in ancient mythology, was a goddess worshipped by the Romans under that name, and by the Greeks under that of Athene, or Pallas Athene. According to the earliest traditions among the Greeks, Athene was the daughter of Zeus. Homer says nothing of the mode of her birth; but Hesiod and other authorities say that she sprung from the head of Zeus after that god had swallowed his wife Metis. Various other legends concerning the origin of Athene were afterwards current, which arose, in all probability, from local traditions, or from the identification of the Greek Athene with similar deities of foreign nations. In the Greek religion Athene seemed to represent the union of power and wisdom. Thus she appears in Homer as the patroness and protectress of all those heroes who were distinguished for wisdom or courage, such as Achilles, Ulysses, Diomed, and others. She is likewise represented as the deity of agriculture, and the giver of the olive to the citizens of Athens, the city called after her name; as the inventress of all sorts of arts and contrivances; as the protectress of cities and states; and the upholder of law and order. Although a warlike deity, she was not regarded, like Ares, as bloodthirsty and delighting in war for its own sake; but rather as succouring and encouraging the defenders of the righteous cause, and as resisting and checking the mere brute strength of the god of war. The Roman goddess Minerva, who was identified with the Greek Athene, was represented as possessed of the same attributes. Her name seems to be derived from the same root as mens and monere. Minerva accordingly appears as the impersonation of wisdom, learning, and mental power. In Rome she was worshipped as one of the three Capitoline deities, and a festival was celebrated in her honour on the 19th of March, called Quinquatria or Quinquatrus, on account of its taking place on the 5th day after the Ides of that month. Minerva was also believed to have been the inventress of numbers; and a nail was annually driven into the wall of her temple to mark the number of the years. To this virgin deity calves untouched by the yoke were sacrificed, and the spoils of war were often dedicated. Minerva is generally represented as an armed virgin of masculine mould and majestic bearing, with sky-coloured eyes and an earnest countenance, wearing a plumed helmet on her head and an agis round her breast, and holding in her right hand a spear, and in her left the round Argolic shield faced by the petrifying head of Medusa.
MINES AND MINING.
The object of the present article is to present a view of British mines, the practice of mining in general, based upon the methods pursued in Cornwall and other mining districts of Britain, and to furnish accurate and recent statistics of the produce of our mines as well as their progress. Previous to these particulars, brief notices will be given of some principal facts concerning mineral veins and deposits, British and foreign, the rocks in which they are found, and the circumstances affecting their course and productiveness. Under the heads of the several metals will be grouped these and similar facts, and descriptions of the most important mining countries and districts abroad, with such statistics as can be obtained concerning them.
MINERAL DEPOSITS, VEINS, AND THEIR PHENOMENA.
Mining, strictly speaking, is limited to large and deep excavations of metallic deposits, like those of Cornwall, the Hartz, and other well-known metalliferous districts; but the term is sometimes improperly applied to the washing of alluvial deposits, such as those in which gold is frequently found. In our own country, in some parts of Cornwall, tin has been found included in gravel and similar diluvial matter. Small pebbles of tin, called "tin stones," have occurred under the surface, covered with gravel, clay, sand, or peat, which had to be removed before the rock was reached upon which the tin stones rested. The collecting and separating of these grains and stones is named "streaming for tin," because the covering gravel or other matter is cast upon an inclined plane over which a fall or stream of water is carried, and the whole mass agitated, so that the heavier tin stones remain upon the inclined plane while the lighter stones and earth are washed away. Tin streamworks are now of little importance, and are chiefly conducted by poor persons for small gains.
Some minerals, as iron, are found in beds rather than in veins. The ironstone beds of the coal measures in our country are very extensive and valuable. They supply the greater portion of the iron produced in Great Britain—the remainder being chiefly furnished by the beds and veins of haematite in the mountain limestones of Lancashire, Cumberland, Durham, the Forest of Dean, Derbyshire, Somersetshire, and South Wales. The beds at Ulverstone, Whitehaven, and the Forest of Dean are more extensively worked than any of the others, and appear to be inexhaustible. The older works of Devon and Cornwall likewise contain many veins of black haematite. The brown haematin also of the north of England merit particular attention. They contain from 20 to 40 per cent. of iron, and are found associated in large masses with the lead veins of the lead-mining country; and occasionally they are seen in distinct and regular beds. They exist as "riders" to the vein, but sometimes they compose its entire mass, and then attain a width of 20, 30, and even 50 yards.
Scientific mining is almost entirely confined to the exploration of mineral veins, or "lodes," as they are termed in Cornwall. It is not a work of difficulty or science to lay open and remove minerals deposited either in alluvial deposits or in regular and massive beds, but it requires much skill, patience, experience, and capital, to explore an important lode of copper, or tin, or lead.
Mr W.J. Hemwood gives an account of Cornish lodes Veins as follows:—"The lodes may be described as quartzose portions of the rock highly inclined, and of no great thickness, which are more or less mixed with metals and their ores. They have commonly one prevailing direction, subject to slight irregularities and curvatures as well in length as in depth, and traverse granite, slate, and porphyries indiscriminately, and almost always without other interruption than what may take place from their interferences with each other, and with the cross-courses, flutings, and slides (interruptions technically so named in Cornwall). But notwithstanding the workings of adjoining mines have often been extended for a considerable distance on lodes in the same directions, it is not at all certain that the same lode has ever been traced for more than about a mile in length. In fact, they invariably throw off into the containing rock shoots, strings, and branches, in such abundance, that instead of one champion-lode (as the larger lodes are provincially called), the whole forms a complex and irregular net-work of veins. Often, too, the lode first discovered dwindles to a mere line, whilst some of its offshoots swell out, enlarge, and rival, or even surpass, both in size and richness, the vein from which they have been separated. It is, however, rather more frequently the case that the lodes split as they go eastward, than the contrary. It is by no means uncommon for lodes to split directly at the point of their inter- Mines and section by a cross-course or flucan, on one side of which the lode appears in two branches, whilst on the opposite but one occurs." (Transactions of the Royal Geological Society of Cornwall, vol. v.)
The metallic parts of a lode do not form regular lines of metal running through the whole extent of the lode, but they occur in what the miners call "bunches," or in patches of various sizes and shapes. These very rarely occupy the whole space between the sides (or "walls," or checks) of a lode, even when the lode is rich and of tolerable width, but they are commingled with a variety of other substances, the principal of which is quartz. The vein named Gregorius at Freiberg is composed of nine layers, which may be thus represented:
| Wall. | Gneiss rock. | |-------|-------------| | 1 | 2 | | 3 | 4 | | 5 | 6 | | 7 | 8 | | 9 | |
From this it will be seen that the proportion which the metallic parts bear to the other parts of a vein, even in favourable instances, is not so large as might be imagined. One important department of mining, therefore, is to separate, as far as can be effected by mechanical means, the foreign substances from the metallic portions of the lode, as the two must be brought to the surface together. This mechanical separation gives occupation to women and children, in "dressing" the ores on the "dressing-floors" of the mines, and renders necessary a considerable amount of dressing machinery, as "stamps," "crushing mills," "jigging machines," &c., which are briefly noticed under the heads of Copper, Tin, and Lead.
