight counties ... to Houghsetter, a German whose name and family still continue in Cardiganshire." Elizabeth granted large mining rights to various Germans, and the opening paragraphs of two out of several Charters may be quoted in point. This grant is dated 1565, and in part reads: "ELIZABETH, by the Grace of G.o.d, Queen of England, France, and Ireland, Defender of the Faith, &c. To all Men to whom these Letters Patents shall come, Greeting. Where heretofore we have granted Privileges to Cornelius de Voz, for the Mining and Digging in our Realm of England, for Allom and Copperas, and for divers Ewers of Metals that were to be found in digging for the said Allom and Copperas, incidently and consequently without fraud or guile, as by the same our Privilege may appear. And where we also moved, by credible Report to us made, of one Daniel Houghsetter, a German born, and of his Skill and Knowledge of and in all manner of Mines, of Metals and Minerals, have given and granted Privilege to Thomas Thurland, Clerk, one of our Chaplains, and Master of the Hospital of Savoy, and to the same Daniel, for digging and mining for all manner of Ewers of Gold, Silver, Copper, and Quicksilver, within our Counties of York, Lancaster, c.u.mberland, Westmorland, Cornwall, Devon, Gloucester, and Worcester, and within our Princ.i.p.ality of Wales; and with the same further to deal, as by our said Privilege thereof granted and made to the said Thomas Thurland and Daniel Houghsetter may appear. _And_ we now being minded that the said Commodities, and all other Treasures of the Earth, in all other Places of our Realm of England...." On the same date another grant reads: "ELIZABETH, by the Grace of G.o.d, Queen of England, France, and Ireland, Defender of the Faith, &c. To all Men to whom these our Letters Patents shall come, Greeting. Where we have received credible Information that our faithful and well-beloved Subject William Humfrey, Saymaster of our Mint within our Tower of London, by his great Endeavour, Labour, and Charge, hath brought into this our Realm of England one Christopher Shutz, an Almain, born at _St. Annen Berg_, under the Obedience of the Electer of Saxony; a Workman as it is reported, of great Cunning, Knowledge, and Experience, as well in the finding of the Calamin Stone, call'd in Latin, _lapis calaminaris_, and in the right and proper use and commodity thereof, for the Composition of the mix'd Metal commonly call'd _latten_, etc." Col. Grant-Francis, in his most valuable collection (Smelting of Copper in the Swansea District, London, 1881) has published a collection of correspondence relating to early mining and smelting operations in Great Britain. And among them (p. 1., etc.) are letters in the years 1583-6 from William Carnsewe and others to Thomas Smyth, with regard to the first smelter erected at Neath, which was based upon copper mines in Cornwall. He mentions "Mr. Weston's (a partner) provydence in bringynge hys Dutch myners hether to aplye such businys in this countrye ys more to be commendyd than his ignorance of our countrymen's actyvytyes in suche matters." The princ.i.p.al "Dutche Mineral Master" referred to was one Ulrick Frosse, who had charge of the mine at Perin Sands in Cornwall, and subsequently of the smelter at Neath. Further on is given (p. 25) a Report by Jochim Gaunse upon the Smelting of copper ores at Keswick in c.u.mberland in 1581, referred to in note 2, p. 267. The Daniel Hochstetter mentioned in the Charter above, together with other German and English gentlemen, formed the "Company of Mines Royal" and among the properties worked were those with which Gaunse's report is concerned. There is in the Record Office, London (Exchequer K.R. Com. Derby 611. Eliz.) the record of an interesting inquisition into Derbyshire methods in which a then recent great improvement was the jigging sieve, the introduction of which was due to William Humphrey (mentioned above). It is possible that he learned of it from the German with whom he was a.s.sociated. Much more evidence of the activity of the Germans in English mining at this period can be adduced.

