Georgius Agricola’s De Re Metallica is a sixteenth-century Latin treatise on mining and metallurgy, organized into twelve books that move from the case for mining as an honorable calling through the geology of veins, mine surveying and law, timbering and ventilation, the machinery of hoisting and drainage, assaying, ore-dressing, and the smelting and refining of metals. Agricola wrote it in Saxony, in the mining districts whose practices it records; woodcuts of machines and furnaces illustrate it throughout, and Latin and German technical vocabulary accompany the text. A short appended work treats the creatures found underground.
The book’s central claim is announced at the outset and defended at length: mining is not a sordid or fortuitous trade but an ancient, necessary, and honorable art, older than agriculture because no one ever farmed without metal tools, and deserving the same learned treatment that husbandry had long received from Greek and Latin writers. Everything that follows is built on that premise—the technical books are the proof of the art’s difficulty and dignity.
From the Miner’s Character to the Refining Fire
The Title Page, Privilege, and Dedication
The volume opens with a title page advertising twelve books on mining offices, instruments, machines, and everything touching metals, illustrated with figures and giving Latin and German names, together with an appended book on subterranean creatures and full indexes. A French royal privilege follows, granted at Paris on 18 February 1553 by Henry, King of France, to the Basle booksellers Jérôme Froben and Nicolas l’Évêque. The two merchants had recovered several previously unseen works, among them Agricola’s collected opera, and feared rival printers would reprint them and rob them of their outlay; the King accordingly forbids any other printer or seller to touch the book for six years from the completion of printing, on pain of confiscation and arbitrary fine.
Agricola’s dedication goes to the Dukes of Saxony and Landgraves of Thuringia, and especially to Maurice, Archmarshal and Elector of the Holy Roman Empire, and his brother Augustus. He confesses that, like Columella pondering husbandry, he has often feared his life would fail before he could master the magnitude of mining, so many arts does it require. Yet the subject is most ancient and most necessary: agriculture may be the oldest science, but mining is older or coeval, since no mortal ever farmed without instruments, and instruments are made of metals. One mine often yields more profit than many fields. Husbandry, he notes, has over fifty Greek writers and more than ten Latin ones; mining has only Pliny, who gives very few methods, and among the Greeks only Strato of Lampsacus, perhaps the poet Philo, and the comic Pherecrates, who brought metal-workers or men condemned to the mines on stage. In German there are two confused books on metallic matter and veins, one reportedly by Pandulfus Angius, and a partial work by Calbus Fribergius; Vannoccio Biringuccio of Siena treated smelting and separating in Italian, and it was Franciscus Badoarius, Venetian patrician, who gave Agricola that book, promising it while he followed King Ferdinand at Marienberg as Venetian envoy.
The Alchemists and the Plan of the Work
A long roll of alchemists follows—Osthanes, Hermes, Zosimus of Alexandria writing to his sister Theosebia, Democritus, Maria Judaea, Cleopatra, the virgin Taphnutia, Raymundus Lullius, Arnaldus of Villanova, and many more, all in prose except Johannes Aurelius Augurellus of Ariminum, who alone wrote in verse. All are obscure, naming things by alien and self-invented terms. They claim to corrupt base metals, reduce them to prime matter, and supply what is lacking to make gold and silver; Agricola declines to judge whether they can, observing that many assert success yet no one is recorded as enriched by the art. A second sort merely tints base metal gold or silver, a disguise fire strips away; a third secretly encloses gold or silver in coal and pretends to make it from auripigment or white lead—both hated and punished capitally. Since no writer has fully recorded mining, he has written these twelve books: the first refutes objections and describes the mining man; the second and third treat veins, fibres, and joints; the fourth measuring and offices; the fifth digging and the surveyor’s art; the sixth instruments and machines; the seventh testing; the eighth burning, crushing, washing, and roasting; the ninth smelting; the tenth separating silver from gold and lead from silver and gold; the eleventh separating silver from copper. A Latin poem praising Agricola, Germany’s metals, and the miner’s labours and piety closes the preliminaries.
