Subterranean mining

requires two very distinct cla es of workings; the preparatory , and those for extraction . The preparatory consist in galleries, or in pits and galleries destined to conduct the miner to the point most proper for attacking the deposit of ore, for tracing it all round this point, for preparing chambers of excavation, and for concerting measures with a view to the circulation of air, the discharge of waters, and the transport of the extracted minerals. If the vein or bed in question be placed in a mountain, and if its direction forms a very obtuse angle with the line of the slope, the miner begins by opening in its side, at the lowest po ible level, a gallery of elongation, which serves at once to give i ue to the waters, to explore the deposit through a considerable extent, and then to follow it in another direction; but to commence the real mining operations, he pierces either shafts or galleries, according to the slope of the deposit, acro the first gallery. For a stratum little inclined to the horizon, placed beneath a plain, the first thing is to pierce two vertical shafts, which are usually made to arrive at two points in the same line of slope, and a gallery is driven to unite them. It is, in the first place, for the sake of circulation of air that these two pits are sunk; one of them, which is also destined for the drainage of the waters, should reach the lowest point of the intended workings. If a vein is intersected by transverse ones, the shafts are placed so as to follow, or, at least, to cut through the intersections. When the mineral ores lie in nearly vertical ma es, it is right to avoid, as far as po ible, sinking pits into their interior. These should rather be perforated at one side of their floor, even at some considerable distance, to avoid all risk of crumbling the ores into a heap of rubbish, and overwhelming the workmen. With a vein of le than two yards thick, as soon as the preparatory labours have brought the miners to the point of the vein from which the ulterior workings are to ramify, whenever a circulation of air has been secured, and an outlet to the water and the matters mined, the first object is to divide the ma of ore into large parallelopipeds, by means of oblong galleries, pierced 20 or 25 yards below one another, with pits of communication opened up, 30, 40, or 50 yards asunder, which follow the slope of the vein. These galleries and shafts are usually of the same breadth as the vein, unle when it is very narrow, in which case it is requisite to cut out a portion of the roof or the floor. Such workings serve at once the purposes of mining, by affording a portion of ore, and the complete investigation of the nature and riches of the vein, a certain extent of which is thus prepared before removing the cubical ma es. It is proper to advance first of all, in this manner, to the greatest distance from the central point which can be mined with economy, and afterwards to remove the parallelopiped blocks, in working back to that point. This latter operation may be carried on in two different ways; of which one consists in attacking the ore from above; and another from below. In either case, the excavations are disposed in steps similar to a stair upon their upper or under side. The first is styled a working in direct or descending steps; and the second a working in reverse , or ascending steps. IMG:4147767755307473660_illo0841.png:Section of mine 1. Suppose, for example, that the post N , fig. 714. , included between the horizontal gallery A C , and the shaft A B , is to be excavated by direct steps, a workman stationed upon a scaffold at the point a , which forms the angle between the shaft and the elongated drift, attacks the rock in front of him and beneath his feet. Whenever he has cut out a parallelopiped (a rectangular ma ), of from four to six yards broad, and two yards high, a second miner is set to work upon a scaffold at a′ , two yards beneath the first, who, in like manner, excavates the rock under his feet and before him. As soon as the second miner has removed a post of four or six yards in width, by two in height, a third begins upon a scaffold at a′ ′ to work out a third step. Thus, as many workmen are employed as there are steps to be made between the two oblong horizontal galleries which extend above and below the ma to be excavated; and since they all proceed simultaneously, they continue working in similar positions, in floors, over each other, as upon a stair with very long wide steps. As they advance, the miners construct before them wooden floors c c c c , for the purpose of supporting the rubbish which each workman extracts from his own step. This floor, which should be very solid, serves also for wheeling out his barrow filled with ore. The round billets which support the