On the other hand, Cornwall has laid claims to having taught the art of tin mining and metallurgy to the Germans. Matthew Paris, a Benedictine monk, by birth an Englishman, who died in 1259, relates (_Historia Major Angliae_, London, 1571) that a Cornishman who fled to Germany on account of a murder, first discovered tin there in 1241, and that in consequence the price of tin fell greatly. This statement is recalled with great persistence by many writers on Cornwall. (Camden, _Britannia_, London, 1586; Borlase, Natural History of Cornwall, Oxford, 1758; Pryce, _Mineralogia Cornubiensis_, London, 1778, p. 70, and others).

[11] _Lapidibus liquescentibus_. (See note 15, p. 380).

[12] HISTORICAL NOTE ON AMALGAMATION. The recovery of gold by the use of mercury possibly dates from Roman times, but the application of the process to silver does not seem to go back prior to the 16th Century.

Quicksilver was well-known to the Greeks, and is described by Theophrastus (105) and others (see note 58, p. 432, on quicksilver).

However, the Greeks made no mention of its use for amalgamation, and, in fact, Dioscorides (V, 70) says "it is kept in vessels of gla.s.s, lead, tin or silver; if kept in vessels of any other kind it consumes them and flows away." It was used by them for medicinal purposes. The Romans amalgamated gold with mercury, but whether they took advantage of the principle to recover gold from ores we do not know. Vitruvius (VII, 8) makes the following statement:--"If quicksilver be placed in a vessel and a stone of a hundred pounds' weight be placed on it, it will swim at the top, and will, notwithstanding its weight, be incapable of pressing the liquid so as to break or separate it. If this be taken out, and only a single scruple of gold be put in, that will not swim, but immediately descend to the bottom. This is a proof that the gravity of a body does not depend on its weight, but on its nature. Quicksilver is used for many purposes; without it, neither silver nor bra.s.s can be properly gilt. When gold is embroidered on a garment which is worn out and no longer fit for use, the cloth is burnt over the fire in earthen pots; the ashes are thrown into water and quicksilver added to them; this collects all the particles of gold and unites with them. The water is then poured off and the residuum placed in a cloth, which, when squeezed with the hands, suffers the liquid quicksilver to pa.s.s through the pores of the cloth, but retains the gold in a ma.s.s within it." (Gwilt's Trans., p. 217). Pliny is rather more explicit (x.x.xIII, 32): "All floats on it (quicksilver) except gold. This it draws into itself, and on that account is the best means of purifying; for, on being repeatedly agitated in earthen pots it casts out the other things and the impurities. These things being rejected, in order that it may give up the gold, it is squeezed in prepared skins, through which, exuding like perspiration, it leaves the gold pure." It may be noted particularly that both these authors state that gold is the only substance that does not float, and, moreover, nowhere do we find any reference to silver combining with mercury, although Beckmann (Hist. of Inventions, Vol. I, p. 14) not only states that the above pa.s.sage from Pliny refers to silver, but in further error, attributes the origin of silver amalgamation of ores to the Spaniards in the Indies.

The Alchemists of the Middle Ages were well aware that silver would amalgamate with mercury. There is, however, difficulty in any conclusion that it was applied by them to separating silver or gold from ore. The involved gibberish in which most of their utterances was couched, obscures most of their reactions in any event. The School of Geber (Appendix B) held that all metals were a compound of "spiritual" mercury and sulphur, and they clearly amalgamated silver with mercury, and separated them by distillation. The _Probierbuchlein_ (1520?) describes a method of recovering silver from the cement used in parting gold and silver, by mixing the cement (silver chlorides) with quicksilver.

