De Re Metallica Part 20

D--Piston rod. E--Short piece of wood. F--Drain. G--This man is diverting the water which is flowing out of the drain, to prevent it from flowing into the trenches which are being dug.]

The third pump is not unlike the one just described, but in place of one upright, posts are erected with holes at the top, and in these holes the ends of an axle revolve. To the middle of this axle are fixed two wooden bars, to the end of one of which is fixed the piston, and to the end of the other a heavy piece of wood, but short, so that it can pa.s.s between the two posts and may move backward and forward. When the workman pushes this piece of wood, the piston is drawn out of the pipe; when it returns by its own weight, the piston is pushed in. In this way, the water which the pipe contains is drawn through the openings in the disc and emptied by the piston through the spout into the drain. There are some who place a hand-bar underneath in place of the short piece of wood.

This pump, as also the last before described, is less generally used among miners than the others.

[Ill.u.s.tration 180 (Duplex suction Pumps): A--Box. B--Lower part of box.

C--Upper part of same. D--Clamps. E--Pipes below the box. F--Column pipe fixed above the box. G--Iron axle. H--Piston-rods. I--Washers to protect the bearings. K--Leathers. L--Eyes in the axle. M--Rods whose ends are weighted with lumps of lead. N--Crank. (_This plate is unlettered in the first edition but corrected in those later._)]

The fourth kind is not a simple pump but a duplex one. It is made as follows. A rectangular block of beechwood, five feet long, two and a half feet wide, and one and a half feet thick, is cut in two and hollowed out wide and deep enough so that an iron axle with cranks can revolve in it. The axle is placed between the two halves of this box, and the first part of the axle, which is in contact with the wood, is round and the straight end forms a journal. Then the axle is bent down the depth of a foot and again bent so as to continue straight, and at this point a round piston-rod hangs from it; next it is bent up as far as it was bent down; then it continues a little way straight again, and then it is bent up a foot and again continues straight, at which point a second round piston-rod is hung from it; afterward it is bent down the same distance as it was bent up the last time; the other end of it, which also acts as a journal, is straight. This part which protrudes through the wood is protected by two iron washers in the shape of discs, to which are fastened two leather washers of the same shape and size, in order to prevent the water which is drawn into the box from gus.h.i.+ng out.

These discs are around the axle; one of them is inside the box and the other outside. Beyond this, the end of the axle is square and has two eyes, in which are fixed two iron rods, and to their ends are weighted lumps of lead, so that the axle may have a greater propensity to revolve; this axle can easily be turned when its end has been mortised in a crank. The upper part of the box is the shallower one, and the lower part the deeper; the upper part is bored out once straight down through the middle, the diameter of the opening being the same as the outside diameter of the column pipe; the lower box has, side by side, two apertures also bored straight down; these are for two pipes, the s.p.a.ce of whose openings therefore is twice as great as that of the upper part; this lower part of the box is placed upon the two pipes, which are fitted into it at their upper ends, and the lower ends of these pipes penetrate into trunks which stand in the sump. These trunks have perforations through which the water flows into them. The iron axle is placed in the inside of the box, then the two iron piston-rods which hang from it are let down through the two pipes to the depth of a foot.

Each piston has a screw at its lower end which holds a thick iron plate, shaped like a disc and full of openings, covered with a leather, and similarly to the other pump it has a round valve in a little box. Then the upper part of the box is placed upon the lower one and properly fitted to it on every side, and where they join they are bound by wide thick iron plates, and held with small wide iron wedges, which are driven in and are fastened with clamps. The first length of column pipe is fixed into the upper part of the box, and another length of pipe extends it, and a third again extends this one, and so on, another extending on another, until the uppermost one reaches the drain of the tunnel. When the crank worker turns the axle, the pistons in turn draw the water through their discs; since this is done quickly, and since the area of openings of the two pipes over which the box is set, is twice as large as the opening of the column pipe which rises from the box, and since the pistons do not lift the water far up, the impetus of the water from the lower pipes forces it to rise and flow out of the column pipe into the drain of the tunnel. Since a wooden box frequently cracks open, it is better to make it of lead or copper or bra.s.s.