planks sustain the roof or the wall of the mineral vein or bed under operation. If the rubbish be very considerable, as is commonly the case, the floor planks are lost. However strongly they may be made, as they cannot be repaired, they sooner or later give way under the enormous pre ure of the rubbish; and as all the weight is borne by the roof of the oblong gallery underneath, this must be sufficiently timbered. By this ingenious plan, a great many miners may go to work together upon a vein without mutual interference; as the portions which they detach have always two faces at least free, they are consequently more easily separable, either with gunpowder or with the pick. Should the vein be more than a yard thick, or if its substance be very refractory, two miners are set upon each step. b b b b indicate the quadrangular ma es that are cut out succe ively downwards; and 1 1, 2 2, 3 3, forwards; the lines of small circles are the sections of the ends of the billets which support the floors. IMG:4147767755307473660_illo0842.png:Section of mine 2. To attack a ma Y , fig. 715. , a scaffold m , is erected in one of its terminal pits P P , at the level of the ceiling of the gallery R R ′, where it terminates below. A miner placed on this scaffold, cuts off at the angle of this ma a parallelopiped 1, from one to two yards high, by six or eight long. When he has advanced thus far, there is placed in the same pit, upon another scaffold m′ , a second miner, who attacks the vein above the roof of the first cutting, and hews down, above the parallelopiped 1, a parallelopiped of the same dimensions 1′ , while the first is taking out another 2, in advance of 1. When the second miner has gone forward 6 or 8 yards, a third is placed also in the same pit. He commences the third step, while the first two miners are pushing forwards theirs, and so in succe ion. In this mode of working, as well as in the preceding, it is requisite to support the rubbish and the walls of the vein. For the first object, a single floor n n n , may be sufficient, constructed above the lower gallery, substantial enough to bear all the rubbish, as well as the miners. In certain cases, an arched roof may be substituted; and in others, several floors are laid at different heights. The sides of the vein are supported by means of pieces of wood fixed between them perpendicularly to their planes. Sometimes, in the middle of the rubbish, small pits are left at regular distances apart, through which the workmen throw the ore coarsely picked, down into the lower gallery. The rubbish occasionally forms a slope f f f , so high that miners placed upon it can work conveniently. When the rich portions are so abundant as to leave too little rubbish to make such a sloping platform, the miners plant themselves upon movable floors, which they carry forward along with the excavations. These two modes of working in the step-form , have peculiar advantages and disadvantages; and each is preferred to the other according to circumstances. In the descending workings or in direct steps , fig. 714. , the miner is placed on the very ma or substance of the vein; he works commodiously before him; he is not exposed to the splinters which may fly off from the roof; but by this plan he is obliged to employ a great deal of timber to sustain the rubbish; and the wood is fixed for ever. In the ascending workings , or in reversed steps , fig. 715. , the miner is compelled to work in the re-entering angle formed between the roof and the front wall of his excavation, a posture sometimes oppre ive; but the weight of the ore conspires with his efforts to make it fall. He employs le timber than in the workings with direct steps . The sorting of the ore is more difficult than in the descending working , because the rich ore is sometimes confounded with the heap of rubbish on which it falls. When seams of diluvium or gravel-mud, occur on one of the sides of the vein, or on both, they render the quarrying of the ore more easy, by affording the means of uncovering the ma to be cut down, upon an additional face. Should the vein be very narrow, it is nece ary to remove a portion of the sterile rock which encloses it, in order to give the work a sufficient width to enable the miner to advance. If, in this case, the vein be quite distinct from the rock, the labour may be facilitated, as well as the separation of the ore, by disengaging the vein, on one of its faces through a certain extent, the rock being attacked separately. This operation is called stripping the vein . When it is thus uncovered, a shot of gunpowder is sufficient to detach a great ma of it, unmixed with sterile stones. By the methods now described, only those parallelopipeds are cut out, either in whole or in part, which present indications of richne adequate to