The lodes of Cornwall have no determinate size, being sometimes very narrow, and at others exceeding several fathoms in width. Sometimes they extend to a great length and depth, or they terminate after a short course; and they are continually varying in breadth. Certain portions consist of a mere line between the walls or "cheeks" of the lode, while portions have been met with not less than from 30 to 40 feet wide. Such extremes are not common in the same lode. Occasionally, when a vein expands it becomes poor; but instances are known where the thickest part of a lode is also the richest part. There are masses of iron ore in Piedmont 350 yards thick; and the great open mine at Falun in Sweden is half a mile long and several hundred yards wide; but these are extraordinary examples. The distance for which lodes range along the surface of a country appears to have some reference to the magnitude of the disturbing forces affecting the district. A certain vein in Chile is 9 feet thick, has been proved for 90 miles, and is accompanied by branches 30 miles in length.
The lodes commonly occur in a position nearly vertical. Their inclination seldom diverges from the vertical to more than 10° in the north of England lead district; in Cornwall it averages much more (in some cases 70°), yet it does not often exceed 45°; while in many foreign mining countries it is inconsiderable. The inclination of a lode to the horizon is called its dip, or underlie, or hade, in the language of miners, and its intersection with the surface, the strike, which determines what is termed its direction.
In every mining district there are what are called systems of mineral veins, each system being characterized by some peculiarities of position or contents; and each appears to be referable to a distinct period of formation. Werner observed eight such systems at Freiberg, and the Mines and same number has been noticed in Cornwall. The first Mining class appear to have been earliest formed, and constitute a very large majority of the whole number in the district. They are the older tin veins, underlie to the north, and are traversed by those of the second class, which are comparatively few in number and of little importance. These two classes include all the lodes from which tin is extracted. Their breadth varies from a mere string to as much as 30 feet, and most of those which are productive range east and west. The third class are the east and west copper lodes, and these form the greater number of all the copper lodes in Cornwall. They always cut across the tin lodes when the two kinds meet, and they are usually accompanied by small veins of clay. The fourth class comprehend the contra (or counter) copper lodes, and they are few in number. Their direction is N.W. and S.E., or at right angles to those bearings. The fifth class contain the cross-courses, which run due N. and S., or nearly so, and contain no tin or copper, and only a little lead occasionally. They are rather wide, and have been traced on the surface for considerable distances. The remaining three classes are chiefly of importance as adding to the accumulation of facts respecting mineral veins.
It is a long observed fact, that in almost every case in Direction Cornwall the productive veins run E. and W., and the cross-courses N. and S. The more recently filled fissures and partings are composed almost wholly of clay; so that, as a general rule, veins which contain a great quantity of this clay traverse those which contain a smaller quantity.
In the Freiberg (Saxony) districts, as described by Werner, we find a number of mineral phenomena somewhat analogous to those observed in Cornwall, but the metals are different, as also are the prevailing directions of the lodes; the first and most ancient running chiefly N. and S., and including those veins from which the chief supplies of lead and silver have been obtained. The contra lodes are more argentiferous, but much thinner, and their direction is about N.E. and S.W. The veins of the third system are all N. and S., and those of the fourth at right angles to them, corresponding to the Cornish cross-courses. They both contain lead glance. The lead veins of the north of England and Derbyshire are much simpler than those lodes of Cornwall or Saxony. The direction of the lead veins is almost invariably E. and W., and they are traversed by non-productive cross-courses at right angles to them.
A number of perplexities arise out of the various intersections of lodes by one another; and it is obvious from what has been said, that such intersections in a mining county like Cornwall will be frequent and sometimes complicated. A lode intersected horizontally is sure to be heaved, and the consideration of all the points connected with heaves would comprehend—(1.) the composition of the intersected vein; (2.) the composition of that intersecting it; (3.) the nature of the containing rock; (4.) the widths of the intersected and intersecting veins; (5.) their horizontally-inclined angles; (6.) their inclinations; and (7.) the extent of the heaves at different depths. Again, the determination of these questions would apply equally to—(1.) the intersection of lodes by cross veins; (2.) the intersection of cross veins by lodes; and (3.) the interferences of lodes with each other. Without entering into these points of inquiry, we may notice that some general laws may be deduced from the average of a great number of observations. Vertical intersections, or leaps, or throws, require similar study, as to—(1.) the nature of the intersecting vein; (2.) the vein intersected; and (3.) the influence the angle at their intersection may have in the direction or distance of the leap or throw. In no instance of vertical intersections has the same vein been seen to intersect another more than once, or to interfere with more The practical object of all researches into the course and structure of lodes is to ascertain, if possible, their general laws, so that the miner may follow their course, may retrace them when dislocated and thrown out, and especially determine what circumstances influence their richness in ore. A few circumstances only of the latter kind are generally recognised, while many others which have been received by some miners are subject to numerous exceptions. We may notice one or two of those generally approved. An old proverbial saying is, "ore against ore,"—arising from the fact that whenever a lode is rich, if there be another lode near it having nearly the same direction and in nearly the same country, whatever be the rock, the second lode will probably be found rich in that part which is opposite to the rich part of the first lode. The proverbial phrase "ore against ore" has been acted upon from an early period.
Another fact is, that when elvans (porphyritic veins) and tin and copper lodes occur together, they are found in connection, as a whole, with good mines. Most of the ore in the principal mines in the Gwennap district of Cornwall have been found in or near large elvan courses. Not a few of the larger and wider bunches of ore, both tin and copper, have occurred in the immediate vicinity of cross-courses and elvans, and frequently also exclusively on one side of their intersections. It has been generally thought that depth below the surface is influential on the quantity and quality of the ore contained in the veins. It is confirmed by several observations, that mineral veins are generally richer near the surface than at great depths. It is a common opinion in Cornwall that copper, on the whole, occupies greater depths than tin. "At about 80 or 100 feet under the surface the first traces of copper or tin are found; rarely nearer to it than 80 feet. If tin be first discovered, even without a trace of copper, it is not unusual that in the course of sinking 80 or 100 feet or more, all trace of it is lost, and copper only is found. But if, instead of tin, copper be first discovered at a depth of 80 or 100 feet, tin is seldom or never found below it in the same vein." Such was the opinion of Phillips the mineralogist; yet tin is sometimes found 100 feet deep without a trace of copper, and there are many instances of tin ore accompanying copper ore to a great depth,—in one case 200 fathoms below the surface, and even under the copper. The meeting of two lodes, either vertically or horizontally, is generally considered a sign of richness, more particularly when the angle at which they meet is small or not very great. It is also a remarkable fact, that in every lode, whether it yields tin, copper, or lead ore, the portions which are the most perpendicular are the most productive.
In Cornwall the mean breadth of tin lodes is about 3'06 feet, of copper lodes about 2'93 feet, of lodes containing both metals about 4'7 feet; and this greater average breadth of lodes, including a mixture of copper and tin, is found in any rock and at any depth. Generally a diminution of the width of a lode is a precursor of poverty. The average breadth of lodes at less than 100 fathoms deep is 3'97 feet; at more than 100 fathoms deep it is but 3'36 feet.
