De Re Metallica Part 21

The third of this genus of machine is made of a pipe or pipes and a barrel. Above the uppermost pipe there is erected a wooden barrel, four feet high and three feet in diameter, bound with wooden hoops; it has a square blow-hole always open, which catches the breezes and guides them down either by a pipe into a conduit or by many pipes into the shaft. To the top of the upper pipe is attached a circular table as thick as the bottom of the barrel, but of a little less diameter, so that the barrel may be turned around on it; the pipe projects out of the table and is fixed in a round opening in the centre of the bottom of the barrel. To the end of the pipe a perpendicular axle is fixed which runs through the centre of the barrel into a hole in the cover, in which it is fastened, in the same way as at the bottom. Around this fixed axle and the table on the pipe, the movable barrel is easily turned by a zephyr, or much more by a wind, which govern the wing on it. This wing is made of thin boards and fixed to the upper part of the barrel on the side furthest away from the blow-hole; this, as I have said, is square and always open. The wind, from whatever quarter of the world it blows, drives the wing straight toward the opposite direction, in which way the barrel turns the blow-hole towards the wind itself; the blow-hole receives the wind, and it is guided down into the shaft by means of the conduit or pipes.

[Ill.u.s.tration 204 (Ventilation Fans): A--Drum. B--Box-shaped casing.

C--Blow-hole. D--Second hole. E--Conduit. F--Axle. G--Lever of axle.

H--Rods.]

The second genus of blowing machine is made with fans, and is likewise varied and of many forms, for the fans are either fitted to a windla.s.s barrel or to an axle. If to an axle, they are either contained in a hollow drum, which is made of two wheels and a number of boards joining them together, or else in a box-shaped casing. The drum is stationary and closed on the sides, except for round holes of such size that the axle may turn in them; it has two square blow-holes, of which the upper one receives the air, while the lower one empties into the conduit through which the air is led down the shaft. The ends of the axle, which project on each side of the drum, are supported by forked posts or hollowed beams plated with thick iron; one end of the axle has a crank, while in the other end are fixed four rods with thick heavy ends, so that they weight the axle, and when turned, make it p.r.o.ne to motion as it revolves. And so, when the workman turns the axle by the crank, the fans, the description of which I will give a little later, draw in the air by the blow-hole, and force it through the other blow-hole which leads to the conduit, and through this conduit the air penetrates into the shaft.

[Ill.u.s.tration 205 (Ventilation Fans): A--Box-shaped casing placed on the ground. B--Its blow-hole. C--Its axle with fans. D--Crank of the axle.

E--Rods of same. F--Casing set on timbers. G--Sails which the axle has outside the casing.]

The one with the box-shaped casing is furnished with just the same things as the drum, but the drum is far superior to the box; for the fans so fill the drum that they almost touch it on every side, and drive into the conduit all the air that has been acc.u.mulated; but they cannot thus fill the box-shaped casing, on account of its angles, into which the air partly retreats; therefore it cannot be as useful as the drum.

The kind with a box-shaped casing is not only placed on the ground, but is also set up on timbers like a windmill, and its axle, in place of a crank, has four sails outside, like the sails of a windmill. When these are struck by the wind they turn the axle, and in this way its fans--which are placed within the casing--drive the air through the blow-hole and the conduit into the shaft. Although this machine has no need of men whom it is necessary to pay to work the crank, still when the sky is devoid of wind, as it often is, the machine does not turn, and it is therefore less suitable than the others for ventilating a shaft.

[Ill.u.s.tration 206 (Ventilation Fans): A--Hollow drum. B--Its blow-hole.

C--Axle with fans. D--Drum which is made of rundles. E--Lower axle.

F--Its toothed wheel. G--Water wheel.]

In the kind where the fans are fixed to an axle, there is generally a hollow stationary drum at one end of the axle, and on the other end is fixed a drum made of rundles. This rundle drum is turned by the toothed wheel of a lower axle, which is itself turned by a wheel whose buckets receive the impetus of water. If the locality supplies an abundance of water this machine is most useful, because to turn the crank does not need men who require pay, and because it forces air without cessation through the conduit into the shaft.