yield a prospect of benefit. In other cases, it is enough to follow out the threads of ore which occur, by workings made in their direction. The miner, in searching within the crust of the earth for the riches which it conceals, is exposed to many dangers. The rocks amidst which he digs are seldom or never entire, but are almost always traversed by clefts in various directions, so that impending fragments threaten to fall and crush him at every instant. He is even obliged at times to cut through rotten friable rocks or alluvial loams. Fresh atmospheric air follows him with difficulty in the narrow channels which he lays open before him; and the waters which circulate in the subterranean seams and fi ures filter ince antly into his excavation, and tend to fill it. Let us now take a view of the means he employs to escape from these three cla es of dangers. 1. Of the timbering of excavations. —The excavations of mines, are divisible into three principal species; shafts , galleries , and chambers . When the width of these excavations is inconsiderable, as is commonly the case with shafts and galleries, their sides can sometimes stand upright of themselves; but more frequently they require to be propped or stayed by billets of wood, or by walls built with bricks or stones; or even by stuffing the space with rubbish. These three kinds of support are called timbering , walling , and filling up . Timbering is most used. It varies in form for the three species of excavations, according to the solidity of the walls which it is destined to sustain. IMG:4147767755307473660_illo0843.png:Supported gallery In a gallery, for example, it may be sufficient to support merely the roof, by means of joists placed acro , bearing at their two ends in the rock; or the roof and the two walls by means of an upper joist S , fig. 716. , which is then called a cap or cornice beam , resting on two lateral upright posts or stanchions , a , b , to which a slight inclination towards each other is given, so that they approach a little at the top, and rest entirely upon the floor. At times, only one of the walls and the roof need support. This case is of frequent occurrence in pipe veins. Pillars are then set up only on one side, and on the other the joists rest in holes of the rock. It may happen that the floor of the gallery shall not be sufficiently firm to afford a sure foundation to the standards; and it may be nece ary to make them rest on a horizontal piece called the sole . This is timbering with complete frames . The upright posts are usually set directly on the sole; but the extremities of the cap or ceiling, and the upper ends of the standards , are mortised in such a manner that these cannot come nearer, whereby the cap shall po e its whole force of resistance. In friable and shivery rocks there is put behind these beams, both upon the ceiling and the sides, facing boards , which are planks placed horizontally, or spars of cleft wood, set so close together as to leave no interval. They are called fascines in French. In ordinary ground, the miner puts up these planks in proportion as he goes forwards; but in a loose soil, such as sand or gravel, he must mount them a little in advance. He then drives into the ma behind the wooden frame-work, thick but sharp-pointed planks or stakes, and which, in fact, form the sides of the cavity, which he proceeds to excavate. Their one extremity is thus supported by the earth in which it is thrust, and their other end by the last framing. Whenever the miner gets sufficiently on, he sustains the walls by a new frame. The size of the timber, as well as the distance between the frames or stanchions , depends on the degree of pre ure to be resisted. When a gallery is to serve at once for several distinct purposes, a greater height is given to it; and a flooring is laid on it at a certain level. If, for example, a gallery is to be employed, both for the transport of the ores and the discharge of the waters, a floor e e , fig. 715. , is constructed above the bottom, over which the carriages are wheeled, and under which the waters are discharged. The timbering of shafts varies in form, as well as that of galleries, according to the nature and the locality of the ground which they traverse, and the purposes which they are meant to serve. The shafts intended to be stayed with timber are usually square or rectangular, because this form, in itself more convenient for the miner, renders the execution of the timbering more easy. The wood-work consists generally of rectangular frames, the spars of which are about eight inches in diameter, and placed at a distance asunder of from a yard to a yard and a half. The spars are never placed in contact, except when the pre ure of the earth and the waters is very great. The pieces composing the frames are