Agricola nowhere in this work mentions the treatment of silver ores by amalgamation, although he was familiar with Biringuccio (_De La Pirotechnia_), as he himself mentions in the Preface. This work, published at least ten years before _De Re Metallica_, contains the first comprehensive account of silver amalgamation. There is more than usual interest in the description, because, not only did it precede _De Re Metallica_, but it is also a specific explanation of the fundamental essentials of the Patio Process long before the date when the Spaniards could possibly have invented that process in Mexico. We quote Mr. A.

d.i.c.k's translation from Percy (Metallurgy of Silver and Gold, p. 560):

"He was certainly endowed with much useful and ingenious thought who invented the short method of extracting metal from the sweepings produced by those arts which have to do with gold and silver, every substance left in the refuse by smelters, and also the substance from certain ores themselves, without the labour of fusing, but by the sole means and virtue of mercury. To effect this, a large basin is first constructed of stone or timber and walled, into which is fitted a millstone made to turn like that of a mill. Into the hollow of this basin is placed matter containing gold (_della materia vra che tiene oro_), well ground in a mortar and afterward washed and dried; and, with the above-mentioned millstone, it is ground while being moistened with vinegar, or water, in which has been dissolved corrosive sublimate (_solimato_), verdigris (_verde rame_), and common salt. Over these materials is then put as much mercury as will cover them; they are then stirred for an hour or two, by turning the millstone, either by hand, or horse-power, according to the plan adopted, bearing in mind that the more the mercury and the materials are bruised together by the millstone, the more the mercury may be trusted to have taken up the substance which the materials contain. The mercury, in this condition, can then be separated from the earthy matter by a sieve, or by washing, and thus you will recover the auriferous mercury (_el vro mercurio_).

After this, by driving off the mercury by means of a flask (_i.e._, by heating in a retort or an alembic), or by pa.s.sing it through a bag, there will remain, at the bottom, the gold, silver, or copper, or whatever metal was placed in the basin under the millstone to be ground.

Having been desirous of knowing this secret, I gave to him who taught it to me a ring with a diamond worth 25 ducats; he also required me to give him the eighth part of any profit I might make by using it. This I wished to tell you, not that you should return the ducats to me for teaching you the secret, but in order that you should esteem it all the more and hold it dear."

In another part of the treatise Biringuccio states that washed (concentrated) ores may be ultimately reduced either by lead or mercury.

Concerning these silver concentrates he writes: "Afterward drenching them with vinegar in which has been put green copper (_i.e._, verdigris); or drenching them with water in which has been dissolved vitriol and green copper...." He next describes how this material should be ground with mercury. The question as to who was the inventor of silver amalgamation will probably never be cleared up. According to Ulloa (_Relacion Historica Del Viage a la America Meridional_, Madrid, 1748) Dom Pedro Fernandes De Velasco discovered the process in Mexico in 1566. The earliest technical account is that of Father Joseph De Acosta (_Historia Natural y Moral de las Indias_, Seville, 1590, English trans.

Edward Grimston, London, 1604, re-published by the Hakluyt Society, 1880). Acosta was born in 1540, and spent the years 1570 to 1585 in Peru, and 1586 in Mexico. It may be noted that Potosi was discovered in 1545. He states that refining silver with mercury was introduced at Potosi by Pedro Fernandes de Velasco from Mexico in 1571, and states (Grimston's Trans., Vol. I, p. 219): "... They put the powder of the metall into the vessels upon furnaces, whereas they anoint it and mortifie it with brine, putting to every fiftie quintalles of powder five quintalles of salt. And this they do for that the salt separates the earth and filth, to the end the quicksilver may the more easily draw the silver unto it. After, they put quicksilver into a piece of holland and presse it out upon the metall, which goes forth like a dewe, alwaies turning and stirring the metall, to the end it may be well incorporate.

Before the invention of these furnaces of fire, they did often mingle their metall with quicksilver in great troughes, letting it settle some daies, and did then mix it and stirre it againe, until they thought all the quicksilver were well incorporate with the silver, the which continued twentie daies and more, and at least nine daies." Frequent mention of the different methods of silver amalgamation is made by the Spanish writers subsequent to this time, the best account being that of Alonso Barba, a priest. Barba was a native of Lepe, in Andalusia, and followed his calling at various places in Peru from about 1600 to about 1630, and at one time held the Curacy of St. Bernard at Potosi. In 1640 he published at Madrid his _Arte de los Metales_, etc., in five books.