[Ill.u.s.tration 207 (Ventilation Fans): A--First kind of fan. B--Second kind of fan. C--Third kind of fan. D--Quadrangular part of axle.

E--Round part of same. F--Crank.]

Of the fans which are fixed on to an axle contained in a drum or box, there are three sorts. The first sort is made of thin boards of such length and width as the height and width of the drum or box require; the second sort is made of boards of the same width, but shorter, to which are bound long thin blades of poplar or some other flexible wood; the third sort has boards like the last, to which are bound double and triple rows of goose feathers. This last is less used than the second, which in turn is less used than the first. The boards of the fan are mortised into the quadrangular parts of the barrel axle.

[Ill.u.s.tration 208 (Bellows for mine ventilation): A--Smaller part of shaft. B--Square conduit. C--Bellows. D--Larger part of shaft.]

Blowing machines of the third genus, which are no less varied and of no fewer forms than those of the second 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 vapours. In the latter case, when the bellows is opened it draws the vapours from the conduits through its blow-hole and sucks these vapours into itself; in the former case, when it is compressed, it drives the air through its nozzle into the conduits or pipes. They are compressed either by a man, or by a horse or by water-power; if by a man, the lower board of a large bellows is fixed to the timbers above the conduit which projects out of the shaft, and so placed that when the blast is blown through the conduit, its nozzle is set in the conduit. When it is desired to suck out heavy or pestilential vapours, the blow-hole of the bellows is fitted all round the mouth of the conduit. Fixed to the upper bellows board is a lever which couples with another running downward from a little axle, into which it is mortised so that it may remain immovable; the iron journals of this little axle revolve in openings of upright posts; and so when the workman pulls down the lever the upper board of the bellows is raised, and at the same time the flap of the blow-hole is dragged open by the force of the wind. If the nozzle of the bellows is enclosed in the conduit it draws pure air into itself, but if its blow-hole is fitted all round the mouth of the conduit it exhausts the heavy and pestilential vapours out of the conduit and thus from the shaft, even if it is one hundred and twenty feet deep. A stone placed on the upper board of the bellows depresses it and then the flap of the blow-hole is closed. The bellows, by the first method, blows fresh air into the conduit through its nozzle, and by the second method blows out through the nozzle the heavy and pestilential vapours which have been collected.

In this latter case fresh air enters through the larger part of the shaft, and the miners getting the benefit of it can sustain their toil.

A certain smaller part of the shaft which forms a kind of estuary, requires to be part.i.tioned off from the other larger part by uninterrupted lagging, which reaches from the top of the shaft to the bottom; through this part the long but narrow conduit reaches down nearly to the bottom of the shaft.

[Ill.u.s.tration 209 (Bellows for mine ventilation): A--Tunnel. B--Pipe.

C--Nozzle of double bellows.]

When no shaft has been sunk to such depth as to meet a tunnel driven far into a mountain, these machines should be built in such a manner that the workman can move them about. Close by the drains of the tunnel through which the water flows away, wooden pipes should be placed and joined tightly together in such a manner that they can hold the air; these should reach from the mouth of the tunnel to its furthest end. At the mouth of the tunnel the bellows should be so placed that through its nozzle it can blow its acc.u.mulated blasts into the pipes or the conduit; since one blast always drives forward another, they penetrate into the tunnel and change the air, whereby the miners are enabled to continue their work.

[Ill.u.s.tration 211 (Bellows for mine ventilation): A--Machine first described. B--This workman, treading with his feet, is compressing the bellows. C--Bellows without nozzles. D--Hole by which heavy vapours or blasts are blown out. E--Conduits. F--Tunnel. G--Second machine described. H--Wooden wheel. I--Its steps. K--Bars. L--Hole in same wheel. M--Pole. N--Third machine described. O--Upright axle. P--Its toothed drum. Q--Horizontal axle. R--Its drum which is made of rundles.]