commonly united by a half-check, and the longer of the two pieces extends often beyond the angles, to be rested in the rock. Whether the shaft is vertical or inclined, the frame-work is always placed so that its plane may be perpendicular to the axis of the pit. It happens sometimes in inclined shafts that there are only two sides, or even a single one, which needs to be propped. These are stayed by means of cro beams, which rest at their two ends in the rock. When the frames do not touch one another, strong planks or stakes are fastened behind them to sustain the ground. To these planks the frames are firmly connected, so that they cannot slide. In this case the whole timbering will be supported, when the lower frame is solidly fixed, or when the pieces from above pa by its angles to be abutted upon the ground. In the large rectangular shafts, which serve at once for extracting the ores, for the discharge of the waters, and the descent of the workmen, the spaces destined for these several purposes are in general separated by partitions, which also serve to increase the strength of the timberings, by acting as buttre es to the planks in the long sides of the frame-work. Occasionally a partition separates the ascending from the descending basket, to prevent their jostling.—Lastly, particular pa ages are left for ventilation. As it is desirable that the wood shall retain its whole force, only those pieces are squared which absolutely require it. The spars of the frames in shafts and galleries are deprived merely of their bark, which by holding moisture, would accelerate the decomposition of the wood. The alburnum of oak is also removed. Resinous woods, like the pine, last much shorter than the oak, the beech, and the cherry-tree; though the larch is used with advantage. The oak has been known to last upwards of 40 years; while the resinous woods decay frequently in 10. The fresher the air in mines, the more durable is the timbering. IMG:4147767755307473660_illo0844a.png:Section of mine shaft IMG:4147767755307473660_illo0844b.png:Section of mine shaft The marginal figs. 717 , 718. represent two vertical sections of a shaft, the one at right angles to the other, with the view of showing the mode of sustaining the walls of the excavation by timbering. It is copied from an actual mine in the Hartz. There we may observe the spaces allotted to the descent of the miners by ladders, to the drainage of the waters by pumps P , and rods t , and to the extraction of the mineral substances by the baskets B . a , b , c , f , h , k , various cro timbers; A , C , E , upright do.; R , pump cistern; V , W , corve-ways. The shafts here shown, are excavated in the line of the vein itself,—the rock enclosing it being seen in the second figure . In a great many mines it is found advantageous to support the excavations by brick or stone buildings, constructed either with or without mortar. These constructions are often more costly than wooden ones, but they last much longer, and need fewer repairs. They are employed instead of timberings, to support the walls and roof of galleries, to line the sides of shafts, and to bear up the roofs of excavations. Sometimes the two sides of a gallery are lined with vertical walls, and its roof is supported by an ogee vault, or an arch. If the sides of the mine are solid, a simple arch is sufficient to sustain the roof and at other times the whole surface of a gallery is formed of a single elliptic vault, the great axis of which is vertical; and the bottom is surmounted by a wooden plank, under which the waters run off; see fig. 719. Walled shafts also are sometimes constructed in a circular or elliptic form, which is better adapted to resist the pre ure of the earth and waters. Rectangular shafts of all dimensions, however, are frequently walled. The sides of an excavation may also be supported by filling it completely with rubbish. Wherever the sides need to be supported for some time without the nece ity of pa ing along them, it is often more economical to stuff them up with rubbish, than to keep up their supports. In the territory of Liege, for example, there have been shafts thus filled up for several centuries; and which are found to be quite entire when they are emptied. The rubbish is also useful for forming roads among steep strata, for closing air-holes, and forming canals of ventilation. IMG:4147767755307473660_illo0845a.png:Mining masonry IMG:4147767755307473660_illo0845b.png:Mining masonry Figs. 719. 720. 