[Ill.u.s.tration 182 (Suction Pumps): A--Tappets of piston-rods. B--Cams of the barrel. C--Square upper parts of piston-rods. D--Lower rounded parts of piston-rods. E--Cross-beams. F--Pipes. G--Apertures of pipes.

H--Trough. (Fifth kind of pump--see p. 181).]

The fifth kind of pump is still less simple, for it is composed of two or three pumps whose pistons are raised by a machine turned by men, for each piston-rod has a tappet which is raised, each in succession, by two cams on a barrel; two or four strong men turn it. When the pistons descend into the pipes their discs draw the water; when they are raised these force the water out through the pipes. The upper part of each of these piston-rods, which is half a foot square, is held in a slot in a cross-beam; the lower part, which drops down into the pipes, is made of another piece of wood and is round. Each of these three pumps is composed of two lengths of pipe fixed to the shaft timbers. This machine draws the water higher, as much as twenty-four feet. If the diameter of the pipes is large, only two pumps are made; if smaller, three, so that by either method the volume of water is the same. This also must be understood regarding the other machines and their pipes.

Since these pumps are composed of two lengths of pipe, the little iron box having the iron valve which I described before, is not enclosed in a trunk, but is in the lower length of pipe, at that point where it joins the upper one; thus the rounded part of the piston-rod is only as long as the upper length of pipe; but I will presently explain this more clearly.

[Ill.u.s.tration 183 (Suction Pumps): A--Water-wheel. B--Axle. C--Trunk on which the lowest pipe stands. D--Basket surrounding trunk. (Sixth kind of pump--see p. 184.)]

The sixth kind of pump would be just the same as the fifth were it not that it has an axle instead of a barrel, turned not by men but by a water-wheel, which is revolved by the force of water striking its buckets. Since water-power far exceeds human strength, this machine draws water through its pipes by discs out of a shaft more than one hundred feet deep. The bottom of the lowest pipe, set in the sump, not only of this pump but also of the others, is generally enclosed in a basket made of wicker-work, to prevent wood shavings and other things being sucked in. (See p. 183.)

[Ill.u.s.tration 185 (Suction Pumps): A--shaft. B--Bottom pump. C--First tank. D--Second pump. E--Second tank. F--Third pump. G--Trough. H--The iron set in the axle. I--First pump rod. K--Second pump rod. L--Third pump rod. M--First piston rod. N--Second piston rod. O--Third piston rod. P--Little axles. Q--"Claws."]

The seventh kind of pump, invented ten years ago, which is the most ingenious, durable, and useful of all, can be made without much expense.

It is composed of several pumps, which do not, like those last described, go down into the shaft together, but of which one is below the other, for if there are three, as is generally the case, the lower one lifts the water of the sump and pours it out into the first tank; the second pump lifts again from that tank into a second tank, and the third pump lifts it into the drain of the tunnel. A wheel fifteen feet high raises the piston-rods of all these pumps at the same time and causes them to drop together. The wheel is made to revolve by paddles, turned by the force of a stream which has been diverted to the mountain.