In Defence of Mining
Book I opens by conceding that many hold mining fortuitous and sordid, needing labour but no art; Agricola disagrees, since the miner must know the positions of mountains and valleys, veins, fibres, joints, earths, juices, gems, stones, marbles, and metals, all subterranean work, and the testing and preparing of materials, which differ for each metal. He grants that some ore sellers and buyers are fraudulent, but a prudent, skilled man can inspect the vein himself before buying or selling; often the deceiver deceives himself, since a vein may prove richer than expected, so the “deceived” party profits and the “deceiver” loses. Magistrates judge disputes equitably, so a good miner cheats no one and a bad one cannot easily cheat or go unpunished. Mining profit harms no one; unlike the usurer’s immoderate interest, the miner’s gain is great, abundant, and not sordid. Critics object that criminals were once condemned to the mines and slaves dug veins; by that logic agriculture, architecture, and medicine would also be dishonourable, yet agriculture and medicine are counted honourable arts. He distinguishes miners, labourers, skilled experts, and those who invest—among them kings, princes, republics, and honourable citizens—citing Thucydides, whom the Athenians put over the Thasian mines. Maximilian Caesar enrolled Conrad among the counts called nobles, a man once poorest while working in the Sneberg mines, hence called “the poor,” who later grew rich from the Firsti mines in Lotharingia; King Vladislaus placed Turfius, a Cracow citizen enriched by Hungarian mines, in his assembly of Barons. The mining plebs is not vile: inured to nightly vigils and labour, they have huge bodily hardness and easily endure military labours, and experts in war set them over both urban and rural plebs. Comparing gains—usurer, warrior, merchant, farmer, miner—usury is hateful and plunder impious; mining’s honesty surpasses the merchant’s profit, is no less good than the farmer’s, and far more fruitful. Of the ten greatest goods, finding great money in good manner is what a diligent man can most easily achieve through mining.
Lifting Machines of Book VI
The third machine in the sequence of lifting devices tires its workers less than its predecessors, though it is slower, as all drum-driven machines tend to be; it raises loads to a depth of 180 feet. Its upright axle turns in two iron bearings, the lower set into a cross-timber and the upper into a beam. Below sits a wheel of thick joined planks; above it a toothed drum, which in turn drives a second drum built of spindles. A hauling rope winds around this axle. Two workers grip a pole fixed between two upright posts and push the tread-wheels backward with their feet, reversing the machine each time a vessel is drawn full and overturned so that the second vessel can be raised. A key identifies the parts from axle to tread-wheels.
The fourth machine lifts loads six times greater than the first two. Sixteen timbers, fifteen feet long and a foot thick and wide, are clamped at the top and spread at the bottom, their lower ends set into ground-sills and braced by oblique timbers to enclose a round area about fifty feet across. At its centre a pit ten feet deep is dug and lined with stakes and small timbers so the earth cannot collapse; a timber with a hardened iron bearing sits at the pit bottom, and a matching bearing is fixed at the top between two uprights. The square axle, forty feet long, carries four oblique timbers whose tops support doubled cross-timbers, and the drum has three wheels seven feet apart with spindles running between them, winding two hauling ropes. The building is roofed with shingles except on the side facing the shaft. Two rows of cross-timbers rest on posts and carry two hollowed beams reaching almost from the drum to the shaft; near the drum a wooden axle turns in iron rings, carrying pulleys over which each rope runs to an iron hook on its vessel. From the head of one doubled timber hangs a seat for the driver, fitted with an iron pin, chain and steelyard, so that two horses can draw the machine either way—four if the shaft is deep. After a vessel is drawn, a worker throws in a hook and overturns it.