721. represent the principal kinds of mason-work employed in the galleries and shafts of mines. Fig. 722. exhibits the walling in of the cage of an overshot water-wheel, as mounted within a mine. Before beginning to build, an excavation large enough must be made in the gallery to leave a space three feet and a half high for the workmen to stand in, after the brick-work is completed. Between the two opposite sides, cro beams of wood must be fixed at certain distances, as chords of the vault, over which the rock must be hollowed out to receive the arch-stones, and the centring must then be placed, covered with deals to receive the vou oirs , beginning at the flanks and ending with the key-stone. When the vault is finished through a certain extent, the interval between the arch and the rock must be rammed full of rubbish, leaving pa ages if nece ary through it and the arch, for currents of water. In walling galleries, attention must be paid to the direction of the pre ure, and to build vertically or with a slope accordingly. Should the pre ure be equal in all directions, a closed vault, like fig. 719. , should be formed. For walls not far from the vertical, salient or buttre ed arches are employed, as shown in fig. 720. , called in German überspringende bogen ; for other cases, twin-arches are preferred, with an upright wall between. Fig. 721. is a transverse section of a walled drain-gallery, from the grand gallery of the Hartz; see also fig. 722. a is the rock which needs to be supported only at the sides and top; b , the mason work, a curve formed of the three circular arcs upon one level; c , the floor for the watercourse. Fig. 719. is a cro section of a walled gallery, as at Schneeberg, Rothenburg, Idria, .; d , is the rock, which is not solid either at the flanks, roof, or floor; e , the elliptic mason work; f , the wooden floor for the waggons, which is sometimes, however, arched in brick to allow of a watercourse beneath it. Fig. 720. shows two vertical projections of a portion of a walled shaft with buttre es, as built at the mine Vater Abraham , near Marienberg. J is a section in the direction of the vein g h , to show the roof of the shaft. I , a section exhibiting the slope of the vein g h , into which the shaft is sunk; m is the wall of the vein; k is the roof of the same vein; n , buttre es resting upon the flanks of the shaft; g , great arcs on which the buttre es bear; y , vertical mason work; z , a wall which divides the shaft into two compartments, of which the larger p is that for extracting the ore, and the smaller for the draining and descent of the miners. Fig. 722. C D is the shaft in which the vertical crank-rods c g , e d , move up and down. F , is a double hydraulic wheel, which can be stopped at pleasure by a brake mounted upon the machine of extraction. G , is the drum of the gig or whim for raising the corves or tubs ( tonnes ); H , is the level of the ground, with the carpentry which supports the whim and its roof. k , is the key-stone of the ogee arch which covers the water-wheel; a , is the opening or window, traversed by the extremity of the driving shaft, upon each side of the water-wheel, through which a workman may enter to adjust or repair it; c b , line of conduits for the streams of water which fall upon the hydraulic wheel; c , g , double crank with rods, whose motion is taken off the left side of the wheel; e , d , the same upon the right side. The distance from H to F is about 22 yards. Figs. 723. 724. present two vertical sections of the shaft of a mine walled, like the roof of a cavern, communicating with the galleries of the roof and the wall of the vein, and well arranged for both the extraction of the ore, and the descent of the miners. The vertical partition of the shaft for separating the pa age for the corves or tubs from the ladders is omitted in the figure, for the sake of clearne . IMG:4147767755307473660_illo0846a.jpg:Section of mine shaft Fig. 723 and 724 enlarged (264 kB) In fig. 723. , A , B are the side walls supported upon the buttre es C and D ; in fig. 724. , E is the masonry of the wall, borne upon the arch F at the entrance to a gallery; the continuation being at G , which is sustained by a similar arch built lower. L , is the vault arch of the roof, supported upon another vault M , which presents a double curvature, at the entrance of a gallery; at H is the continuation of the arch or vault L , which underneath is supported in like manner at the entrance of a lower gallery. a b , c d , fig. 723. , are small upright guide-bars or rods for one of the corves, or kibbles. e f , g h , are similar guide-bars for the other corf. i i , are cro -bars of wood, which support the stays of the ladders of descent. k k , are also cro -bars by which the guide-rods are secured. t , a corf , or extraction kibble, furnished with friction rollers; the other corf is supposed to be drawn up to a higher level, in the other vertical pa age. IMG:4147767755307473660_illo0846b.png:Timbered galleries Figs. 725. 