The first two books of this work were translated into English by the Earl of Sandwich, and published in London in 1674, under the t.i.tle "The First Book of the Art of Metals." This translation is equally wretched with those in French and German, as might be expected from the translators' total lack of technical understanding. Among the methods of silver amalgamation described by Barba is one which, upon later "discovery" at Virginia City, is now known as the "Washoe Process." None of the Spanish writers, so far as we know, make reference to Biringuccio's account, and the question arises whether the Patio Process was an importation from Europe or whether it was re-invented in Mexico.

While there is no direct evidence on the point, the presumption is in favour of the former.

The general introduction of the amalgamation of silver ores into Central Europe seems to have been very slow, and over 200 years elapsed after its adoption in Peru and Mexico before it received serious attention by the German Metallurgists. Ignaz Elder v. Born was the first to establish the process effectually in Europe, he having in 1784 erected a "quick-mill" at Gla.s.shutte, near Shemnitz. He published an elaborate account of a process which he claimed as his own, under the t.i.tle _Ueber das Anquicken der Gold und Silberhaltigen Erze_, Vienna, 1786. The only thing new in his process seems to have been mechanical agitation.

According to Born, a Spaniard named Don Juan de Corduba, in the year 1588, applied to the Court at Vienna offering to extract silver from ores with mercury. Various tests were carried out under the celebrated Lazarus Erckern, and although it appears that some vitriol and salt were used, the trials apparently failed, for Erckern concluded his report with the advice: "That their Lordships should not suffer any more expense to be thrown away upon this experiment." Born's work was translated into English by R. E. Raspe, under the t.i.tle--"Baron Inigo Born's New Process of Amalgamation, etc.," London, 1791. Some interest attaches to Raspe, in that he was not only the author of "Baron Munchausen," but was also the villain in Scott's "Antiquary." Raspe was a German Professor at Ca.s.sel, who fled to England to avoid arrest for theft. He worked at various mines in Cornwall, and in 1791 involved Sir John Sinclair in a fruitless mine, but disappeared before that was known. The incident was finally used by Sir Walter Scott in this novel.

[13] _Aurum in ea remanet purum_. This same error of a.s.suming squeezed amalgam to be pure gold occurs in Pliny; see previous footnote.

[14] George, Duke of Saxony, surnamed "The Bearded," was born 1471, and died 1539. He was chiefly known for his bitter opposition to the Reformation.

[15] The Julian Alps are a section east of the Carnic Alps and lie north of Trieste. The term Rhaetian Alps is applied to that section along the Swiss Italian Boundary, about north of Lake Como.

[16] Ancient Lusitania comprised Portugal and some neighbouring portions of Spain.

[17] Colchis, the traditional land of the Golden Fleece, lay between the Caucasus on the north, Armenia on the south, and the Black Sea on the west. If Agricola's account of the metallurgical purpose of the fleece is correct, then Jason must have had real cause for complaint as to the tangible results of his expedition. The fact that we hear nothing of the fleece after the day it was taken from the dragon would thus support Agricola's theory. Tons of ink have been expended during the past thirty centuries in explanations of what the fleece really was. These explanations range through the supernatural and metallurgical, but more recent writers have endeavoured to construct the journey of the Argonauts into an epic of the development of the Greek trade in gold with the Euxine. We will not attempt to traverse them from a metallurgical point of view further than to maintain that Agricola's explanation is as probable and equally as ingenious as any other, although Strabo (XI, 2, 19.) gives much the same view long before.