The limits of mining districts are often very decided geologically, and are also marked by peculiar physical features. The neighbourhood of Cross Fell, in the north of England, has been worked with the greatest enterprise, but no instance has occurred of a single vein being traced across the great Penine fault to the west. Similar facts have been observed with respect to the Flintshire veins of lead, occurring in the Carboniferous limestone, and which in no instance enter the Silurian rocks. In this instance, and in many others, the older rocks seem to rise on the line of a great axis of disturbance, and to cut off the whole of the mining ground, as if nature itself marked out the mining districts and set bounds to them.
As a general rule, with some important exceptions, particular metalliferous deposits have affinities for particular rocks or geological formations. Iron at once occurs as an important exception to this rule, for it is found, to speak only of our own country, in the older rocks of Devon and Cornwall. Magnetic oxide and specular iron occur in the granite of Dartmoor. The New Red Sandstone, in its lower measures, yields beds of haematitic conglomerate. Important beds of iron are worked in the Lias and Oolites. The greensands of Sussex once furnished a large amount of iron to the ironworks, and recently the greensands of Wiltshire have shown indications of large deposits. But while iron is a marked exception, we shall find the rule hold good in relation to other metals. Thus tin is most plentiful in granite, and the rocks lying immediately above it. Copper is found in various slate formations, and in the Trias of geologists; but it is not generally met with in strata more recent than the Old Red Sandstone, although there are in England some exceptions. The celebrated Ecton Mine in Staffordshire, and the Llandudno or Orme's Head Mine in Caernarvonshire, are situated in the Carboniferous limestone. On the Continent copper is mined in a formation still more recent,—viz., the copper-slate of Thuringia, which forms a portion of the New Red Sandstone series. In Cornwall it prevails in the clay slates (killas), although one of the most profitable mines in Cornwall (Treasevan) is worked in granite. Lead has a marked affinity with the mountain or transition limestone, as is evident in Derbyshire, Yorkshire, Northumberlandshire, Durham, &c.
There are also other indications of preference more specific even than particular formations. For instance, while copper is found both in granite and slate rocks, the most productive mines are almost invariably situated just upon the junction of these two formations. Experience in Cornwall has shown that no continuous or very abundant supply of this metal is to be expected in any spot far removed from the line of junction. In the serpentine rocks of the Lizard, copper of great purity has been discovered, principally in masses.
The accumulated evidence from all parts of the mineral world proves that the contents of the veins depend on the peculiar character of the rocks they traverse. Although this is an acknowledged truth amongst geologists and miners, yet the ignorance or neglect of it has led to numerous practical mistakes. It has been supposed that because veins were rich in one place, the continuation of the same veins must be a continuation of the same riches. But if the veins intersect unproductive rocks, the riches come to an end. The public are often deceived by a plausible project which is brought forward on the strength of the ground being near a very prosperous mine. Works have been carried on at great expense in unproductive ground without a chance of success, simply because the lode happened to be in the same direction as in a neighbouring rich mine.
The mineralogical modifications, therefore, of the various rocks in metalliferous districts, very commonly bearing the same names, are subjects of careful examination by intelligent miners. When the rocks present certain characters, not perhaps noticed even by geologists, miners find their chances of success increased or diminished. In Cornwall and Devon they prefer a granite or porphyry (elvan) which is to some extent decomposed. Other signs are carefully noticed; so that an experienced miner will at once pronounce whether the "country is kindly" or not for copper or tin. Several instances might be adduced to Mines and strengthen these views. The principal lode in Fowey Mining. Consols Mine affords a good example of ore accompanying a particular set of rocks, and it is found that the "bunches" of ore occur in certain directions. In Godolphin the lodes were rich where the killas (argillaceous slate) was of a bluish-white colour, but poor when it was black. In Police and Huel Fortune the lodes in the killas continued productive until they entered a stratum of blue, hard killas, which cut out the riches. At Penstruthal Copper Mine the lode had been tried unsuccessfully at various times in parts where the granite was hard; but trial being made where that rock was soft, it became one of the most profitable mines in Cornwall. In other countries we find indications of similar phenomena. In Upper Hungary the largest copper lodes are found in fine gray slates; in Saxony the silver ores occur in gneiss; and in the Hartz certain ores are intimately connected with the graywacke. At Andreasberg the veins which pass from argillaceous slate into flinty slate lose their riches in the latter. The Wenzal vein at Fürstenberg runs nearly vertically from north to south across many beds of gneiss about 60 feet thick, dipping east, and each of these beds forms a distinct variety of rock. In the first bed the vein formed a nearly imperceptible string of clay; in the second it became 12 or 18 inches thick; in the third the thickness of the vein is preserved; in the fourth the silver ores, which had disappeared in the third, become as abundant as they were in the second, but they gradually disappear in depth. The vein is shifted in depth to the westward by several cross-courses, and between two of these it becomes very rich.
THE PRACTICE OF MINING.
From the manner in which mineral accumulations have been deposited in the earth, it is evident that mining operations must be of two very different kinds. Thus coal, salt, many ores of iron, and some of other metals, appear in regular layers interstratified with and forming part of the series of deposits which make up the earth's crust at particular places; while the usual ores of tin, copper, and lead occur in crevices formed in rocks after they have been deposited, and often since their subsequent metamorphosis.
Discovery. If mineral veins are to be sought for in any unexplored or but partially explored district, the geologist can predict favourably or unfavourably, according to the nature of the strata, but he can only predict. The practical miner can give his opinion whether the "country" (or rocks) be "kindly" or not for metallic veins. One course, however, of a surer nature can be also adopted, that of shodding—an old term by which is signified the search for loose masses of ore of all sizes, either in or under the upper soil, sometimes upon the top, basset, or outcropping of the vein, but more frequently a little to the lower side where there is a declivity, and where the vein crosses the slope. This shode ore, varying from the size of a pea to large pieces, is produced by the weathering or decomposing of the sides of a vein, causing the ore to stand higher than the superficies of the rock, which in time slides off where the ground is sloping. Miners who go out shoding will traverse rivulets, gullies, scours, and other similar places where the surface of the ground is broken, or where the strata rise up to the grass roots; and they will even examine newly-ploughed lands and molehills. Shode ore being found upon a slope, or at the foot of it, the finder must look diligently for other signs of a vein, and then circumstances in each case will determine how a trench may be best opened towards the vein. A number of trial pits may be sunk, and other means of a like character may be adopted to prove the presence and character of the supposed vein.
Another similar course is to search for what is called float-ore, or that which has been floated down by water acting upon the veins of ore. Hushing is the employment of Mines and a reservoir of water on a height, so as, by due direction downwards, to wash out pieces of metalliferous stone. If a quantity of water can be thus conducted down a slope, it will clear the superficies of the rock, wash and clean all the veins showing themselves at the surface, and often lead to a valuable discovery. Frequent applications of water will wear a channel to some depth without diggings which may or may not be subsequently employed.
Many lodes, however, afford no shode; for if the upper part of the lode contains no ore, or the detritus is carried too far, or is too minutely subdivided, there is no metallic indication to guide the miner. He may indeed meet with pieces of gossan (a hydrated peroxide of iron), which is always considered an indication of metal being near. Where gossan prevails it has been generally found that copper ore is connected with it. But the mode of search adopted where there are no shades or gossans is that which is provincially named "costeaming," a word which literally means fallen-tin. The process consists in sinking small pits through the superficial deposits to the solid rock, and then driving from one pit to another across the direction of the vein, in such manner as to cross all the veins between two pits. The pits are often sunk several feet in the rock before the communications between them are made. It is necessary to the success of costeaming that the miner should have made out the prevalent strike of the principal systems of right-running veins in the district. In cases where the rock is not extremely hard, and is not thickly covered at the surface, open cuttings may be made at a small cost, which will lay the lodes bare for some distance. But the circumstances of the locality must determine or modify the attempts at discovery.
