Many persons hold the opinion that the metal industries are fortuitous and that the occupation is one of sordid toil, and altogether a kind of business requiring not so much skill as labor.  But as for myself, when I reflect carefully upon its special points one by one, it appears to be far otherwise.  For a miner must have the greatest skill in his work, that he may know first of all what mountain or hill, what valley or plain, can be prospected most profitably, or what he should leave alone; moreover, he must understand the veins, stringers [smaller veins that intersect with larger veins] and seams in the rocks.  Then he must be thoroughly familiar with the many and varied species of earths, juices [substance which dissolves when put into liquid], gems, stones, marbles, rocks, metals, and compounds.

He must also have a complete knowledge of the method of making all underground works.  Lastly, there are various systems of assaying substances and of preparing them for smelting; and here again there are many altogether diverse methods.  For there is one method for gold and silver, another for copper, another for quicksilver, another for iron, another for lead, and even tin and bismuth are treated differently from lead.  Although the evaporation of juices is an art apparently quite distinct from metallurgy, yet they ought not to be considered separately, in as much as these juices are also often dug out of the ground solidified, or they are produced from certain kinds of earth and stones which the miners dig up, and some of the juices are not themselves devoid of metals.  Again, their treatment is not simple, since there is one method for common salt, another for soda, another for alum, another for vitriol [green vitriol, or iron sulfate], another for sulfur, and another for bitumen.

Furthermore, there are many arts and sciences of which a miner should not be ignorant.

• First there is Philosophy, that he may discern the origin, cause, and nature of subterranean things; for then he will be able to dig out the veins easily and advantageously, and to obtain more abundant results from his mining.

• Secondly, there is Medicine, that he may be able to look after his diggers and other workmen, that they do not meet with those diseases to which they are more liable than workmen in other occupations, or if they do meet with them, that he himself may be able to heal them or may see that the doctors do so.

• Thirdly follows Astronomy, that he may know the divisions of the heavens and from them judge the direction of the veins.

• Fourthly, there is the science of Surveying that he may be able to estimate how deep a shaft should be sunk to reach the tunnel which is being driven to it, and to determine the limits and boundaries in these workings, especially in depth.

• Fifthly, his knowledge of Arithmetical Science should be such that he may calculate the cost to be incurred in the machinery and the working of the mine.

• Sixthly, his learning must comprise Architecture, that he himself may construct the various machines and timber work required underground, or that he may be able to explain the method of the construction to others.

• Next, he must have knowledge of Drawing, that he can draw plans of his machinery.

• Lastly, there is the Law, especially that dealing with metals, that he may claim his own rights, that he may undertake the duty of giving others his opinion on legal matters, that he may not take another man's property and so make trouble for himself, and that he may fulfill his obligations to others according to the law.

Book II.

... Now a miner, before he begins to mine the veins, must consider seven things, namely:--the situation, the conditions, the water, the roads, the climate, the right of ownership, and the neighbors.  There are four kinds of situations--mountain, hill, valley, and plain.  Of these four, the first two are the most easily mined, because in them tunnels can be driven to drain off the water, which often makes mining operations very laborious, if it does not stop them altogether.  The last two kinds of ground are more troublesome, especially because tunnels cannot be driven in such places....

With regard to the conditions of the locality the miner should not contemplate mining without considering whether the place be covered with trees or is bare.  If it be a wooded place, he who digs there has this advantage, besides others, that there will be an abundant supply of wood for his underground timbering, his machinery, buildings, smelting, and other necessities....

The miner should next consider the locality, as to whether it has a perpetual supply of running water, or whether it is always devoid of water except when a torrent supplied by rains flows down from the summits of the mountains....  [T]o convey a constant supply of water by artificial means to mines where Nature has denied it access, or to convey the ore to the stream, increases the expense greatly, in proportion to the distance the mines are away from the river.

The miner also should consider whether the roads from the neighboring regions to the mines are good or bad, short or long....

Then, the miner should make careful and thorough investigation concerning the lord of the locality, whether he be a just and good man or a tyrant, for the latter oppresses men by force of his authority, and seizes their possessions for himself but the former governs justly and lawfully and serves the common good....

The miner should try to obtain a mine, to which access is not difficult, in a mountainous region, gently sloping, wooded, healthy, safe, and not far distant from a river or stream by means of which he may convey his mining products to be washed and smelted....

Book III.

... [N]ow I come to the third book, which is about veins and stringers, and the seams in the rocks.  The term "vein" is sometimes used to indicate canales in the earth ... I now attach a second significance to these words, for by them I mean to designate any mineral substances which the earth keeps hidden within her own deep receptacles....