The spokes of the water-wheel are mortised in an axle six feet long and one foot thick, each end of which is surrounded by an iron band, but in one end there is fixed an iron journal; to the other end is attached an iron like this journal in its posterior part, which is a digit thick and as wide as the end of the axle itself. Then the iron extends horizontally, being rounded and about three digits in diameter, for the length of a foot, and serves as a journal; thence, it bends to a height of a foot in a curve, like the horn of the moon, after which it again extends straight out for one foot; thus it comes about that this last straight portion, as it revolves in an orbit becomes alternately a foot higher and a foot lower than the first straight part. From this round iron crank there hangs the first flat pump-rod, for the crank is fixed in a perforation in the upper end of this flat pump-rod just as the iron key of the first set of "claws" is fixed into the lower end. In order to prevent the pump-rod from slipping off it, as it could easily do, and that it may be taken off when necessary, its opening is wider than the corresponding part of the crank, and it is fastened on both sides by iron keys. To prevent friction, the ends of the pump-rods are protected by iron plates or intervening leathers. This first pump-rod is about twelve feet long, the other two are twenty-six feet, and each is a palm wide and three digits thick. The sides of each pump-rod are covered and protected by iron plates, which are held on by iron screws, so that a part which has received damage can be repaired. In the "claws" is set a small round axle, a foot and a half long and two palms thick. The ends are encircled by iron bands to prevent the iron journals which revolve in the iron bearings of the wood from slipping out of it.[15] From this little axle the wooden "claws" extend two feet, with a width and thickness of six digits; they are three palms distant from each other, and both the inner and outer sides are covered with iron plates. Two rounded iron keys two digits thick are immovably fixed into the claws.

The one of these keys perforates the lower end of the first pump-rod, and the upper end of the second pump-rod which is held fast. The other key, which is likewise immovable, perforates the iron end of the first piston-rod, which is bent in a curve and is immovable. Each such piston-rod is thirteen feet long and three digits thick, and descends into the first pipe of each pump to such depth that its disc nearly reaches the valve-box. When it descends into the pipe, the water, penetrating through the openings of the disc, raises the leather, and when the piston-rod is raised the water presses down the leather, and this supports its weight; then the valve closes the box as a door closes an entrance. The pipes are joined by two iron bands, one palm wide, one outside the other, but the inner one is sharp all round that it may fit into each pipe and hold them together. Although at the present time pipes lack the inner band, still they have nipples by which they are joined together, for the lower end of the upper one holds the upper end of the lower one, each being hewn away for a length of seven digits, the former inside, the latter outside, so that the one can fit into the other. When the piston-rod descends into the first pipe, that valve which I have described is closed; when the piston-rod is raised, the valve is opened so that the water can run in through the perforations.

Each one of such pumps is composed of two lengths of pipe, each of which is twelve feet long, and the inside diameter is seven digits. The lower one is placed in the sump of the shaft, or in a tank, and its lower end is blocked by a round piece of wood, above which there are six perforations around the pipe through which the water flows into it. The upper part of the upper pipe has a notch one foot deep and a palm wide, through which the water flows away into a tank or trough. Each tank is two feet long and one foot wide and deep. There is the same number of axles, "claws," and rods of each kind as there are pumps; if there are three pumps, there are only two tanks, because the sump of the shaft and the drain of the tunnel take the place of two. The following is the way this machine draws water from a shaft. The wheel being turned raises the first pump-rod, and the pump-rod raises the first "claw," and thus also the second pump-rod, and the first piston-rod; then the second pump-rod raises the second "claw," and thus the third pump-rod and the second piston-rod; then the third pump-rod raises the third "claw" and the third piston-rod, for there hangs no pump-rod from the iron key of these claws, for it can be of no use in the last pump. In turn, when the first pump-rod descends, each set of "claws" is lowered, each pump-rod and each piston-rod. And by this system, at the same time the water is lifted into the tanks and drained out of them; from the sump at the bottom of the shaft it is drained out, and it is poured into the trough of the tunnel. Further, around the main axle there may be placed two water wheels, if the river supplies enough water to turn them, and from the back part of each round iron crank, one or two pump-rods can be hung, each of which can move the piston-rods of three pumps. Lastly, it is necessary that the shafts from which the water is pumped out in pipes should be vertical, for as in the case of the hauling machines, all pumps which have pipes do not draw the water so high if the pipes are inclined in inclined shafts, as if they are placed vertically in vertical shafts.

[Ill.u.s.tration 187 (Suction Pumps): A--Water wheel of upper machine.

B--Its pump. C--Its trough. D--Wheel of lower machine. E--Its pump.

F--Race.]