The fifth machine borrows partly from the largest machine and partly from the third: like the third it is turned by horses and has two axles, an upright one with a toothed drum set lower down in a pit, and a horizontal one with a spindled drum. Like the largest it has two drums on the horizontal axle, smaller and able to draw vessels from a shaft only forty feet deep. A hook pressed against one drum holds the machine when leather sacks of rock or earth are drawn and overturned, or water is poured out; for this machine lifts both dry and wet loads, and timbers tied to its hauling chain are also lowered into the shaft. The hook projects from a timber hanging by a chain from a movable timber held in the claws of an upright; from the other end hangs a long timber, and from it a short seat where the worker presses down, then wedges a board beneath so the hook grips the drum so strongly that sparks often fly. The hanging timber is pierced with holes to adjust the chain, and a board roof keeps dripping water off the drum, since a wet drum makes the hook hold less. Near the other drum a chain hangs from a post, its last ring holding a three-foot iron hook that fits a ring at the bottom of a vessel or sack so the water can be poured out.
Ventilation and the Diseases of Miners
When a shaft is very deep with no tunnel or connecting passage, or a tunnel runs so long that no shaft reaches it, the air cannot be thinned and grows thick and hard to breathe; miners are sometimes suffocated and their lamps extinguished. Hence machines are needed—the Greeks call them pneumatikai, the Latins spiritales—of three genera. The first drives a blast of wind into the shaft in three species. In the first, three beams are placed over a shaft no tunnel reaches, their ends held by pointed stakes driven into the ground; the middle beam carries three forms enclosing transverse beams on the right, left and middle, with boards joined alternately to make four corners and as many hollows that catch winds from every direction, covered above by a circular lid so the rising winds are carried back into the shaft’s four openings. Where the wind blows through the top, no lid is needed. The second species leads the blast down a long channel formed of four boards joined as often as the shaft’s depth requires, joints smeared with fat, glutinous earth; the channel either rises out of the shaft like a quadrangular funnel to catch the blast more easily, or boards are fixed opposite the wind to drive it in. The third species uses a wooden vessel with a spirit-opening, pipe, circle, little axis, hole and wing: wherever the wind blows, the wing is struck and turns the vessel’s opening into the wind, which is caught and led by the pipe into the long channel or pipes into the shaft.
A drum and a box are then compared: the box’s parts match the drum’s, but the drum surpasses it, since flabella can occupy the drum so as almost to touch it everywhere and drive all the air into the channel, while air recedes into the box’s corners. The box may stand on the ground or on beams like a windmill, with four wings that turn the axle and its flabella; but when the sky is still, as often happens, it does not turn, so it suits ventilation less well. Flabella enclosed in an axle are usually made of hollow drum and spindles.
A fan with a double nostril draws healthy air in through one nostril and breathes out heavy or pestilent vapours through the other; since healthy air enters the greater part of the shaft, miners can endure the labour, the smaller part at the shaft’s mouth being separated by boards running from top to bottom, through which a long narrow channel descends almost to the shaft’s throat.
Washing Gold Sands by Cloth and Basin
The treatise turns from the extraction of ore to the recovery of fine gold from loose sands, and the first device is a homely one: a green cloth laid over a horsehair weave whose countless small knots, lightly shaved so they stand proud, catch the tiny particles of gold that the water carries over them. The knotted cloth is spread, the knots shown enlarged, and the vessel in which it is finally rinsed is set out in the figures. From there the washing moves to the ore-head itself, where sands mixed with gold are worked in a small basin, a lake, or a channel. The basin is hollowed from a squared oak trunk or a thick plank, open at the back, three feet long and a foot and a half wide, its hollow shaped like the narrow part of a trough and turned toward the head; two long handles let the washer draw it to and fro against the current, cleansing the wash-water whether it bore gold particles or the black pebbles from which white lead is made.
The Italian Method
Italians who come to the German mountains for gold wash the river sands in a long, low lake hollowed from a single tree, rounded within and without, open on one side and closed on the other. Sunk in the channel so that the water does not fall in but gently stirs the sand, it is agitated with a rounded wooden rutrum; the particles and carbuncles float out with the light sand, and the open part is closed with a rounded board lower than the lake’s hollow. The gold, settling with a little heavy sand, is washed in the channel, gathered into leather bags, and carried off.