Alluvial mining--gold washing--being as old as the first glimmer of civilization, it is referred to, directly or indirectly, by a great majority of ancient writers, poets, historians, geographers, and naturalists. Early Egyptian inscriptions often refer to this industry, but from the point of view of technical methods the description by Pliny is practically the only one of interest, and in Pliny's chapter on the subject, alluvial is badly confused with vein mining. This pa.s.sage (x.x.xIII, 21) is as follows: "Gold is found in the world in three ways, to say nothing of that found in India by the ants, and in Scythia by the Griffins. The first is as gold dust found in streams, as, for instance, in the Tagus in Spain, in the Padus in Italy, in the Hebrus in Thracia, in the Pactolus in Asia, and in the Ganges in India; indeed, there is no gold found more perfect than this, as the current polishes it thoroughly by attrition.... Others by equal labour and greater expense bring rivers from the mountain heights, often a hundred miles, for the purpose of washing this debris. The ditches thus made are called _corrugi_, from our word _corrivatio_, I suppose; and these entail a thousand fresh labours. The fall must be steep, that the water may rush down from very high places, rather than flow gently. The ditches across the valleys are joined by aqueducts, and in other places, impa.s.sable rocks have to be cut away and forced to make room for troughs of hollowed-out logs. Those who cut the rocks are suspended by ropes, so that to those who watch them from a distance, the workmen seem not so much beasts as birds.

Hanging thus, they take the levels and trace the lines which the ditch is to take; and thus, where there is no place for man's footstep, streams are dragged by men. The water is vitiated for washing if the current of the stream carries mud with it. This kind of earth is called _urium_, hence these ditches are laid out to carry the water over beds of pebbles to avoid this _urium_. When they have reached the head of the fall, at the top of the mountain, reservoirs are excavated a couple of hundred feet long and wide, and about ten feet deep. In these reservoirs there are generally five gates left, about three feet square, so that when the reservoir is full, the gates are opened, and the torrent bursts forth with such violence that the rocks are hurled along. When they have reached the plain there is yet more labour. Trenches called _agogae_ are dug for the flow of the water. The bottoms of these are spread at regular intervals with _ulex_ to catch the gold. This _ulex_ is similar to rosemary, rough and p.r.i.c.kly. The sides, too, are closed in with planks and are suspended when crossing precipitous spots. The earth is carried to the sea and thus the shattered mountain is washed away and scattered; and this deposition of the earth in the sea has extended the sh.o.r.e of Spain.... The gold procured from _arrugiae_ does not require to be melted, but is already pure gold. It is found in lumps, in shafts as well, sometimes even exceeding ten _librae_ in weight. These lumps are called _palagae_ and _palacurnae_, while the small grains are called _baluce_. The Ulex is dried and burnt and the ashes are washed on a bed of gra.s.sy turf in order that the gold may settle thereon."

[19] _Carbunculus Carchedonius_--Carthaginian carbuncle. The German is given by Agricola in the _Interpretatio_ as _granat_, _i.e._, garnet.

[20] As the concentration of crushed tin ore has been exhaustively treated of already, the descriptions from here on probably refer entirely to alluvial tin.

[21] From a metallurgical point of view all of these operations are roasting. Even to-day, however, the expression "burning" tin is in use in some parts of Cornwall, and in former times it was general.

[22] There can be no doubt that these are mattes, as will develop in Book IX. The German term in the Glossary for _panes ex pyrite_ is _stein_, the same as the modern German for matte. Orpiment and realgar are the yellow and red a.r.s.enical sulphides. The _cadmia_ was no doubt the cobalt-a.r.s.enic minerals (see note on p. 112). The "solidified juices" were generally anything that could be expelled short of smelting, _i.e._, roasted off or leached out, as shown in note 4, p. 1; they embrace the sulphates, salts, sulphur, bitumen, and a.r.s.enical sulphides, etc. For further information on leaching out the sulphates, alum, etc., see note 10, p. 564.

BOOK IX.[1]

Since I have written of the varied work of preparing the ores, I will now write of the various methods of smelting them. Although those who burn, roast and calcine[2] the ore, take from it something which is mixed or combined with the metals; and those who crush it with stamps take away much; and those who wash, screen and sort it, take away still more; yet they cannot remove all which conceals the metal from the eye and renders it crude and unformed. Wherefore smelting is necessary, for by this means earths, solidified juices, and stones are separated from the metals so that they obtain their proper colour and become pure, and may be of great use to mankind in many ways. When the ore is smelted, those things which were mixed with the metal before it was melted are driven forth, because the metal is perfected by fire in this manner.