If the river does not supply enough water-power to turn the last-described pump, which happens because of the nature of the locality or occurs during the summer season when there are daily droughts, a machine is built with a wheel so low and light that the water of ever so little a stream can turn it. This water, falling into a race, runs therefrom on to a second high and heavy wheel of a lower machine, whose pump lifts the water out of a deep shaft. Since, however, the water of so small a stream cannot alone revolve the lower water-wheel, the axle of the latter is turned at the start with a crank worked by two men, but as soon as it has poured out into a pool the water which has been drawn up by the pumps, the upper wheel draws up this water by its own pump, and pours it into the race, from which it flows on to the lower water-wheel and strikes its buckets. So both this water from the mine, as well as the water of the stream, being turned down the races on to that subterranean wheel of the lower machine, turns it, and water is pumped out of the deeper part of the shaft by means of two or three pumps.[16]

[Ill.u.s.tration 189 (Duplex suction Pumps): A--Upper axle. B--Wheel whose buckets the force of the stream strikes. C--Toothed drum. D--Second axle. E--Drum composed of rundles. F--Curved round irons. G--Rows of pumps.]

If the stream supplies enough water straightway to turn a higher and heavier water-wheel, then a toothed drum is fixed to the other end of the axle, and this turns the drum made of rundles on another axle set below it. To each end of this lower axle there is fitted a crank of round iron curved like the horns of the moon, of the kind employed in machines of this description. This machine, since it has rows of pumps on each side, draws great quant.i.ties of water.

[Ill.u.s.tration 191 (Rag and Chain Pumps): A--Wheel. B--Axle. C--Journals.

D--Pillows. E--Drum. F--Clamps. G--Drawing-chain. H--Timbers. I--b.a.l.l.s.

K--Pipe. L--Race of stream.]

Of the rag and chain pumps there are six kinds known to us, of which the first is made as follows: A cave is dug under the surface of earth or in a tunnel, and timbered on all sides by stout posts and planks, to prevent either the men from being crushed or the machine from being broken by its collapse. In this cave, thus timbered, is placed a water-wheel fitted to an angular axle. The iron journals of the axle revolve in iron pillows, which are held in timbers of sufficient strength. The wheel is generally twenty-four feet high, occasionally thirty, and in no way different from those which are made for grinding corn, except that it is a little narrower. The axle has on one side a drum with a groove in the middle of its circ.u.mference, to which are fixed many four-curved iron clamps. In these clamps catch the links of the chain, which is drawn through the pipes out of the sump, and which again falls, through a timbered opening, right down to the bottom into the sump to a balancing drum. There is an iron band around the small axle of the balancing drum, each journal of which revolves in an iron bearing fixed to a timber. The chain turning about this drum brings up the water by the b.a.l.l.s through the pipes. Each length of pipe is encircled and protected by five iron bands, a palm wide and a digit thick, placed at equal distances from each other; the first band on the pipe is shared in common with the preceding length of pipe into which it is fitted, the last band with the succeeding length of pipe which is fitted into it. Each length of pipe, except the first, is bevelled on the outer circ.u.mference of the upper end to a distance of seven digits and for a depth of three digits, in order that it may be inserted into the length of pipe which goes before it; each, except the last, is reamed out on the inside of the lower end to a like distance, but to the depth of a palm, that it may be able to take the end of the pipe which follows. And each length of pipe is fixed with iron clamps to the timbers of the shaft, that it may remain stationary. Through this continuous series of pipes, the water is drawn by the b.a.l.l.s of the chain up out of the sump as far as the tunnel, where it flows but into the drains through an aperture in the highest pipe. The b.a.l.l.s which lift the water are connected by the iron links of the chain, and are six feet distant from one another; they are made of the hair of a horse's tail sewn into a covering to prevent it from being pulled out by the iron clamps on the drum; the b.a.l.l.s are of such size that one can be held in each hand. If this machine is set up on the surface of the earth, the stream which turns the water-wheel is led away through open-air ditches; if in a tunnel, the water is led away through the subterranean drains.