We have named gossan as a favourable sign, and it may be added, that in certain districts, and with certain classes of veins, there is so large a quantity of iron present that the decomposition of this metal near the surface makes itself manifest in ferruginous stones; and the tops of many of the lodes, when found near the surface, are frequently cavernous and abound with gossan. So much importance do Cornish miners attach to it, that they consider no large vein to be of much value without this accompaniment. A similar decomposed ore is named by the German miners eiserne hut and eisenkopf, and by the French chapeau de fer. But although these occurrences and names point to a prevailing feature, yet it is quite erroneous to apply this to all mineral veins, for in some valuable districts scarcely any iron exists, and therefore gossans and ferruginous indications are wholly wanting. The opinion may hold good for Cornwall, where gossan abounds and often extends to as much as thirty fathoms below the surface. It is of no value in itself; but attention has of late years been drawn to it on account of small amounts of gold associated with it, generally a few pennyweights to the ton. It was thought that by the use of Berdan's machine, and other apparatus, the gold could be profitably extracted, but after operating on large quantities, this hope has been disappointed. Gossan also contains silver in small quantities, and operations are sometimes successfully carried on for extracting it. Argentiferous gossans sell at from forty shillings to forty pounds per ton. They are bruised to small pieces and sent to the smelting works, where they are mixed with certain proportions of lead ore of low average for silver. The two are then melted together and run out into pigs, which undergo further processes.
When the position of a mineral vein is ascertained, and some conjectures have been hazarded, from various signs, concerning its extent, course, thickness, and value, the work of mining properly begins. Shafts must be sunk and levels (galleries) must be driven to prepare the way for the extraction of the ore, and at the same time to carry off the Mines and water which either flows into the mine from springs, or drains into it from the surrounding strata. Two sets of galleries must be driven at right angles to each other, and both horizontal, one being in the direction of the strike of the vein, and the other at right angles to that direction. If we suppose a simple instance in which the mineral veins crop out at the sides of a hill, and follow a direction on the whole uniform, we may illustrate the proceedings by the subjoined figure, in which two lodes of moderate thickness (A and B) are seen.
A shaft must be sunk to reach the vein at a certain depth, but it will depend on the direction of the dip or underlie of the lode,—whether towards or from the valley or slope of the hillside,—and on many similar circumstances, as to where it will be most desirable to commence the sinking. With reference to the lode A, a cross-cut (1) may be driven at the lowest convenient point above the level of the highest water of the valley, and this gallery, having a gentle slope from the lode towards the hillside, will form the adit-level, and be the channel through which the whole drainage of the works will be carried; while it may also serve to convey the ore that is obtained out of the mine. With reference to the lode B, the driving of an adit-level will offer similar advantages, but there is a difference in the arrangement of the shafts. In both cases it is found advisable to sink shafts upon the upper side of the vein, but in B it is also convenient to have a sinking (3) towards the slope of the valley, and which does not cut the lode itself.
Although a perpendicular shaft has many advantages, and is almost always adopted in coal-mining, where extractions are carried on; yet in metallic mining, such a shaft is not in every case employed. Shafts are occasionally commenced at the outcrop, and, where the inclination is not very considerable, are continued in the substance of the vein itself; but in a slanting shaft the difficulty of raising the ore is much increased, and many practical reasons often render it expedient to sink at some distance from the outcrop, so as to meet the lode at a convenient depth.
The labour of sinking shafts in hard rocks like the Primary is very great, and the cost very considerable. From the records of shaft-sinking in Cornwall we may instance some cases showing the slowness of the descent, arising from the hardness of the rock. At one mine only 20 fathoms, or 120 feet, were sunk from 1828 to 1834, being at the rate of between 3 and 4 fathoms per annum. In Levant Mine, from 1830 to 1837, 90 fathoms were sunk, or at the rate of 13 fathoms per annum. In East Wheal Crofty Mine 77 fathoms were got through in the time between 1833 and 1837, amounting to 14 fathoms per annum. A sinking, therefore, of 1 fathom, or 6 feet per week, has sometimes been all the progress that could be made. To avoid the delays that must necessarily occur in sinking at this rate, a plan has been adopted in Cornwall of excavating several portions of a shaft simultaneously, by operating at different levels at the same time, which of course can only be done in a mine already opened, and requiring additional shafts. The great feat is to excavate the several Mines and portions so accurately, that when they are finished they may all exactly fit into each other, and form one perfect and perpendicular shaft. One party will work from the surface, another from one of the upper levels, and a third from the lower levels, simultaneously.
Remembering the slow course of excavation in hard rocks, the depth to which some of the Cornish mines have attained is truly wonderful. Rather more than 20 years ago, Wheal Abraham Mine had reached the depth of 242 fathoms, or 1452 feet. Dolcoath Mine had reached 235 fathoms. The Consolidated Mines are 300 fathoms, or 1800 feet deep, and the United Mines 280 fathoms below the adit-level. Tresavean has gradually attained an extraordinary depth; and it was lately reported to the writer by Robert Were Fox, Esq., as being 320 fathoms, or 1920 feet deep below the adit-level, 2112 feet below the surface, and about 1700 below the level of the sea. To realize these depths, the reader may note the height of any lofty public monument or church spire with which he is acquainted, and, standing at its base, multiply in his mind the height of the object in sight by the number of times requisite to reach the depth of one of these mining shafts. Thus, for example, the height of St Paul's in London is said to be 340 feet; now the depth of Tresavean Mine is more than five times, or nearly six times, the height of St Paul's. The shaft of the Monkwearmouth Coal Mine near Sunderland is 1590 feet clear perpendicular depth, which is equivalent to the piling of the Monument of London seven or eight times upon itself. In one mining tour amongst the collieries of the north of England, the writer of this article descended twelve shafts, the aggregate depth of which was no less than eleven thousand seven hundred and eighty feet. One of these was the Monkwearmouth shaft first named. The mode of descent was (at that time) by a large iron tub and wire-woven pit-rope. The lapse of time in descent was rather more than four minutes.
Some foreign metallic mines have been carried to great depths. The Eaelshacht Mine at Kuttenberg in Bohemia, now inaccessible, was deeper than any other mine, being no less than 3778 feet below the surface. That depth was only 150 feet less than the height of Vesuvius, and it was eight times as great as the height of the pyramid of Cheops or the cathedral of Strasburg. Mines on high ground may be very deep relatively to the surface, but not to the sea-level. The mine of Valencians, near Guanaxuato in Mexico, is 1686 feet deep from the surface, but 5960 feet above the level of the sea. For the same reason the rich mine of Joschimsthal in Bohemia, though 2120 feet deep from the surface, has not yet descended to the sea-level.
It is common to divide the shaft into two by a strong wooden partition running down the middle; and to sink several shafts when the mine is extensive. At the Carn Brea Mine, which extends superficially in length for a mile and a half, and in breadth for about three-quarters of a mile, there are from twenty to thirty shafts; and other mines have even more. Such shafts are often situated along the line of the lode, and they bear different names to distinguish them, as, perhaps, "Taylor's Shaft," "Dixon's Shaft," &c.