726. represent in a vertical section the mode of timbering the galleries of the silver and lead mines at Andreas berg in the Hartz. Fig. 725. shows the plan viewed from above. Upon the roof of the timbering, the workman throws the waste rubbish, and in the empty space below, which is shaded black, he transports in his waggons or wheelbarrows the ores towards the mouth of the mine. Fig. 726. is the cro section of the gallery. In the two figures, a represents the rock, and b the timbering; round which there is a garniture of small spars or lathes for the purpose of drainage and ventilation, with the view of promoting the durability of the wood-work. The working of minerals by the ma is well exemplified a few leagues to the north of Siegen, near the village of Müsen, in a mine of iron and other metals, called Stahlberg , which forms the main wealth of the country. The plan of working is termed the excavation of a direct or transverse ma . It shows in its upper part the danger of bad mining, and in its inferior portion, the regular workings, by whose means art has eventually prevented the destruction of a precious mineral deposit. IMG:4147767755307473660_illo0847a.png:Section of bed of ore Fig. 727. is a vertical section of the bed of ore, which is a direct ma of spathose iron, contained in transition rock (greywacke). a , a , a , are pillars of the sparry ore, reserved to support the succe ive stages or floors, which are numbered 1. 2. 3. .; b , b , b , are excavations worked in the ore; which exhibit at the present day several floors of arches, of greater or le magnitude, according to the localities. It may be remarked, that where the metallic deposit forms one entire ma , rich in spathose iron ore of good quality, there is generally given to the vaults a height of three fathoms; leaving a thickne over the roof of two fathoms, on account of the numerous fi ures which pervade the ma . But where this ma is divided into three principal branches, the roof of the vaults has only a fathom and a half of thickne , while the excavation is three fathoms and a half high. In the actual state of the workings, it may be estimated that from all this direct ma , there is obtained no more out of every floor than one-third of the mineral. Two-thirds remain as labours of reserve, which may be resumed at some future day, in consequence of the regularity and the continuation of the subterranean workings. e is a shaft for extraction, communicating below with the gallery of efflux k ; h is an upper gallery of drainage, which runs in different directions (one only being visible in this section) over a length of 400 fathoms. The lower gallery k runs 646 fathoms in a straight line. The mine of Stahlberg has furnished annually on an average since 1760 about 25,000 cubic feet (French) of an excellent spathose ore of iron. m m , represents the ma of sparry iron. Figs. 728 , 729 , 730. represent the cro system of mining, which consists in forming galleries through a mineral deposit, from its wall or floor towards its roof, and not, as usual, in the direction of its length. This mode was contrived towards the middle of the 18th century, for working the very thick veins of the Schemnitz mine in Hungary, and it is now employed with advantage in many places, particularly at Idria in Carniola. In the two sections figs. 728. , 730. , as well as in the ground plan fig. 729. , the wall is denoted by m m , and the roof by t t . A first gallery of prolongation E F , fig. 730. , being formed to the wall, transverse cuts, a a , are next established at right angles to this gallery, so that between every two there may be room enough to place three others, b , c , b , fig. 729. From each of the cuts a , ore is procured by advancing with the help of timbering, till the roof t be reached. When this is done, these first cuts a , are filled up with rubbish, laid upon pieces of timber with which the ground is covered, so that if eventually, it should be wished to mine underneath, no downfall of detritus is to be feared. These heaps of rubbish rise only to within a few inches of the top of the cuts a , in order that the working of the upper story may be easier, the bed of ore being there already laid open upon its lower face. IMG:4147767755307473660_illo0847b.png:Section of gallery IMG:4147767755307473660_illo0848a.png:Plan of gallery IMG:4147767755307473660_illo0848b.png:Section of gallery In proportion as the cuts a , of the first story E F , are thus filled up, the greater part of the timbering is withdrawn, and made use of elsewhere. The intermediate cuts b , c , b , are next mined in like manner, either beginning with the cuts c , or the cuts b , according to the localities. From fig. 729. it appears that the working may be so arranged, that in case of nece ity, there may be always between two cuts in activity the distance of three cuts, either not made, or filled up with rubbish. Hence, all the portion of