--from Agricola's De Ortu et Causis

If a vein which cuts through another principal one obliquely be the harder of the two, it penetrates right through it, just as a wedge of beech or iron can be driven through soft wood by means of a tool.  If it be softer, the principal vein either drags the soft one with it for a distance of three feet, or perhaps one, two, three, or several fathoms, or else throws it forward along the principal vein; but this latter happens very rarely.  But that the vein which cuts the principal one is the same vein on both sides, is shown by its having the same character in its foot walls and hanging walls.

Sometimes venae profundae join one with another, and from two or more outcropping veins, one is formed; or from two which do not outcrop one is made, if they are not far distant from each other, and the one dips into the other, or if each dips toward the other, and they thus join when they have descended in depth.  In exactly the same way, out of three or more veins, one may be formed in depth....

Furthermore, one vein may be split and divided into parts by some hard rock resembling a beak, or stringers in soft rock may sunder the vein and make two or more.  These sometimes join together again and sometimes remain divided....

A great number of miners consider that the best veins in depth are those which run from the ... east to the ... west, through a mountain slope which inclines to the north....  Therefore they devote all their energies to those veins, and give very little or nothing to those whose heads ... rise toward the south or west....  And they say that from veins of this kind, since the sun's rays draw out the metallic material, very little metal is gained.  But in this matter the actual experience of the miners who thus judge of the veins does not always agree with their opinions, nor is their reasoning sound....

It may be denied that the heat of the sun draws the metallic material out of these veins; for though it draws up vapors from the surface of the ground, the rays of the sun do not penetrate right down to the depths; because the air of a tunnel which is covered and enveloped by solid earth to the depth of only two fathoms is cold in summer, for the intermediate earth holds in check the fore of the sun....  Therefore it is unlikely that the sun draws out from within the earth the metallic bodies.  Indeed, it cannot even dry the moisture of many places abounding in veins, because they are protected and shaded by the trees....

Book V.

In this book I will ... explain the principles of underground mining and the art of surveying....  And so I will describe first of all the digging of shafts, tunnels, and drifts on venae profundae; next I will discuss the good indications shown by canales, by the materials which are dug out, and by the rocks; then I will speak of the tools by which veins and rocks are broken down and excavated; the method by which fire shatters the hard veins; and further, off the machines with which water is drawn from the shafts and air is forced into deep shafts and long tunnels, for digging is impeded by the inrush of the former or the failure of the latter; next I will deal with the two kinds of shafts, and with the making of them and of tunnels; and finally, I will describe the method of mining venae dilatatae, venae cumulatae, and stringers.

Now when a miner discovers a vena profunda he begins sinking a shaft and above it sets up a windlass, and builds a shed over the shaft to prevent the rain from falling in, lest the men who turn the windlass be numbed by the cold or troubled by the rain  The windlass men also place their barrows in it, and the  miners store their iron tools and other implements therein.  Next to the shaft-house another house is built, where the mine foreman and the other workmen dwell, and in which are stored the ore and other things which are dug out....

Now a shaft is dug, usually two fathoms long, two-thirds of a fathom wide, and thirteen fathoms deep....  A tunnel is a subterranean ditch driven lengthwise, and is nearly twice as high as it is broad, and wide enough that workmen and others may be able to pass and carry their loads....

Let us now consider the metallic material which is found in the canales....  As soon as a miner who searches for veins discovers pure metal or minerals, or rich metallic material, or a great abundance of material which is poor in metal, let him sink a shaft on the spot without any delay....

Gold, silver, copper, and quicksilver are often found native [pure]; less often iron and bismuth; almost never tin and lead....

I now come to the mode of working, which is varied and complex, for in some places they dig crumbling ore, in others hard ore, in others a harder ore, and in others the hardest kind of ore....

Miners dig out crumbling ore with the pick alone....  As for the hardest kind of metal-bearing vein, which in a measure resists iron tools ... they break it with fires....

While the heated veins and rock are giving forth a fetid vapor and the shafts or tunnels are emitting fumes, the miners and other workmen do not go down in the mines lest the stench affect their health or actually kill them.....

It often happens that a rush of water or sometimes stagnant air hinders the mining; for this reason miners pay the greatest attention to these matters, just as much as to the digging, or they should do so.  The water of the veins and stringers and especially of vacant workings, must be drained out through the shafts and tunnels.  Air, indeed, becomes stagnant both in the tunnels and in shafts; in a deep shaft, if it be by itself, this occurs if it is neither reached by a tunnel nor connected by a drift with another shaft; this occurs in a tunnel if it has been driven too far into a mountain and no shaft has yet been sunk deep enough to meet it; in neither case can the air move or circulate.  For this reason the vapors become heavy and resemble mist, and they smell of moldiness, like a vault or some underground chamber which has been completely closed for many years.  This suffices to prevent miners from continuing their work for long in these places, even if the mine is full of silver or gold, or if they do continue, they cannot breathe freely and they have headaches; this more often happens if they work in these places in great numbers, and bring many lamps, which then supply them with a feeble light, because the foul air from both lamps and men make the vapors still more heavy.