The buckets of the water-wheel, when struck by the impact of the stream, move forward and turn the wheel, together with the drum, whereby the chain is wound up and the b.a.l.l.s expel the water through the pipes. If the wheel of this machine is twenty-four feet in diameter, it draws water from a shaft two hundred and ten feet deep; if thirty feet in diameter, it will draw water from a shaft two hundred and forty feet deep. But such work requires a stream with greater water-power.

The next pump has two drums, two rows of pipes and two drawing-chains whose b.a.l.l.s lift out the water; otherwise they are like the last pump.

This pump is usually built when an excessive amount of water flows into the sump. These two pumps are turned by water-power; indeed, water draws water.

The following is the way of indicating the increase or decrease of the water in an underground sump, whether it is pumped by this rag and chain pump or by the first pump, or the third, or some other. From a beam which is as high above the shaft as the sump is deep, is hung a cord, to one end of which there is fastened a stone, the other end being attached to a plank. The plank is lowered down by an iron wire fastened to the other end; when the stone is at the mouth of the shaft the plank is right down the shaft in the sump, in which water it floats. This plank is so heavy that it can drag down the wire and its iron clasp and hook, together with the cord, and thus pull the stone upwards. Thus, as the water decreases, the plank descends and the stone is raised; on the contrary, when the water increases the plank rises and the stone is lowered. When the stone nearly touches the beam, since this indicates that the water has been exhausted from the sump by the pump, the overseer in charge of the machine closes the water-race and stops the water-wheel; when the stone nearly touches the ground at the side of the shaft, this indicates that the sump is full of water which has again collected in it, because the water raises the plank and thus the stone drags back both the rope and the iron wire; then the overseer opens the water-race, whereupon the water of the stream again strikes the buckets of the water-wheel and turns the pump. As workmen generally cease from their labours on the yearly holidays, and sometimes on working days, and are thus not always near the pump, and as the pump, if necessary, must continue to draw water all the time, a bell rings aloud continuously, indicating that this pump, or any other kind, is uninjured and nothing is preventing its turning. The bell is hung by a cord from a small wooden axle held in the timbers which stand over the shaft, and a second long cord whose upper end is fastened to the small axle is lowered into the shaft; to the lower end of this cord is fastened a piece of wood; and as often as a cam on the main axle strikes it, so often does the bell ring and give forth a sound.

[Ill.u.s.tration 193 (Rag and Chain Pumps): A--Upright axle. B--Toothed wheel. C--Teeth. D--Horizontal axle. E--Drum which is made of rundles.

F--Second drum. G--Drawing-chain. H--The b.a.l.l.s.]

The third pump of this kind is employed by miners when no river capable of turning a water-wheel can be diverted, and it is made as follows.

They first dig a chamber and erect strong timbers and planks to prevent the sides from falling in, which would overwhelm the pump and kill the men. The roof of the chamber is protected with contiguous timbers, so arranged that the horses which pull the machine can travel over it. Next they again set up sixteen beams forty feet long and one foot wide and thick, joined by clamps at the top and spreading apart at the bottom, and they fit the lower end of each beam into a separate sill laid flat on the ground, and join these by a post; thus there is created a circular area of which the diameter is fifty feet. Through an opening in the centre of this area there descends an upright square axle, forty-five feet long and a foot and a half wide and thick; its lower pivot revolves in a socket in a block laid flat on the ground in the chamber, and the upper pivot revolves in a bearing in a beam which is mortised into two beams at the summit beneath the clamps; the lower pivot is seventeen feet distant from either side of the chamber, _i.e._, from its front and rear. At the height of a foot above its lower end, the axle has a toothed wheel, the diameter of which is twenty-two feet.

This wheel is composed of four spokes and eight rim pieces; the spokes are fifteen feet long and three-quarters of a foot wide and thick[17]; one end of them is mortised in the axle, the other in the two rims where they are joined together. These rims are three-quarters of a foot thick and one foot wide, and from them there rise and project upright teeth three-quarters of a foot high, half a foot wide, and six digits thick.