It very rarely happens that the lode is perpendicular, but its inclination as it descends is generally to the north. If the underlie is not great, the shaft may to a considerable distance follow the lode; but if it be great, the shaft descends, not in one continuous line, but, as it were, by a succession of steps. It will be sunk perpendicularly by several fathoms at a time, the lode meanwhile diverging from it to the northward; but at certain distances the sinkers pause, and horizontal courses are driven in the direction of the lode until it is again struck. Whenever Mines and the lode is struck the shaft is sunk again, and the lode is again to be reached by a horizontal course as before. Thus, while the shaft is being sunk, the horizontal passages of the mine are being constructed.
The adjoining figure is a vertical cross section of the shaft and lode, designed to show the course of operations in the simplest form. AB is the engine-shaft and CD is the lode. At every 10 fathoms of the sinking of the shaft a cross-cut c is driven to meet the lode CD. This process is repeated at every 10 fathoms until the shaft crosses the lode at 80 fathoms, where the direction of the cross-cuts c, c is changed from right to left to meet the lode, while the shaft descends perpendicularly as before. This simplest form of procedure may be varied to answer to the varied conditions and requirements of the lode.
What we mean by the levels of a mine will be understood by fig. 3. The levels are parallel courses which diverge on either side from the shaft, and follow horizontally the course of the lode. These courses are usually in Cornwall 10 fathoms, or 60 feet, apart. After the shaft is sunk 10 fathoms, the first level will be run; or, to speak in common language, a horizontal passage will be cut from either side of the shaft, following the direction of the lode. The dimensions of this passage are generally from 5 to 6 feet in height and about 3 feet wide. It is seldom made wider, unless the lode is very rich, and never much narrower, as this width is necessary to the working of the lode. But there is no limit to the length of the level, except the sett or bounds of the mine. Where the course of the lode is irregular, as it generally is, the levels will not be directly over and under each other, but may vary considerably according to the course of the lode, which necessarily governs the mining excavations.
The miner's tools consist of his pick and "gad" or wedge, and shovel, together with a series of blasting or shooting tools, such as sledge or mallet, borer, claying-box, needle or nail, scraper, tamping-pan; added to which are Mines and Mining powder-horn, tin cartridges, and safety-fuse. When blasting by gunpowder was introduced, great danger arose from premature explosions. The powder was placed at the bottom of the hole in the stone, when bored to a sufficient depth; the needle was then inserted, and the hole filled up with sand or clay, and rammed in perfectly tight. The needle being then withdrawn, and a rush inserted and ignited, the miner scrambled to a place of safety. But the iron needle, when struck with the mallet, would often give out a spark and explode the whole; a copper needle was therefore substituted for it about 30 years ago, which itself has been generally superseded by the invention of the safety-fuse, consisting of a small hemp cylinder well saturated with tar and filled with powder.
Besides horizontal galleries, what are termed winzes, or short shafts (see fig. 3) extending from one level to another, answer the purpose of making trial of the vein in the intermediate space between two levels, and by dividing the great masses into rectangular portions, these may be examined all round; so that the miner has the means of judging with tolerable certainty of the nature and value of the ores contained in each pitch, and can extract the produce in the most expeditious and economical manner, attacking these portions from as many points at once as may be convenient. By this arrangement, no necessity arises for breaking down the unproductive masses which are often found to intervene, even where the vein is richest and the ore most continuous. The vein having been properly laid open, the ore may be worked away round such unproductive masses, and these, when left standing, will form supports to the work on each side of the vein. Thus, for working out the ores, a system of winzes is quite as necessary as a system of levels; and as the levels are driven horizontally at vertical distances of 10 fathoms, so the winzes are sunk vertically at intervals of 20 or 30 fathoms; their position being so regulated as to prove the richest and most promising portions of the veins, and to avoid the harder and more unproductive portions.
Suppose that a continuous body of ore is met with in Pitches, one of the upper levels, and that winzes had been regularly carried down to the level below it, then similar operations will be required in the upper, and winzes will be sunk from it to the next lower level in the same manner as before; but they will generally be situated about midway between the former winzes, so that each may expose the ground under the middle of the rectangle formed by the upper winzes and the levels between which they are placed; and
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**REFERENCES**
A Biewett's Shaft, used as a ladder-road by those merely who work in 15 and 23 fathoms levels. B Prince's Shaft, used exclusively for drawing up the minerals. C Prince William Henry's Shaft, through which the greater part of the men descend to their different pitches and ends. D Prince's Shaft, used exclusively for drawing the minerals. E Duke's Shaft, through which the greater part of the men descend to their different pitches and ends. F Prince's Shaft, used exclusively for drawing the minerals.
The double line east of Pressure Shaft shows the junction of the counter with the main lode.
There is generally a strong current of air passing down Doctor's Shaft, which extends through the winzes and other shafts.
The shaded patches indicate the parts of the lode which have been already removed.
Fig. 3. [Scale of 10 Fathoms to 1 Inch.] Mines and in this way the vein will be effectually exposed with the smallest number of excavations. A reference to fig. 3 will make this apparent. The tendency of this plan is to divide the vein into solid rectangular compartments of dimensions varying in different systems. When finally subdivided into portions of about 10 fathoms in height and 16 in length, they form convenient pitches for the Cornish miners. These pitches are "set" or let out to the workmen by auction, as afterwards described. In course of time the result of the operation we have described will be a large mine, as illustrated in fig. 3, which represents a vertical section of North Roscar, on the main lode. The references attached to this plate will explain particulars, and briefly illustrate the entire working of the mine. It will be seen that from a main shaft such as E, at vertical descents of 10 fathoms, long and ever extending horizontal galleries (levels) run right and left. These are numbered in the section successively, according to their distances in descent from the adit-level. By this numbering the exact place in the mine of any level can be indicated; and the workmen speak of their place in the 30 or 70 fathom or other level. All the horizontal strong black lines in the plate represent the levels; the long perpendicular lines the shafts, variously named; and the short perpendicular lines the winzes.
To illustrate the mode of working out the rectangular pitches, the irregular procedure according to the character of the vein, and the progress of the excavations, a distinct view of one portion of a Cornish mine is displayed in fig. 4. The different shadings will also show what parts of the lode have been extracted, and what are in process of extraction. The "ground" or metalliciferous mass is removed by what is technically called "stoping." To stop is to excavate horizontally, or "to beat away the backs." The word stopes is evidently a corruption of step; and, in fact, the ore was taken away in steps. The French miners use the term gradins as synonymous with our word stopes. By the old miners the mass was invariably removed by the process of "under-hand stoping,"—the quickest, but the worst manner of getting the ore. The present method, or that adopted in the best mines, is termed "over-hand stoping." By this it is necessary, after having discovered ore, to sink shafts and drive levels before ore is attempted to be raised. No ore is raised before the ground is "laid open," and levels are excavated under the ore. Then stoping may be commenced over a level; the "deads" or rubbish may be piled up over the level, on a timber frame or "stull" (one only of which is necessary for each level by this plan, instead of several by the old plan); and the whole course of mining may be conducted so as to produce fair and average returns.