If heavy vapours need to be drawn off from the tunnels, generally three double or triple bellows, without nozzles and closed in the forepart, are placed upon benches. A workman compresses them by treading with his feet, just as persons compress those bellows of the organs which give out varied and sweet sounds in churches. These heavy vapours are thus drawn along the air-pipes and through the blow-hole of the lower bellows board, and are expelled through the blow-hole of the upper bellows board into the open air, or into some shaft or drift. This blow-hole has a flap-valve, which the noxious blast opens, as often as it pa.s.ses out.

Since one volume of air constantly rushes in to take the place of another which has been drawn out by the bellows, not only is the heavy air drawn out of a tunnel as great as 1,200 feet long, or even longer, but also the wholesome air is naturally drawn in through that part of the tunnel which is open outside the conduits. In this way the air is changed, and the miners are enabled to carry on the work they have begun. If machines of this kind had not been invented, it would be necessary for miners to drive two tunnels into a mountain, and continually, at every two hundred feet at most, to sink a shaft from the upper tunnel to the lower one, that the air pa.s.sing into the one, and descending by the shafts into the other, would be kept fresh for the miners; this could not be done without great expense.

There are two different machines for operating, by means of horses, the above described bellows. The first of these machines has on its axle a wooden wheel, the rim of which is covered all the way round by steps; a horse is kept continually within bars, like those within which horses are held to be shod with iron, and by treading these steps with its feet it turns the wheel, together with the axle; the cams on the axle press down the sweeps which compress the bellows. The way the instrument is made which raises the bellows again, and also the benches on which the bellows rest, I will explain more clearly in Book IX. Each bellows, if it draws heavy vapours out of a tunnel, blows them out of the hole in the upper board; if they are drawn out of a shaft, it blows them out through its nozzle. The wheel has a round hole, which is transfixed with a pole when the machine needs to be stopped.

The second machine has two axles; the upright one is turned by a horse, and its toothed drum turns a drum made of rundles on a horizontal axle; in other respects this machine is like the last. Here, also, the nozzles of the bellows placed in the conduits blow a blast into the shaft or tunnel.

[Ill.u.s.tration 212 (Ventilating with Damp Cloth): A--Tunnel. B--Linen cloth.]

In the same way that this last machine can refresh the heavy air of a shaft or tunnel, so also could the old system of ventilating by the constant shaking of linen cloths, which Pliny[20] has explained; the air not only grows heavier with the depth of a shaft, of which fact he has made mention, but also with the length of a tunnel.

[Ill.u.s.tration 213 (Descent into Mines): A--Descending into the shaft by ladders. B--By sitting on a stick. C--By sitting on the dirt.

D--Descending by steps cut in the rock.]

The climbing machines of miners are ladders, fixed to one side of the shaft, and these reach either to the tunnel or to the bottom of the shaft. I need not describe how they are made, because they are used everywhere, and need not so much skill in their construction as care in fixing them. However, miners go down into mines not only by the steps of ladders, but they are also lowered into them while sitting on a stick or a wicker basket, fastened to the rope of one of the three drawing machines which I described at first. Further, when the shafts are much inclined, miners and other workmen sit in the dirt which surrounds their loins and slide down in the same way that boys do in winter-time when the water on some hillside has congealed with the cold, and to prevent themselves from falling, one arm is wound about a rope, the upper end of which is fastened to a beam at the mouth of the shaft, and the lower end to a stake fixed in the bottom of the shaft. In these three ways miners descend into the shafts. A fourth way may be mentioned which is employed when men and horses go down to the underground machines and come up again, that is by inclined shafts which are twisted like a screw and have steps cut in the rock, as I have already described.

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 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; the man who does not follow this advice will suffer much ill-health, especially when he reaches old age. 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, and the disease which the Greeks call [Greek: asthma]. If the dust has corrosive qualities, it eats away the lungs, and implants consumption in the body; hence in the mines of the Carpathian Mountains women are found who have married seven husbands, all of whom this terrible consumption has carried off to a premature death. At Altenberg in Meissen there is found in the mines black _pompholyx_, which eats wounds and ulcers to the bone; this also corrodes iron, for which reason the keys of their sheds are made of wood. Further, there is a certain kind of _cadmia_[21] which eats away the feet of the workmen when they have become wet, and similarly their hands, and injures their lungs and eyes. 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. Not dissimilarly, among the Romans[22] the makers of vermilion took precautions against breathing its fatal dust.