These teeth turn a second horizontal axle by means of a drum composed of twelve rundles, each three feet long and six digits wide and thick. This drum, being turned, causes the axle to revolve, and around this axle there is a drum having iron clamps with fourfold curves in which catch the links of a chain, which draws water through pipes by means of b.a.l.l.s.

The iron journals of this horizontal axle revolve on pillows which are set in the centre of timbers. Above the roof of the chamber there are mortised into the upright axle the ends of two beams which rise obliquely; the upper ends of these beams support double cross-beams, likewise mortised to the axle. In the outer end of each cross-beam there is mortised a small wooden piece which appears to hang down; in this wooden piece there is similarly mortised at the lower end a short board; this has an iron key which engages a chain, and this chain again a pole-bar. This machine, which draws water from a shaft two hundred and forty feet deep, is worked by thirty-two horses; eight of them work for four hours, and then these rest for twelve hours, and the same number take their place. This kind of machine is employed at the foot of the Harz[18] mountains and in the neighbourhood. Further, if necessity arises, several pumps of this kind are often built for the purpose of mining one vein, but arranged differently in different localities varying according to the depth. At Schemnitz, in the Carpathian mountains, there are three pumps, of which the lowest lifts water from the lowest sump to the first drains, through which it flows into the second sump; the intermediate one lifts from the second sump to the second drain, from which it flows into the third sump; and the upper one lifts it to the drains of the tunnel, through which it flows away. This system of three machines of this kind is turned by ninety-six horses; these horses go down to the machines by an inclined shaft, which slopes and twists like a screw and gradually descends. The lowest of these machines is set in a deep place, which is distant from the surface of the ground 660 feet.

[Ill.u.s.tration 194 (Rag and Chain Pumps): A--Axle. B--Drum.

C--Drawing-chain. D--b.a.l.l.s. E--Clamps.]

The fourth species of pump belongs to the same genera, and is made as follows. Two timbers are erected, and in openings in them, the ends of a barrel revolve. Two or four strong men turn the barrel, that is to say, one or two pull the cranks, and one or two push them, and in this way help the others; alternately another two or four men take their place.

The barrel of this machine, just like the horizontal axle of the other machines, has a drum whose iron clamps catch the links of a drawing-chain. Thus water is drawn through the pipes by the b.a.l.l.s from a depth of forty-eight feet. Human strength cannot draw water higher than this, because such very heavy labour exhausts not only men, but even horses; only water-power can drive continuously a drum of this kind.

Several pumps of this kind, as of the last, are often built for the purpose of mining on a single vein, but they are arranged differently for different positions and depths.

[Ill.u.s.tration 195 (Rag and Chain Pumps): A--Axles. B--Levers. C--Toothed drum. D--Drum made of rundles. E--Drum in which iron clamps are fixed.]

The fifth pump of this kind is partly like the third and partly like the fourth, because it is turned by strong men like the last, and like the third it has two axles and three drums, though each axle is horizontal. The journals of each axle are so fitted in the pillows of the beams that they cannot fly out; the lower axle has a crank at one end and a toothed drum at the other end; the upper axle has at one end a drum made of rundles, and at the other end, a drum to which are fixed iron clamps, in which the links of a chain catch in the same way as before, and from the same depth, draw water through pipes by means of b.a.l.l.s. This revolving machine is turned by two pairs of men alternately, for one pair stands working while the other sits taking a rest; while they are engaged upon the task of turning, one pulls the crank and the other pushes, and the drums help to make the pump turn more easily.

[Ill.u.s.tration 197 (Rag and Chain Pumps): A--Axles. B--Wheel which is turned by treading. C--Toothed wheel. D--Drum made of rundles. E--Drum to which are fixed iron clamps. F--Second wheel. G--b.a.l.l.s.]

The sixth pump of this kind likewise has two axles. At one end of the lower axle is a wheel which is turned by two men treading, this is twenty-three feet high and four feet wide, so that one man may stand alongside the other. At the other end of this axle is a toothed wheel.