A current of air, commonly sufficient for ventilation, passes through the mine by descending the main shafts, coursing through the levels, and ascending by the winzes. But when the mine is far extended in the course of many years, the miners do not find adequate fresh air; and the increase of temperature, which is always proportionate to the increase of depth, to the number of workmen present, and to the more confined and remote position of the recesses, is so considerable, that a decidedly injurious result is occasioned to the health of the miners. An analysis of sixteen samples of air taken from four mines in Cornwall, at an average depth of 214 fathoms, and at an average distance of 28 fathoms from any shaft or winze, gave a mean percentage of 17°067 oxygen, 82°848 nitrogen, and 0°005 carbonic acid gas, instead of the normal proportions of 79 per cent. of nitrogen and 21 per cent. of oxygen. The mean temperature of the Cornish mines is generally higher than that of coal mines; and at a depth of 250 fathoms there is a difference of upwards of 10°. In many of the deeper parts of the Cornish mines the temperature approaches 100°; so that the miners have to plunge into water several times during their relays of painfully laborious work. The miners' health is thus injured; and the timber used to prop up the passages rapidly decays. These evil effects might apparently be avoided by the adoption of the Newcastle system of ventilation in coal mines, for which system the arrangement of Cornish mines offers peculiar facilities. (See a paper by H. Mackworth, Esq., in p. 28 of Twenty-first Report of the Cornwall Polytechnic Society, 1853.) The temperature of the deepest level in the Tresavean Mine was recently reported to the writer as 90° and upwards; and some of the water gushing into the deep level of the United Mines has been, says Mr Fox, from 105° to 108°.
Minerals were originally raised to the surface by the Methods of common windlass, and afterwards by a horse-wheel. A raising mill-water-wheel was next applied; and on the introduction of Newcomen's engine, the water expended was sometimes pumped up again by it. A water-wheel with double buckets succeeded, in order to reverse the motion, and alternately raise and lower the rope. This was improved by Smeaton, who retained the single buckets, but made the rope-roll to throw out of gear and reverse. A step further was to apply Watt's engine directly to the rope-roll by means of a crank. The Cornish bucket that contains the ore and stuff is called a kibble. An experienced mining engineer has known as much as L2 paid for drawing the same quantity of ore to the surface by horses as is now done by steam-power for one shilling. In raising ores the miners generally work upwards from the back or upper part of one level towards the bottom of another, and the excavations are so arranged that the ore may readily fall down to the level below them. The modes of bringing the ore, when dislodged, to the surface are various in different districts and countries. The most primitive and most disadvantageous method is, when ore is carried on the backs of the men or lads to the surface. Even women were employed at this degrading labour in Scotch coal mines before the investigations of the Mining Commissioners in 1840. An act of Parliament now excludes females from underground work. Very little ore is now carried on the backs of human beings in Britain.
The conveyance of ores along the level is effected by hurdles or barrows in some places, and by waggons in more advanced districts. The passage is facilitated by laying down wooden or iron rails, and thus forming subterranean railways.
In situations favourable to inclined planes, they are most convenient for the transport of ores to the surface. At Wheal Friendship Mine in Devonshire there were two inclined planes, distinguished as the old and the new, both beginning near the same point on the surface. The old was about 500 yards in length, and the perpendicular depth from the surface at the lower end was 600 feet; the angle formed with the horizon being about 20 degrees; but another plane is now in use, which is 630 yards in length, and attains to a perpendicular depth of about Mines and 1025 feet below its mouth, or 1100 below the surface.
Mining. The inclination which it forms with the horizon varies from 30 to 45 degrees—an angle which exceeds that of the inclination of the steepest mountain in this and probably in any other country; consequently no carriage could be propelled up so steep an ascent without the power of machinery. A single track of edge-rails is carried along the plane from top to bottom; and a wrought-iron waggon, loaded with ore, is propelled by the force of a large overshot water-wheel, 40 feet in diameter and 5½ feet in breast, which is turned by a considerable stream of water, conducted with another stream several miles through a leat or artificial channel to work this and other machinery belonging to the mines. The two streams constantly furnish 5000 gallons of water per minute.
A popular illustration of this inclined plane might be drawn from St Paul's in London. The height of St Paul's Cathedral, to the top of the ball and cross, is 340 feet. Supposing, therefore, that two buildings of equal altitude were placed on it, we should have an elevation of 1020 feet, answering nearly to the perpendicular depth of the foot of the inclined plane below its mouth, which was before stated as 1025 feet. If from this immense elevation we conceive two ropes or imaginary lines, about 4 feet apart, to be extended through the air, following the line of Ludgate Hill, and reaching the ground at the eastern end of Fleet Street, a distance of above 500 yards, the length and slope of the inclined plane will be nearly correctly realized.
The underground work of a well-managed mine will be of two kinds—(1.) Work for discovery or development; and (2.) Work for extraction of ores. We might distinguish these two kinds of work as dead and live work; the dead being that which proceeds in the dead rock, and the live that which is concerned in extracting the ores. The only fair and permanently successful plan of managing the interior work of a mine is to economize the supply of existing ores, so as in some measure to equalize it; and not to take out all the ore which could be immediately obtained. Masses should be left here and there only to be extracted as the general prospects of the mine may require. These should form a sort of reserve fund of ore, to which recourse may be had when less is raised from newly-discovered parts than the average. The ores thus reserved in various parts are expressively termed in Cornwall the eyes of the mine. They who take all the ore they can get out of a mine, without making proper reserves, are said to pick out the eyes of the mine. By picking out the eyes and sending them to market, a fictitious value has sometimes been imparted to shares,—a process analogous to that of some companies who have paid dividends out of capital. In all accounts of well-directed mines the reserves of ores are alluded to. Heavy expenses in works of discovery can only be profitably sustained by mining establishments of magnitude, which, by sending up a fair general amount of ores, can afford to appropriate a certain portion of the profit for discovery. The Fowey Consols Mine, Cornwall, has long been known as a good example of this management; and expenses have been there incurred for discovery which would have been ruinous if the mine had been divided into three or four separate adventures. The extraction of an extensive mine is very considerable, though by no means so large in mere quantity as that of an extensive northern coal-pit. At the Consolidated Mines, Cornwall, in good times, the daily extraction was about 200 tons, a large proportion of which was raised from a depth of from 200 to 300 fathoms (1200 to 1800 feet).
The extent as to space to which mines are worked depends upon their age, prosperity, and hardness or softness of rock. Success has more to do with the extent than mere age. When the success of discovery has been great, excavation has proceeded rapidly; and conversely. When that very prosperous recent mine, the Devon Great Consols, had been at work only five years, it was found (in 1850) that there were 5853 fathoms, or nearly 7 miles, of excavations, vertical and horizontal.