The Eight Ways of Washing, and the Ditch
The author promises to set out the various ways of washing gold-bearing sand and of separating the black pebbles that yield white lead, noting eight usual methods, two of them recently invented. Metallic material is torn by water from veins and fibers and scattered far and wide, though sometimes the veins themselves are dilated and consist of it; the former is dug with broad hoes, the latter with pointed ones, and a tool like a duck’s beak serves for material free of pebbles. Where waters abound and the valleys are gentle, streams are led into long sloping ditches so the percolating water runs swiftly. The dug material is thrown in together with turf some six feet high, built of moss, roots, small trees, and earth; the heavy sand and black pebbles settle at the bottom while the light moss and roots are swept away. The washers, their feet in high leather boots, stand in the ditch, fork out the roots with seven-pronged wooden forks, and drive the black pebbles to the head. After four weeks of this labor they remove the pebbles, agitating the sand in the waters until only the pebbles remain, then wash them in a small basin with a wooden batillum, returning to the same work until the material fails or the streams can no longer be led in.
Basins, Channels, and the First Smelting Furnace
The small basin is hollowed from one trunk, five feet long, three-quarters of a foot high, six digits wide, set sloping; beneath it stands a vessel of twisted fir branches or a second basin where the minute pebbles settle, and some place a squared channel beneath, or a transverse channel that discharges either openly into a vessel or, closed and perforated in the middle, into a ditch below, so the water falls straight down as if from a whirlwind. With the washing done, the text passes to the furnaces. Earth is dried in the sun, thrown on a hurdle of withes so fine dust falls through while clods roll off, carted to the workshop, sieved, and the dust mixed with charcoal dust and moistened in a covered pit. Two parts charcoal dust to one of crushed earth, raked and watered, makes the mud that coats the inside of a new furnace; an old furnace must first have its adhering cadmia cut away and its broken cavities filled with stone or brick. The workman climbs a ladder, a board fastened to it for leaning, and smooths the mud with a long wooden spatula, taking care that the bronze pipe’s mouth does not protrude. He then stamps the hearth solid with a round pestle, slopes it toward the basin, cuts the basin with a curved iron blade, and blocks the mouth with charcoal held in place by a stick while the coals are thrown in.
Iron, Quicksilver, and Lead
Iron is finished in eight or ten hours; the master uses a pole when the bellows blow too sharply or when he adds vein-stone and charcoal or draws off slag, which flows through the channel into a wheel and axle that compresses the bellows. The hanging mass of two or three hundredweight is thrown down and struck with wooden mallets to knock off slag, then cut with sharp iron into four, five, or six pieces and formed into rectangular masses called meres, canthi, and bacilla; a boy pours water on the glowing iron, and the mass left in the basin is hard iron for crossbow-bolt heads. Vein that is burnt or hard demands a larger, taller furnace, the fragments no bigger than a nut thrown in with charcoal by workmen ascending steps at the side. Quicksilver is made several ways: in pots with bell-shaped lids whose nostrils feed clay cucurbits, sealed with clay and heated; or in a vaulted chamber where the ore is cooked and the quicksilver, impatient of heat and loving cold, flies to the green leaves placed within, whence it is shaken down and collected. Lead is made in a dry trench sprinkled with charcoal powder, where split logs are laid on the ore and the molten lead drips into the trench; because burnt wood fouls it, some dig the trench on a slope with a basin beneath, paved with flat stones whose joints are smeared with mud and charcoal powder, or use channels of pitch-pine down which the lead flows pure.
The Silver Works and the Making of Cakes
The work of separating silver from copper reaches its most demanding stage in a workshop where a long wooden-handled tool, two and a half feet in length, stirs the purifying mixture. A workman pours the molten blend with a bronze ladle into a bronze basin, adding copper fragments from which the second cake is to be melted. As the material begins to flow, silver foam is thrown in again; coals follow, then lead without delay. This labour repeats until thirty cakes have been made, consuming nine or at most ten hours, and any workman who exceeds thirty cakes is paid separately for each additional thirty. Once the copper-and-lead mixture enters the basin, water is poured gradually onto its upper part, and a split, hollowed wooden uncus—a finger and a half thick, its straight part two palms long and two digits wide—is thrust into the still-liquid cake. After the cake cools, the uncus is enclosed by a chain lowered from the crane’s tongue into an iron ring six digits wide, and the cake is lifted from the basin and returned to its place. Re-melted copper and lead exude a little dross and much silver foam, which does not cohere but slips away like the remnants of barley from which beer is made; a white-grey pompholyx clings to the wall and partition above, spodos to the sides.