The upper[19] axle has two drums and one wheel; the first drum is made of rundles, and to the other there are fixed the iron clamps. The wheel is like the one on the second machine which is chiefly used for drawing earth and broken rock out of shafts. The treaders, to prevent themselves from falling, grasp in their hands poles which are fixed to the inner sides of the wheel. When they turn this wheel, the toothed drum being made to revolve, sets in motion the other drum which is made of rundles, by which means again the links of the chain catch to the cleats of the third drum and draw water through pipes by means of b.a.l.l.s,--from a depth of sixty-six feet.

[Ill.u.s.tration 199 (Baling Water): A--Reservoir. B--Race. C, D--Levers.

E, F--Troughs under the water gates. G, H--Double rows of buckets.

I--Axle. K--Larger drum. L--Drawing-chain. M--Bag. N--Hanging cage.

O--Man who directs the machine. P, Q--Men emptying bags.]

But the largest machine of all those which draw water is the one which follows. First of all a reservoir is made in a timbered chamber; this reservoir is eighteen feet long and twelve feet wide and high. Into this reservoir a stream is diverted through a water-race or through the tunnel; it has two entrances and the same number of gates. Levers are fixed to the upper part of these gates, by which they can be raised and let down again, so that by one way the gates are opened and in the other way closed. Beneath the openings are two plank troughs which carry the water flowing from the reservoir, and pour it on to the buckets of the water-wheel, the impact of which turns the wheel. The shorter trough carries the water, which strikes the buckets that turn the wheel toward the reservoir, and the longer trough carries the water which strikes those buckets that turn the wheel in the opposite direction. The casing or covering of the wheel is made of joined boards to which strips are affixed on the inner side. The wheel itself is thirty-six feet in diameter, and is mortised to an axle, and it has, as I have already said, two rows of buckets, of which one is set the opposite way to the other, so that the wheel may be turned toward the reservoir or in the opposite direction. The axle is square and is thirty-five feet long and two feet thick and wide. Beyond the wheel, at a distance of six feet, the axle has four hubs, one foot wide and thick, each one of which is four feet distant from the next; to these hubs are fixed by iron nails as many pieces of wood as are necessary to cover the hubs, and, in order that the wood pieces may fit tight, they are broader on the outside and narrower on the inside; in this way a drum is made, around which is wound a chain to whose ends are hooked leather bags. The reason why a drum of this kind is made, is that the axle may be kept in good condition, because this drum when it becomes worn away by use can be repaired easily. Further along the axle, not far from the end, is another drum one foot broad, projecting two feet on all sides around the axle. And to this, when occasion demands, a brake is applied forcibly and holds back the machine; this kind of brake I have explained before.

Near the axle, in place of a hopper, there is a floor with a considerable slope, having in front of the shaft a width of fifteen feet and the same at the back; at each side of it there is a stout post carrying an iron chain which has a large hook. Five men operate this machine; one lets down the doors which close the reservoir gates, or by drawing down the levers, opens the water-races; this man, who is the director of this machine, stands in a hanging cage beside the reservoir.