Stagnant air, both that which remains in a shaft and that which remains in a tunnel, produces a difficulty in breathing; the remedies for this evil are the ventilating machines which I have explained above. 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 not unlike _pompholyx_,[23] which clings to the upper part of the walls in the works in which ore is smelted. 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 neighbouring 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 pa.s.s away.

There are also times when a reckoning has to be made with Orcus,[24] for some metalliferous localities, though such are rare, spontaneously produce poison and exhale pestilential vapour, as is also the case with some openings in the ore, though these more often contain the noxious fumes. In the towns of the plains of Bohemia there are some caverns which, at certain seasons of the year, emit pungent vapours which put out lights and kill the miners if they linger too long in them. Pliny, too, has left a record that when wells are sunk, the sulphurous or aluminous vapours which arise kill the well-diggers, and it is a test of this danger if a burning lamp which has been let down is extinguished.

In such cases a second well is dug to the right or left, as an air-shaft, which draws off these noxious vapours. On the plains they construct bellows which draw up these noxious vapours and remedy this evil; these I have described before.

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, and to cover so securely with planks the sumps at the bottom of the shafts, that the planks cannot be moved nor the men fall into the water; wherefore the foreman must carefully execute his own work. 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.

In fact, when in olden days Rammelsberg, in Goslar, sank down, so many men were crushed in the ruins that in one day, the records tell us, about 400 women were robbed of their husbands. And eleven years ago, part of the mountain of Altenberg, which had been excavated, became loose and sank, and suddenly crushed six miners; it also swallowed up a hut and one mother and her little boy. But this generally occurs in those mountains which contain _venae c.u.mulatae_. Therefore, miners should leave numerous arches under the mountains which need support, or provide underpinning. Falling pieces of rock also injure their limbs, and to prevent this from happening, miners should protect the shafts, tunnels, and drifts.

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

This animal is, as Solinus[25] writes, very small and like a spider in shape; it is called _solifuga_, because it shuns (_fugit_) the light (_solem_). It is very common in silver mines; it creeps un.o.bserved and brings destruction upon those who imprudently sit on it. But, as the same writer tells us, springs of warm and salubrious waters gush out in certain places, which neutralise the venom inserted by the ants.

In some of our mines, however, though in very few, there are other pernicious pests. These are demons of ferocious aspect, about which I have spoken in my book _De Animantibus Subterraneis_. Demons of this kind are expelled and put to flight by prayer and fasting.[26]

Some of these evils, as well as certain other things, are the reason why pits are occasionally abandoned. But the first and princ.i.p.al cause is that they do not yield metal, or if, for some fathoms, they do bear metal they become barren in depth. The second cause is the quant.i.ty of water which flows in; sometimes the miners can neither divert this water into the tunnels, since tunnels cannot be driven so far into the mountains, or they cannot draw it out with machines because the shafts are too deep; or if they could draw it out with machines, they do not use them, the reason undoubtedly being that the expenditure is greater than the profits of a moderately poor vein. The third cause is the noxious air, which the owners sometimes cannot overcome either by skill or expenditure, for which reason the digging is sometimes abandoned, not only of shafts, but also of tunnels. The fourth cause is the poison produced in particular places, if it is not in our power either completely to remove it or to moderate its effects. This is the reason why the caverns in the Plain known as Laurentius[27] used not to be worked, though they were not deficient in silver. The fifth cause are the fierce and murderous demons, for if they cannot be expelled, no one escapes from them. The sixth cause is that the underpinnings become loosened and collapse, and a fall of the mountain usually follows; the underpinnings are then only restored when the vein is very rich in metal. The seventh cause is military operations. Shafts and tunnels should not be re-opened unless we are quite certain of the reasons why the miners have deserted them, because we ought not to believe that our ancestors were so indolent and spiritless as to desert mines which could have been carried on with profit. Indeed, in our own days, not a few miners, persuaded by old women's tales, have re-opened deserted shafts and lost their time and trouble. Therefore, to prevent future generations from being led to act in such a way, it is advisable to set down in writing the reason why the digging of each shaft or tunnel has been abandoned, just as it is agreed was once done at Freiberg, when the shafts were deserted on account of the great inrush of water.