The Furnaces and the Arithmetic of Separation
The text sets out the furnaces: a slow furnace for re-melting dross, a furnace where copper is mixed with lead, an opening, two bronze basins, a ladle, the uncus, split wood, and the crane’s tongue with its chain. Then come the calculations. If the silver portion is moderate, well and good; if it is large—say two pounds or two and a half—the overseer adds three hundredweights of lead to a hundredweight of copper, each hundredweight of lead carrying a third or a third and a half-ounce of silver, so that three cakes are made containing three parts copper and nine hundredweights of lead. When the lead is separated, it loses seven hundredweights; the silver that remains in the cakes is reckoned down to fractions of a drachma. If the silver portion is so small it cannot usefully be separated, the copper must first be re-cooked in another furnace, vaulted with crude bricks and resembling the kiln in which lead is separated from silver, its basin made from ash, with an opening at the front from which the re-cooked copper flows into two basins. A door on the left lets beech logs be brought in. Thirty-eight hundredweights are re-cooked together until each hundredweight of residual copper retains a third and a half-ounce of silver; the master weighs what has been abstracted, runs it into the basin beneath the furnace, and makes cakes from it, consuming fourteen hours. The residue, with a set weight of lead added, is cooked again in the first furnace, cakes are made, and silver is separated; the abstracted material is cooked and re-cooked until the residue turns red and caldarium copper is made from it. Forty hundredweights of tawny, red, or caldarium copper go into the second furnace at minimum.
The Glass Furnaces of Book XII
The final book turns to glass. Three-chambered furnaces are described: the second furnace’s square opening, a palm high and wide, passes heat into a third, rectangular furnace eight feet long and six wide, built of two chambers. The lower chamber has openings for inserting wood into a hearth on its floor, and oblong receptacles on each side for clay vessels; the upper chamber holds oblong vessels in which finished glass wares cool gradually, since rapid cooling bursts them. A labelled key marks the arch, the openings, the bellied pots, the receptacles, and the cooling vessels. Furnaces are built of crude sun-dried bricks made from earth that does not liquefy or crumble in fire, cleansed of stones and beaten with rods, with the same earth as mortar. The glass mass, made and broken in the first furnace, is re-melted in the second. Pots are heated gently so moisture exhales, then fiercely until dried and reddened; the glassmaker grasps them with tongs and, if uncracked, places them in the second furnace filled with fragments. All windows are blocked with clay and bricks except two small ones—through one the glassmaker inspects and receives glass with a pipe, in the other a pipe is kept warm. Brass, bronze, or iron pipes three feet long are used, with a marble slab before the windows.
The Glassmaker’s Craft and the Author’s Testimony
The longer the fragments are re-melted, the purer and less spotted the product; those who melt only one night make inferior glass to those who re-melt day and night, and two days and nights yield the best. Goodness lies not only in the material but in the melting. The glassmaker tests by dipping a pipe and turning it: a viscous, glutinous, globular substance adheres; he takes what he needs, presses and rolls it on marble, inflates it through the pipe like a bladder, moving the pipe from mouth to jaw lest flame be drawn in, then shapes it by turning or in a hollow bronze instrument, forming cups and vessels by reheating, blowing, pressing, and enlarging, widening the bottom on marble, using a second pipe, cutting the mouth with shears, adding feet and handles, gilding and painting, and finally placing it in the oblong clay vessel to cool. Boys alternately feed the fires. Glassmakers make cups, bowls, pitchers, flasks, dishes, platters, mirrors, and figures of animals, trees, and ships. Agricola records that he saw many such admirable works at Venice over two years, especially on Ascension Day when wares were brought for sale to Murano, where the most famous glass workshops are; he saw them when he met Andrea Naugerio together with Francesco Asulano at Naugerio’s house there.