One of the most formidable obstacles met with in the progress of mining is that of accumulated waters. Water is lateral the arch-enemy of coal-mining in the north of England, and of copper-mining in the south-west. The copious springs tapped in sinking shafts near Newcastle have been the surprise of all who have encountered them. In that district they are termed feeders. In the sinkings at the Great Hetton Colliery, Durham, three principal springs or feeders were met with, of which the first issued 2000 gallons of water per minute, the second 1000 gallons, and the third 1600 gallons per minute. In sinking Hebburn Colliery, Newcastle, it was necessary to contend with feeders pouring out 3000 gallons per minute. At Haswell, Durham, an error in endeavouring to sink through a bed of quicksand occasioned an outlay of L60,000, and yet the attempt was abandoned for another spot not far off, where the quicksand was avoided. The feeders of water in the quicksand supplied the enormous quantity of 26,700 tons of water per diem, probably the greatest amount known, unless we except the Dalton or Dawdon sinking for the South Hetton Company, Durham, where similar feeders were encountered, and where 1300 horse-power in steam-engines was necessary to pump out the water only, sometimes at the rate of 10,000 gallons per minute. In that locality the cylinder of the engines is 84 inches in diameter. They are condensing and double engines, and amongst the largest and most powerful ever erected. In the Cornish mines, although situated in hard rocks, we find vast accumulations of water. They do not issue from feeders in sand, like those just described; nevertheless, the infiltration of the rain and surface water, together with subterranean streams and pools, would soon inundate a mine and put a stop to the work, were not adequate means employed to drain the mine. In some of these mines a great increase of water almost immediately succeeds the commencement of the heavy autumnal rains; in others, on the contrary, this increase, though equally certain, does not take place until after an interval of several months. The necessary inference is, that the increase is owing to the rain and surface waters which, being absorbed, sooner or later find their way into the deeper parts of the mine.
Wherever in mining the workings are driven below the natural means of drainage, or below the level of the plain, recourse must be had to mechanical means to remove the water. The quantity of percolating water is diminished as much as possible by planking, walling, or caulking up with the greatest possible care those pits and excavations which traverse the water-levels; and the lower workings are so arranged that all the waters may unite in wells (sumps) situated at the bottom of shafts or inclined galleries, whence they may be pumped up to the surface or to the level of the adit or gallery of efflux. In most mines simple sucking pumps are used, as they are less subject to give way, and are more easy of repair. As many of these are placed over each other as there are lengths of 10 yards in the shaft, below the point where the waters have a natural run. These means for draining are set in motion by that mechanical power which happens to be the least expensive in the
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1 The word adit is variously used in mining. It sometimes signifies a level taken up at the foot of a hill, and either driven on the side or to intersect it, for the purpose of draining the mine at that level. It is also occasionally used in bringing out the ores. The top adit is that first driven; the deep adit is that lowest driven; the air-adit, that driven for ventilation. Sometimes the words level, drift, adit, gallery, and rough, are used synonymously. In the greater part of England, and in most of the coal mines of France and Silesia, this motion is communicated by steam-engines. In the principal metallic mines of France, in almost the whole of Germany and Hungary, and in some parts of England and Wales, hydraulic machines perform the work. In other places machines moved by horses, oxen, and even human beings, are used.
If it be merely necessary to lift the waters to the level of the adit or gallery of efflux, advantage may be taken of the waters of the upper parts of the mine, or even of the waters turned in from the surface, to establish water-pressure machines, or overshot water-wheels, for pumping up the lower waters. This plan is successfully adopted in several mines in Hungary, Bohemia, Germany, Brittany, Derbyshire, and Cornwall.
There are many galleries or adits for drainage of several leagues in length, and sometimes they are so contrived as to discharge the waters of several mines,—as in the environs of Freiberg in Germany. The great drainage-gallery of the mine of Clausthal in the Harz is 11,377 yards, or 6½ miles long, and passes upwards of 300 yards below the church of Clausthal. Its excavation lasted from the year 1777 till 1800, and it cost about £66,000.
The greatest British work of this kind is what is called the Great Cornish Adit, which extends through the large mining district of Gwennap in Cornwall. It commences in the valley above Carnon, and receives the branch adits of fifty mines in the parish of Gwennap, forming excavations and ramifications which have an aggregate extent of between 30 and 40 miles, and which in some places are 400 feet below the surface of the ground. The longest branch is from Cardrew Mine, and is 5½ miles in length. This great adit drains a tract of about 5550 acres in area, and discharges nearly 1500 cubic feet of water per minute. Rather less than one-third of this stream is collected at the adit-level, whilst the remainder is pumped up from a mean depth of about 190 fathoms. The temperature varies between 60°-5 and 68°, and is on an average more than 12° above the mean of the climate. It opens into the sea at Strongest Creek, and empties its waters into Falmouth Harbour.
Under "Lead Mines" we shall notice the Nent Force Level in the north of England, which drains the numerous mines of Alston Moor.
The steam-engine, applied to pumping, has been the great helper of deep mining, whether in coal or metallic districts. Without it many first-class collieries could not have been won, and many metallic mines must have been long since abandoned. It is now almost a denizen of all lands; it exerts its mighty energies on the frowning cliffs near the Land's End, fumes in the narrow valleys, and it is planted on the high table-lands of Mexico. The first steam-engine in Cornwall was erected at Huel Vor, a tin mine in Breage, and was at work between 1710 and 1714. This was known as the old atmospheric engine, which continued in use long after Watt took out his patent; but the superiority of Watt's engine became so apparent, that it gradually advanced in fame and use. In 1778 the improved engines of Newcomen were giving place to Watt's engines. Watt required, as his remuneration, one-third of the saving of coal effected by his engines as compared with the old. To ascertain this saving a counter was invented, which, being attached to the main beam, marked the number of its vibrations, and thus the work done and the saving of coals effected were readily calculated. Cornwall being without natural fuel, coal is enhanced in cost by its freight from other parts; hence the Cornish engineers have been ever studious of extracting as much as possible of the heating power from coal. The result of their efforts is, they have extracted more heating power out of a bushel of coals than other engineers.
The saving of coals by three of Watt's engines at Chacewater mine exceeded £7200 per annum; and although the patent-right no longer exists, the same mode of calculating the work by counters is still in use, and what is termed the duty of an engine is estimated by the number of pounds weight (always expressed in millions) lifted one foot high by the consumption of one bushel of coals. In 1812 Captain Joel Lean suggested the plan of publishing the estimated duty of the Cornish engines, ascertained by a counter placed on every engine. This plan gave a great stimulus to improvement. The counter is furnished with a Bramah lock, the key of which is retained by the reporter, who, by monthly inspection of the engines, and the orders for quantities of coals consumed, ascertains the consumption of fuel and the duty performed. The "duty-papers" are then made public, and include not only pumping-engines but also drawing-engines, and those used for the stamps which pulverize the ores. The whole particulars being arranged, the duty of any engine may be found on inspection, and for any reported year. If, for example, we wish to find the duty of the celebrated Taylor's engine (cylinder, 85 inches diameter) at the Consolidated Mines, for the half-year ending June 1837, we inspect the returns, and see it registered as 63,020,000 lb. lifted one foot high by the consumption of one bushel of coals. The duty of Borlase's engine at Huel Vor Mine (cylinder 80 inches), was, for the same period, 74,073,000 lb. lifted one foot high.
Another example for the same time, was the duty of an engine of 70 inches cylinder at North Roskear Mine, namely, 79,335,000 lb.
It appears from a tabular view drawn up in 1838 that, since the establishment of duty-papers, the work performed by the ordinary engines has been more than doubled in twenty-four years, and the duty performed by the best engines during that period has been more than trebled. Taking the two extremes of that table, in 1813 the average duty of the best engine was 26,400,000 lb. lifted, while in 1837 it was 87,212,000 lb. lifted. This is a wonderful advance from the early supposed average duty of less than 17,000,000 lb. lifted. It must, however, be borne in mind that there is a wide difference between the common and the best engines.