A small quantity of water is drawn from the shafts by machines of different kinds which men turn or work.  If so great a quantity has flowed into one shaft as greatly to impede mining, another shaft is sunk some fathoms distant from the first, and thus in one of them work and labor are carried on without hindrance, and the water is drained into the other, which is sunk lower than the level of the water in the first one; then by these machines or by those worked by horses, the water is drawn up into the drain and flows out of the shaft-house or the mouth of the nearest tunnel.  But when into the shaft of one mine, which is sunk more deeply, there flows all the water of all the neighboring mines, not only from that vein in which the shaft is sunk, but also from other veins, then it becomes necessary for a large sump to be made to collect the water; from this sump the water is drained by machines which draw it through pipes, or by ox-hides....

Air is driven into the extremities of deep shafts and long tunnels by powerful blowing machines....  The outer air flows spontaneously into the caverns of the earth, and when it can pass through them comes out again....

Now shafts ... are supported in various ways.  If the vein is hard ... the shaft does not require much timbering, but timbers are placed at intervals....

When a very deep shaft, whether vertical or inclined, is supported by joined timbers, then, since they are sometimes of bad material and a fall is threatened, for the sake of greater firmness three or four pairs of strong end posts are placed between these....  If a vertical shaft is a very deep one, planks are laid upon the timbers by the side of the ladders and fixed on to the timbers, in order that the men who are going up or down may sit or stand upon them and rest when they are tired.  To prevent danger to the shovelers from rocks which, after being drawn up from so deep a shaft fall down again, a little above the bottom of the shaft small rough sticks are placed close together on the timbers, in such a way as to cover the whole space of the shaft except the ladder-way....  [A]nd so the shovelers and other workmen, as it were hiding beneath this structure, remain perfectly safe in the shaft.

In mines on one vein there are driven one, two, or sometimes three or more tunnels, always one above the other.  If the vein is solid and hard ... no part of the tunnel needs support, beyond that which is required at the mouth...; if the vein is soft, ... the tunnel requires frequent strong timbering....

I have completed one part of this book, and now come to the other, in which I will deal with the art of surveying....

Each method of surveying depends on the measuring of triangles.   A small triangle should be laid out, and from it calculations must be made regarding a larger one.  Most particular care must be taken that we do not deviate at all from a correct measuring; for if, at the beginning, we are drawn by carelessness into a slight error, this at the end will produce great errors....

....I will now speak first of all, of the iron tools with which veins and rocks are broken, then of the buckets into which the lumps of earth, rock, metal, and other excavated materials are thrown, in order that they may be drawn, conveyed or carried out.  Also, I will speak of the water vessels and drains, then of the machines of different kinds, and lastly of the maladies of miners.  And while all these matters are being described accurately, many methods of work will be explained....

Hauling machines are of varied and diverse forms, some of them being made with great skill, and if I am not mistaken, they were unknown to the Ancients.  They have been invented in order that water may be drawn from the depths of the earth to which no tunnels reach, and also the excavated material from shafts which are likewise not connected with a tunnel, or if so, only with very long ones....

Water is either hoisted or pumped out of shafts.  It is hoisted up after being poured into buckets or water-bags....  Water is drawn up also by chains of dippers, or by suction pumps, or by "rag and chain" pumps....

I will now explain ... the pump which draws, by means of pistons, water which has been raised by suction.  Of these there are seven varieties, which though they differ from one another in structure, nevertheless confer the same benefits upon miners, though some to a greater degree than others.