END OF BOOK VI.

FOOTNOTES:

[1] This Book is devoted in the main to winding, ventilating, and pumping machinery. Their mechanical principles are very old. The block and pulley, the windla.s.s, the use of water-wheels, the transmission of power through shafts and gear-wheels, chain-pumps, piston-pumps with valves, were all known to the Greeks and Romans, and possibly earlier.

Machines involving these principles were described by Ctesibius, an Alexandrian of 250 B.C., by Archimedes (287-212 B.C.), and by Vitruvius (1st Century B.C.) As to how far these machines were applied to mining by the Ancients we have but little evidence, and this largely in connection with handling water. Diodorus Siculus (1st Century B.C.) referring to the Spanish mines, says (Book V.): "Sometimes at great depths they meet great rivers underground, but by art give check to the violence of the streams, for by cutting trenches they divert the current, and being sure to gain what they aim at when they have begun, they never leave off till they have finished it. And they admirably pump out the water with those instruments called Egyptian pumps, invented by Archimedes, the Syracusan, when he was in Egypt. By these, with constant pumping by turns they throw up the water to the mouth of the pit and thus drain the mine; for this engine is so ingeniously contrived that a vast quant.i.ty of water is strangely and with little labour cast out."

Strabo (63 B.C.-24 A.D., III., 2, 9), also referring to Spanish mines, quoting from Posidonius (about 100 B.C.), says: "He compares with these (the Athenians) the activity and diligence of the t.u.r.detani, who are in the habit of cutting tortuous and deep tunnels, and draining the streams which they frequently encounter by means of Egyptian screws."

(Hamilton's Tran., Vol. I., p. 221). The "Egyptian screw" was Archimedes' screw, and was thus called because much used by the Egyptians for irrigation. Pliny (x.x.xIII., 31) also says, in speaking of the Spanish silver-lead mines: "The mountain has been excavated for a distance of 1,500 paces, and along this distance there are water-carriers standing by torch-light night and day steadily baling the water (thus) making quite a river." The re-opening of the mines at Rio Tinto in the middle of the 18th Century disclosed old Roman stopes, in which were found several water-wheels. These were about 15 feet in diameter, lifting the water by the reverse arrangement to an overshot water-wheel. A wooden Archimedian screw was also found in the neighbourhood. (Nash, The Rio Tinto Mine, its History and Romance, London, 1904).

Until early in the 18th Century, water formed the limiting factor in the depth of mines. To the great devotion to this water problem we owe the invention of the steam engine. In 1705 Newcomen--no doubt inspired by Savery's unsuccessful attempt--invented his engine, and installed the first one on a colliery at Wolverhampton, in Staffords.h.i.+re. With its success, a new era was opened to the miner, to be yet further extended by Watt's improvements sixty years later. It should be a matter of satisfaction to mining engineers that not only was the steam engine the handiwork of their profession, but that another mining engineer, Stephenson, in his effort to further the advance of his calling, invented the locomotive.

[2] While these particular tools serve the same purpose as the "gad" and the "moil," the latter are not fitted with handles, and we have, therefore, not felt justified in adopting these terms, but have given a literal rendering of the Latin.

The Latin and old German terms for these tools were:--

First Iron tool = _Ferramentum primum_ = _Bergeisen_.

Second " = " _secundum_ = _Rutzeisen_.

Third " = " _tertium_ = _Sumpffeisen_.

Fourth " = " _quartum_ = _Fimmel_.

Wedge = _Cuneus_ = _Keil_.

Iron block = _Lamina_ = _Plotz_.

Iron plate = _Bractea_ = _Feder_.