the bed of ore may be removed, which corresponds to a first story E F fig. 730. , and this portion is replaced by rubbish. The exploration of the upper stories E ′ F ′, E 2 F 2 , E 3 F 3 , is now prepared in a similar manner; with which view shafts h h 3 , k k 3 , are formed from below upwards in the wall m of the deposit, and from these shafts oblong galleries proceed, established succe ively on a level with the stories thus raised over one another. See fig. 730. The following objects may be specified in the figures :— a a , the first cuts filled up with rubbish, upon the first story E F , fig. 729. b b , other cuts subsequently filled up, upon the same story. c , the cut actually working. d , the front of the cut, or place of actual excavation of the mineral deposit. e , ma es of the barren rock, reserved in the cutting, as pillars of safety. f , galleries, by means of which the workmen may turn round the ma e , in order to form, in the roof t , an excavation in the direction of the deposit. g , rubbish behind the ma e . k k , two shafts leading from the first story E F , to the upper stories of the workings, as already stated. m , the wall, and t the roof of the mineral bed. In the second story E ′ F ′, the gallery of prolongation F ′, figs. 728. and 730. , is not entirely perforated; but it is further advanced than that of the third story, which, in its turn, is more than the gallery of the fourth. From this arrangement there is produced upon fig. 730. the general aspect of a working by reversed steps. Whenever the workings of the cuts c in the first story are finished, those of the second, a′ a′ , may be begun in the second; and thus by mounting from story to story, the whole deposit of ore may be taken out and replaced with rubbish. One great advantage of this method is, that nothing is lost; but it is not the only one. The facilities offered by the system of cro workings for disposing of the rubbish, most frequently a nuisance to the miner, and expensive to get rid of, the solidity which it procures by the banking up, the consequent economy of timbering, and saving of expense in the excavation of the rock, reckoning from the second story, are so many important circumstances which recommend this mode of mining. Sometimes, indeed, rubbish may be wanted to fill up, but this may always be procured by a few acce ory perforations; it being easy to establish in the vicinity of the workings a vast excavation in the form of a vault, or kind of subterraneous quarry, which may be allowed to fall in with proper precautions, and where rubbish will thus accumulate in a short time, at little cost. IMG:4147767755307473660_illo0849a.png:Bleyberg mine Fig. 731. represents a section of the celebrated lead mines of Bleyberg in Carinthia, not far from Villach. b , c , is the ridge of the mountains of compact limestone, in whose bosom the workings are carried on. e , is the metalliferous valley, running from east to west, between the two parallel valleys of the Gail and the Drave, but at a level considerably above the waters of these rivers. f g , is the direction of a great many vertical beds of metalliferous limestone. On considering the direction and dip of the marly schist, and metalliferous limestone, in the space w , w , to the west of the line 1, s , it would appear that a great portion of this system of mountains has suffered a slip between 1, s , and a parallel one towards the east; whereby, probably, that vertical position of the strata has been produced, which exists through a considerable extent. The metalliferous limestone is covered to a certain thickne with a marly schist, and other more recent rocks. It is in this schist that the fine marble known under the name of the lumachella of Bleyberg is quarried. The galena occurs in the bosom of this rock in flattened ma es, or blocks of a considerable volume, which are not separated from the rest of the calcareous beds by any seam. It is accompanied by zinc ore ( calamine ), especially in the upper parts of the mountain. Several of the workable ma es are indicated by r , r 3 ; each presents itself as a solid analogous to a very elongated ellipse, whose axis dips, not according to the inclination of the surrounding rock, but to an oblique or intermediate line between this inclination, and the direction of the beds of limestone; as shown by r w , r′ u . Every thing indicates the contemporaneous formation of the limestone, and the lying beds of the lead ore. The accidents or faults called kluft ( rent ) at Bleyberg are visible on the surface of the ground. Experienced miners have remarked that the rich ma es occur more frequently in the direction of these accidents than elsewhere. It is in general by galleries cut horizontally in the body of the mountain, and at different levels, s , g , s f , that the