The first pump is made as follows.  Over the sump is placed a flooring, through which a pipe--or two lengths of pipe, one of which is joined into the other--are let down to the bottom of the sump; they are fastened with pointed iron clamps driven in straight on both sides, so that the pipes may remain fixed.  The lower end of the lower pipe is enclosed in a trunk two feet deep; this trunk, hollow like the pipe, stands at the bottom of the sump, but the lower opening of it is blocked with a round piece of wood; the trunk has perforations round about, through which water flows into it.  If there is one length of pipe, then the upper part of the trunk which has been hollowed out there is enclosed a box of iron, copper, or brass, one palm deep, but without a bottom, and a rounded valve so tightly closes it that the water, which has been drawn up by suction, cannot run back; but if there are two lengths of pipe, the box is enclosed in the lower pipe at the point of junction.  An opening or a spout in the upper pipe reaches to the drain of the tunnel.  Thus the workman, eager at his labor, standing on the flooring boards, pushes the piston down into the pipe and draws it out again.  At the top of the piston-rod is a hand-bar and the bottom is fixed in a shoe; this is the name given to the leather covering, which is almost cone-shaped, for it is so stitched that it is tight at the lower end, where it is fixed to the piston-rod which it surrounds, but in the upper end where it draws the water it is wide open.  Or else an iron disk one digit thick is used, or one of wood six digits thick, each of which is far superior to the shoe.  The disk is fixed by an iron key which penetrates through the bottom of the piston-rod, or it is screwed on to the rod; it is round, with its upper part protected by a cover, and has five or six openings, either round or oval, which taken together present a star-like appearance; the disc has the same diameter as the inside of the pipe, so that it can be just drawn up and down in it.  When the workman draws the piston up, the water which has passed in at the openings of the disk, whose cover is then closed, is raised to the hole or little spout, through which it flows away; then the valve of the box opens, and the water which has passed into the trunk is drawn up by the suction and rises into the pipe; but when the workman pushes down the piston, the valve closes and allows the disk again to draw in the water....

I will now speak of ventilating machines....

These devices are of three genera.  The first receives and diverts into the shaft the blowing of the wind....

The second genus of blowing machine is made with fans....

Blowing machines of the third genus ... are made with bellows, for by its blasts the shafts and tunnels are not only furnished with air through conduits or pipes, but they can also be cleared by suction of their heavy and pestilential vapors....

It remains for me to speak of the ailments and accidents of miners, and of the methods by which they can guard against these, for we should always devote more care to the maintaining our health, that we may freely perform our bodily functions, than to making profits.  Of the illnesses, some affect the joints, others attack the lungs, some the eyes, and finally some are fatal to men.

Where water in shafts is abundant and very cold, it frequently injures the limbs, for cold is harmful to the sinews.  To meet this, miners should make themselves sufficiently high boots of rawhide, which protect their legs from the cold water....  On the other hand, some mines are so dry that they are entirely devoid of water, and this dryness causes the workmen even greater harm, for the dust which is stirred and beaten up by digging penetrates into the windpipe and lungs, and produces difficulty in breathing....  If the dust has corrosive qualities, it eats away the lungs, and implants consumption in the body....  Therefore, for their digging they should make for themselves not only boots of rawhide, but gloves long enough to reach to the elbow, and they should fasten loose veils over their faces; the dust will then neither be drawn through these into their windpipes and lungs, nor will it fly into their eyes....

Stagnant air, both that which remains in a shaft and that which remains in a tunnel, produces a difficulty in breathing....  There is another illness even more destructive, which soon brings death to men who work in those shafts or levels or tunnels in which the hard rock is broken by fire.  Here the air is infected with poison, since large and small veins and seams in the rocks exhale some subtle poison from the minerals, which is driven out by the fire, and this poison itself is raised with the smoke....  If this poison cannot escape from the ground, but falls down into the pools and floats on their surface, it often causes danger, for if at any time the water is disturbed through a stone or anything else, these fumes rise again from the pools and thus overcome the men, by being drawn in with their breath; this is even much worse if the fumes of the fire have not yet all escaped.  The bodies of living creatures who are infected with this poison generally swell immediately and lose all movement and feeling, and they die without pain; men even in the act of climbing from the shafts by the steps of ladders fall back into the shafts when the poison overtakes them, because their hands do not perform their office, and seem to them to be round and spherical, and likewise their feet.  If by good fortune the injured ones escape these evils, for a little while they are pale and look like dead men.  At such times, no one should descend into the mine or into the neighboring mines, or if he is in them he should come out quickly.  Prudent and skilled miners burn the piles of wood on Friday, towards evening, and they do not descend into the shafts nor enter the tunnels again before Monday, and in the meantime the poisonous fumes pass away....

Further, sometimes workmen slipping from the ladders into the shafts break their arms, legs, or necks, or fall into the sumps and are drowned; often, indeed, the negligence of the foreman is to blame, for it is his special work both to fix the ladders so firmly to the timbers that they cannot break away, that the planks cannot be moved nor the men fall into the water....  Moreover, he must not set the entrance of the shaft-house toward the north wind, lest in winter the ladders freeze with cold, for when this happens the men's hands become stiff and slippery with cold, and cannot perform their office of holding.  The men, too, must be careful that, even if none of these things happen, they do not fall through their own carelessness.

Mountains, too, slide down and men are crushed in their fall and perish....

The venomous ant which exists in Sardinia is not found in our mines....

In some of our mines, however, though in very few, there are other pernicious pests.  These are demons of ferocious aspect....  Demons of this kind are expelled and put to flight by prayer and fasting.