Since metalliferous ores differ greatly amongst themselves, first as to the metals which they contain, then as to the quant.i.ty of the metal which is in them, and then by the fact that some are rapidly melted by fire and others slowly, there are, therefore, many methods of smelting.

Constant practice has taught the smelters by which of these methods they can obtain the most metal from any one ore. Moreover, while sometimes there are many methods of smelting the same ore, by which an equal weight of metal is melted out, yet one is done at a greater cost and labour than the others. Ore is either melted with a furnace or without one; if smelted with a furnace the tap-hole is either temporarily closed or always open, and if smelted without a furnace, it is done either in pots or in trenches. But in order to make this matter clearer, I will describe each in detail, beginning with the buildings and the furnaces.

A wall which will be called the "second wall" is constructed of brick or stone, two feet and as many palms thick, in order that it may be strong enough to bear the weight. It is built fifteen feet high, and its length depends on the number of furnaces which are put in the works; there are usually six furnaces, rarely more, and often less. There are three furnace walls, a back one which is against the "second" wall, and two side ones, of which I will speak later. These should be made of natural stone, as this is more serviceable than burnt bricks, because bricks soon become defective and crumble away, when the smelter or his deputy chips off the accretions which adhere to the walls when the ore is smelted. Natural stone resists injury by the fire and lasts a long time, especially that which is soft and devoid of cracks; but, on the contrary, that which is hard and has many cracks is burst asunder by the fire and destroyed. For this reason, furnaces which are made of the latter are easily weakened by the fire, and when the accretions are chipped off they crumble to pieces. The front furnace wall should be made of brick, and there should be in the lower part a mouth three palms wide and one and a half feet high, when the hearth is completed. A hole slanting upward, three palms long, is made through the back furnace wall, at the height of a cubit, before the hearth has been prepared; through this hole and a hole one foot long in the "second" wall--as the back of this wall has an arch--is inserted a pipe of iron or bronze, in which are fixed the nozzles of the bellows. The whole of the front furnace wall is not more than five feet high, so that the ore may be conveniently put into the furnace, together with those things which the master needs for his work of smelting. Both the side walls of the furnace are six feet high, and the back one seven feet, and they are three palms thick. The interior of the furnace is five palms wide, six palms and a digit long, the width being measured by the s.p.a.ce which lies between the two side walls, and the length by the s.p.a.ce between the front and the back walls; however, the upper part of the furnace widens out somewhat.

[Ill.u.s.tration 357 (Blast Furnaces): A--Furnaces. B--Forehearths.]

There are two doors in the second wall if there are six furnaces, one of the doors being between the second and third furnaces and the other between the fourth and fifth furnaces. They are a cubit wide and six feet high, in order that the smelters may not have mishaps in coming and going. It is necessary to have a door to the right of the first furnace, and similarly one to the left of the last, whether the wall is longer or not. The second wall is carried further when the rooms for the cupellation furnaces, or any other building, adjoin the rooms for the blast furnaces, these buildings being only divided by a part.i.tion. The smelter, and the ones who attend to the first and the last furnaces, if they wish to look at the bellows or to do anything else, go out through the doors at the end of the wall, and the other people go through the other doors, which are the common ones. The furnaces are placed at a distance of six feet from one another, in order that the smelters and their a.s.sistants may more easily sustain the fierceness of the heat.

Inasmuch as the interior of each furnace is five palms wide and each is six feet distant from the other, and inasmuch as there is a s.p.a.ce of four feet three palms at the right side of the first furnace and as much at the left side of the last furnace, and there are to be six furnaces in one building, then it is necessary to make the second wall fifty-two feet long; because the total of the widths of all of the furnaces is seven and a half feet, the total of the s.p.a.ces between the furnaces is thirty feet, the s.p.a.ce on the outer sides of the first and last furnaces is nine feet and two palms, and the thickness of the two transverse walls is five feet, which make a total measurement of fifty-two feet.[3]