The Case for an Honorable Trade
Agricola knows the objections and meets them head-on. Critics say miners are cheats, that condemned criminals once dug the veins, that the work is filthy and its profits usurious. His answer runs through the social scale: kings, princes, and republics have invested in mines; the Roman senate would not have called Cincinnatus from his farm if farming disgraced a man; the Emperor Maximilian raised a poor Sneberg laborer to the ranks of the nobility after the mines made him rich. If slave labor dishonors mining, he notes dryly, it would dishonor agriculture and medicine too. The miner’s gain, unlike the usurer’s, harms no one. He is careful, though, to distinguish the honest operator from the swindler who salts coal with hidden gold — a fraud he says is punished capitally — and he insists that a skilled man can read a vein for himself before buying or selling, so that the deceiver often ends up the loser.
The Owner’s Eye and the Miner’s God
Running through the practical books is a moral psychology of work. The perfect miner first worships God and then attends to his business, because providence favors those who know and take care. The owner must live at the mine, descend into it, study the veins, and sometimes take up a tool himself — not to exhaust himself but to stir the workers, since, as a barbarian told Xenophon, the master’s eye fattens the horse. Diligent workers are praised and rewarded, the negligent dismissed. Agricola also thinks in terms of risk: a man who stakes everything on one vein either grows very rich or loses all, while one who shares expense across a dozen veins rarely loses his outlay, since a single rich strike repays the rest. Xenophon’s scheme for the Athenians to search for new veins in common is prudent, he grants, but belongs only to free and opulent cities; under kings and tyrants no one dares such expense without permission.
Air, Law, and the Order of the Mine
Two of the book’s most striking stretches concern things invisible: the law that governs a claim and the air that keeps men alive. The ancient rite of measuring a vein has a discoverer place two fingers on the windlass and swear that the vein is his, invoking God and all the gods, on pain of his head and hand failing their office; the mine-master then measures out the head area and portions for the prince, his wife, his master of horse, his cupbearer, his chamberlain, and himself. The ceremony survives, Agricola notes, though the arithmetic has changed. As for air, he observes that in spring and summer the outside air pours down the higher shaft and out the lower, and reverses in autumn and winter, shifting within about a fortnight at the turn of the seasons. Where no shaft reaches a long tunnel, the air thickens until lamps go out and men suffocate, and so he describes the pneumatikai, the “spiritual machines” — wind-catching boards, funneled channels, revolving vanes, and great bellows — that drive a blast into the workings. His account of timbering is equally attentive to fear as well as physics: the boards that separate the ladder-way keep loosened rock from falling and, he says, make the descent less terrifying.
The Test and the Fire
The later books turn to judgment. Assaying is a discipline of small weights and patient steps: gold-bearing material is worked with quicksilver and washed, silver ore is fused with lead in an ash cup until the lead exhales and the silver’s weight reveals the ore’s richness, copper is tested without lead because copper flies off, tin ore is melted down through a pierced charcoal block, quicksilver ore is cooked in a sealed vessel and its vapor caught in a cooled flask. The washing of gold sands gets eight methods, two of them recent inventions, down to the horsehair cloth whose knotted nap traps the finest particles. And the smelting books describe furnaces lined with mud mixed from charcoal dust and earth, hearths stamped solid with pestles, iron drawn out in masses of two or three hundredweight and struck with wooden mallets before the great hammer cuts it, and finally the “strong water” and powders that part gold from silver. The book ends where the metal does: in the refining workshop, among the hearths and lids and bellows where silver is separated from lead and copper, the long labor of the treatise closing in fire.
A Manual That Outlived Its Mines
De Re Metallica preserves a whole industrial world — the Saxon and Bohemian and Carpathian districts, the shafts and adits, the water wheels and treadwheels, the customs of the mining courts — at the moment before those practices began to change. Its woodcuts are among the most detailed records we have of early modern machinery, and its Latin coinages and German glosses make it a dictionary of a trade as much as a description of one. The book’s confidence that a technical subject deserves the same eloquence and system as poetry or husbandry was itself an argument, and it is the reason the work was consulted, translated, and mined for centuries afterward by engineers and historians alike.