When one bag has been drawn out nearly as far as the sloping floor, he closes the water gate in order that the wheel may be stopped; when the bag has been emptied he opens the other water gate, in order that the other set of buckets may receive the water and drive the wheel in the opposite direction. If he cannot close the water-gate quickly enough, and the water continues to flow, he calls out to his comrade and bids him raise the brake upon the drum and stop the wheel. Two men alternately empty the bags, one standing on that part of the floor which is in front of the shaft, and the other on that part which is at the back. When the bag has been nearly drawn up--of which fact a certain link of the chain gives warning--the man who stands on the one part of the floor, catches a large iron hook in one link of the chain, and pulls out all the subsequent part of the chain toward the floor, where the bag is emptied by the other man. The object of this hook is to prevent the chain, by its own weight, from pulling down the other empty bag, and thus pulling the whole chain from its axle and dropping it down the shaft. His comrade in the work, seeing that the bag filled with water has been nearly drawn out, calls to the director of the machine and bids him close the water of the tower so that there will be time to empty the bag; this being emptied, the director of the machine first of all slightly opens the other water-gate of the tower to allow the end of the chain, together with the empty bag, to be started into the shaft again, and then opens entirely the water-gates. When that part of the chain which has been pulled on to the floor has been wound up again, and has been let down over the shaft from the drum, he takes out the large hook which was fastened into a link of the chain. The fifth man stands in a sort of cross-cut beside the sump, that he may not be hurt, if it should happen that a link is broken and part of the chain or anything else should fall down; he guides the bag with a wooden shovel, and fills it with water if it fails to take in the water spontaneously. In these days, they sew an iron band into the top of each bag that it may constantly remain open, and when lowered into the sump may fill itself with water, and there is no need for a man to act as governor of the bags. Further, in these days, of those men who stand on the floor the one empties the bags, and the other closes the gates of the reservoir and opens them again, and the same man usually fixes the large hook in the link of the chain. In this way, three men only are employed in working this machine; or even--since sometimes the one who empties the bag presses the brake which is raised against the other drum and thus stops the wheel--two men take upon themselves the whole labour.

But enough of haulage machines; I will now speak of ventilating machines. If a shaft is very deep and no tunnel reaches to it, or no drift from another shaft connects with it, or when a tunnel is of great length and no shaft reaches to it, then the air does not replenish itself. In such a case it weighs heavily on the miners, causing them to breathe with difficulty, and sometimes they are even suffocated, and burning lamps are also extinguished. There is, therefore, a necessity for machines which the Greeks call [Greek: pneumatikai] and the Latins _spiritales_--though they do not give forth any sound--which enable the miners to breathe easily and carry on their work.

[Ill.u.s.tration 201 (Windsails for Ventilation): A--Sills. B--Pointed stakes. C--Cross-beams. D--Upright planks. E--Hollows. F--Winds.

G--Covering disc. H--Shafts. I--Machine without a covering.]

These devices are of three genera. The first receives and diverts into the shaft the blowing of the wind, and this genus is divided into three species, of which the first is as follows. Over the shaft--to which no tunnel connects--are placed three sills a little longer than the shaft, the first over the front, the second over the middle, and the third over the back of the shaft. Their ends have openings, through which pegs, sharpened at the bottom, are driven deeply into the ground so as to hold them immovable, in the same way that the sills of the windla.s.s are fixed. Each of these sills is mortised into each of three cross-beams, of which one is at the right side of the shaft, the second at the left, and the third in the middle. To the second sill and the second cross-beam--each of which is placed over the middle of the shaft--planks are fixed which are joined in such a manner that the one which precedes always fits into the groove of the one which follows. In this way four angles and the same number of intervening hollows are created, which collect the winds that blow from all directions. The planks are roofed above with a cover made in a circular shape, and are open below, in order that the wind may not be diverted upward and escape, but may be carried downward; and thereby the winds of necessity blow into the shafts through these four openings. However, there is no need to roof this kind of machine in those localities in which it can be so placed that the wind can blow down through its topmost part.

[Ill.u.s.tration 202 (Windsails for Ventilation): A--Projecting mouth of conduit. B--Planks fixed to the mouth of the conduit which does not project.]

The second machine of this genus turns the blowing wind into a shaft through a long box-shaped conduit, which is made of as many lengths of planks, joined together, as the depth of the shaft requires; the joints are smeared with fat, glutinous clay moistened with water. The mouth of this conduit either projects out of the shaft to a height of three or four feet, or it does not project; if it projects, it is shaped like a rectangular funnel, broader and wider at the top than the conduit itself, that it may the more easily gather the wind; if it does not project, it is not broader than the conduit, but planks are fixed to it away from the direction in which the wind is blowing, which catch the wind and force it into the conduit.

[Ill.u.s.tration 203 (Windsails for Ventilation): A--Wooden barrels.

B--Hoops. C--Blow-holes. D--Pipe. E--Table. F--Axle. G--Opening in the bottom of the barrel. H--Wing.]