miner advances towards the ma es of ore r , r 3 . Many of these galleries are 500 fathoms long before they reach a workable ma . The several galleries are placed in communication by a few shafts, such as t ; but few of these are sunk deeper than the level of the valley e . The total length of the mines of Bleyberg is about 10,000 yards, parallel to the valley e ; in which space there are 500 conce ions granted by the government to various individuals or joint stock societies, either by themselves or a ociated with the government. The metalliferous valley contains 5000 inhabitants, all deriving subsistence from the mines; 300 of whom are occupied in the government works. Each conce ion has a number and a name; as Antoni, Chris toph, Matthæus, Oswaldi, 2, 8, 36, . IMG:4147767755307473660_illo0849b.jpg:Idria quicksilver mine Fig. . 732 is a section in the quicksilver mine of Idria. 1. is the gray-limestone; 2. is a blackish slate; 5. is a grayish slate. Immediately above these transition rocks lies the bed containing the ores called corallenerz , which consist of an intimate mixture of sulphuret of mercury and argillaceous limestone; in which four men can cut out, in a month, 2 1 ⁄ 2 toises cube of rock. IMG:4147767755307473660_illo0849c.png:Mansfeldt copper mine Fig. 733. represents a section of part of the copper mine of Mansfeldt; containing the cellular limestone, called rauchwacke , always with the compact marl-limestone called zechstein; the cupreous schist, or kupferschiefer ; the wall of grayish-white sandstone, called the wei e liegende ; and the wall of red sandstone, or the rot he liegende . The thin dotted stratum at top is vegetable mould; the large dotted portion to the right of the figure is oolite; the vein at its side is sand; next is rauchwacke ; and lastly, the main body of fetid limestone, or stink stein . IMG:4147767755307473660_illo0850a.jpg:Mansfeldt copper mine Fig. 734. represents one of the Mansfeldt copper schist mines in the district called Burgoerner, or Preu hoheit. 1. Vegetable mould, with siliceous gravel. 2. Ferruginous clay or loam. 3. Sand, with fragments of quartz. 4. Red clay, a bed of variable thickne as well as the lower strata, according as the cupreous schist is nearer or farther from the surface. 5. Oolite ( roogenstein ). 6. Newer variegated sandstone, ( bunter sand stein ). 7. Newer gypsum; below which, there is 8. A bluish marly clay. 9. Stinkstone, or lucullite. 10. Friable grayish marl. 11. Older gypsum, a rock totally wanting in the other districts of the mines of Rothenberg; but abounding in Saxon Mansfeldt, where it includes vast caverns known among the miners by the name of schlotten , as indicated in the figure. 12. The calcareous rock called zechstein . The lower part of this stratum shows symptoms of the cupriferous schist that lies underneath. It presents three thin bands, differently modified, which the miner distinguishes as he descends by the names of the sterile or rotten ( faüle ) rock; the roof ( dachklotz ); and the main rock ( oberberg .) 13. Is a bed of cupriferous schist ( kupferschiefer ), also called the bitumino-marly schist, in which may be noted, in going down, but not marked in the figure :— a , the lochberg , a seam 4 inches thick. b , the kammschale , 1 ⁄ 4 of an inch thick. c , the kopfschale , one inch thick. These seams are not worth smelting; the following, however, are :— d , the schiefer kopf , the main copper-schist, 2 inches thick. e , a layer called lochen , one inch thick. 14. The wall of sandstone, resting upon a porphyry. IMG:4147767755307473660_illo0850b.png:Kiegelsdorf mine Fig. 735. is a section of the mines of Kiegelsdorf in He ia, presenting — 1. Vegetable mould. 2. Limestone distinctly stratified, frequently of a yellowish colour, called lager hafter kalkstein . 3. Clay, sometimes red, sometimes blue, sometimes a mixture of red, blue, and yellow. 4. The cellular limestone ( rauhkalk ). This rock differs both in nature and position from the rock of the same name at Mansfeldt. 5. Clay, usually red, containing veins of white gypsum, and fine crystals of selenite. 6. Ma ive gypsum of recent formation. 7. Fetid limestone, compact and blackish gray, or cellular and yellowish gray. 8. Pulverulent limestone, with solid fragments interspersed. 9. Compact marl-limestone, or zechstein , which changes from a brownish colour above to a blackish schist below, as it comes nearer the cupreous schist, which seems to form a part of it. 10. Cupreous schist ( kuperschiefer ), of which the bottom portion, from 4 to 6 inches thick, is that selected for metallurgic operations. Beneath it, is found the usual wall or bed of sandstone. A vein of cobalt ore a , which is rich only in the grayish-white sandstone ( wei e liegende ), traverses and deranges all the beds wherever it comes.