The subjoined table presents the average duty of Cornish engines for four years:
| Years | Number reported | Average duty | |-------|-----------------|--------------| | 1839 | 74 | 48,880,000 | | 1840 | 58 | 49,730,000 | | 1841 | 51 | 50,920,000 | | 1842 | 45 | 51,620,000 |
The highest duty recorded is that of Taylor's engine, Large engine.
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1 Watt, writing to Boulton in 1783, gives some interesting particulars of Cornish mines at that time. He says—"Poldice has sunk a very great sum, and is not now gaining nor saving. It has cost L35,000 to fit up a drain, Wheel Virgin, in this working, and it costs above L10,000 a-year to drain the water, after all that can be done for them. Poor adventurers have sunk near L14,000, and have no great prospect of recovering any part of it. At Dolcoath, it is said, they have L6000 in borings already; and a new kibble-rope of above a ton weight is worn out in a fortnight. It takes full fifteen minutes to draw a kibble of ore there, which weighs only about 3 cwt. On the average, about two-thirds of the stuff drawn is barren stones. It cost three years' work, and I believe as many thousand pounds, to sink a new shaft in this mine. Every fathom of an engine-shaft that is sunk under the engine costs from L50 to L100. If we had not furnished more effectual means of drawing the water, I believe almost all the deep mines had been abandoned before now." (Letter from Watt, dated May 18, 1783, to Boulton.) Mines and Mining.
United Mines—being 110,000,000 lb. lifted. The average duty of the best engines has been, during a recent year, as high as 100,000,000 lb. lifted. The total force of steam-engines now at work is estimated as 5510 horse-power. The number of engines at work is reported as 82. The average duty in 1843 was 55,230,000 lb. lifted; in 1853 it was only 48,000,000 lb. lifted; refuse coal being largely used.
The annexed are the largest engines now in use in that district:
- United Mines and Consolidated, Polmadie. - Huel Prosper and Huel Darlington. - Godolphin, United Hills, Huel Tor. - Powey Consols, Duffield, and East Huel. - Croft.
The great 90-inch engine at the Consolidated Mines cost at the foundry L2000, and the pit-work cost L2000 more. The expense of putting it up was L4000; so that no less than L8000 was expended in its cost and completion with the pit-work. In twenty-four hours it consumed about 180 bushels of coals, delivered at one shilling per bushel. It lifted sixty-four gallons of water per stroke, and can work twelve strokes in a minute.
The great increase of duty above noted arises principally from three causes:—1. A reduction of pit-work resistances, if not balanced by an increase of water delivery. 2. A reduction of engine resistances, conjointly with an increase of power from a given quantity of steam, by using high-pressure steam (of forty or fifty lbs. to the square inch) expansively. 3. An increase of water evaporated in the boiler per bushel of coal consumed, by carefully preventing the radiation of the heat from the boiler, cylinder, &c.
The greatest quantity of water discharged from any of the Cornish mines in 1837 was from the Consolidated and United Mines in the months of February and March, when there were discharged from the Consolidated Mines 1657-18 imperial gallons of water, and from the United Mines 1634-49 imperial gallons, in each case every minute. Such was the estimate of parties connected with the mine, although it has been considered too high. Sir C. Lemon ascertained that the whole quantity of water pumped up by sixty Cornish engines in 1837, reached the enormous amount of nearly thirty-seven millions of tons. A single mine, Huel Abraham, yields the vast quantity of 43,500 hogsheads of water in twenty-four hours, pumped up from a depth of 1441 feet. In reply to inquiries, we are informed that the average quantity of water raised by Devonian and Cornish engines is about 9000 imperial gallons per minute.
The engines for draining are erected near to the shaft in which the pumps are fixed, which is called the engine-shaft. One end of the beam hangs over the centre of the shaft, and is attached to the pump-rod, which is raised at each stroke of the engine, afterwards sinking with its own weight, which is always counterbalanced by a balance-pan; so that the whole power of the engine is exerted in raising the column of water in the pumps. An engraving of the pumps used in metallic and coal-mining is to be found in Plate CLXXVI., illustrating the article Colliery, in this work.
A large and substantial building generally houses the engine, having galleries affording convenient access to every part of the machinery. The centre of the beam is supported by the front wall of this house, and a low building attached to it contains the boilers, which in Cornwall, together with the steam-pipe and cylinder, are carefully cased and covered up with some non-conducting substances.
A very large expenditure is necessary for the materials consumed, both in the engineering and mining departments of the Cornish and Devonian mines. Of this the expenditure for one year (1837) will be a sufficient example:
| Material | Quantity | Cost | |----------------|--------------|---------------| | Coals | 55,800 tons | L0 17 0 per ton | | Timber | 14,056 loads | 2 12 0 per load | | Gunpowder | 300 tons | 44 0 per ton | | Candles | 1,344,000 lbs| |
The roofs and sides of mining galleries must frequently be supported by timbering. In a gallery it may be sufficient to support the roof by means of joists placed across, and bearing at their two ends upon the rock; or the roof and two walls may be upheld by means of an upper joist resting on two lateral upright posts. From these simplest forms various adaptations, up to the most complex timberings, may be employed. An ingenious system of cross-bars is used in the Hartz for supporting the wall of a lode during excavation.
Considerable timbering is often necessary in shafts. Coal-mine shafts are often lined with timber in the north of England. Woodwork for shafts sometimes consists of rectangular framing, and sometimes of circular. In the Newcastle district coal-pit shafts are frequently tubbed to a considerable depth; and, when the feeders of water have been copious, iron tubbing is employed. Plank tubbing, when well executed, will sustain a pressure of 100 lbs. to the square inch, and endure for many years, when the water is fresh; but if salt, it corrodes the iron nails, spikes, &c. Solid wood tubbing, neither requiring planks nor spikes of iron, when solidly and smoothly fitted, is convenient, is very durable, and will often sustain a pressure of twenty atmospheres. But iron tubbing is now most frequently used in coal-mine shafts where copious water issues from sands. This, though costly, is very durable, and was applied in a colliery in Durham where all hopes of success seemed unfounded. It will sustain an enormous pressure.
The total quantity of timber in use for mining purposes in Cornwall would require no less than 140 square miles of forest of Norwegian pine, averaging a growth of 120 years. Taking a very speculative year (1836) as our example, the consumption of timber for mines was estimated at 36,200 loads, or 144,800 trees. The cost of timber imported in the same year was L176,000; the drawback in the duties of which amounted to nearly L82,000. The cost of timber for the Devon and Cornish mines in that year amounted to L94,138. In the year 1837 the loads were 14,056, and the cost L36,545.
The descent and ascent of most metallic mines in Cornwall is made by ladders, of about 25 feet long and with steps from 10 to 12 inches apart. Successive ladders are placed slopingly, and at the foot of one ladder is a platform named a solar, with an opening leading to the next ladder beneath, which is generally placed parallel with the one above. The fatigue of descending to great depths by successive ladders, and especially of returning after the day's work, and ascending these ladders, is very great. We may compute that one-third of a miner's whole physical strength is expended in going to, and more in returning from his work. In the year 1833 an accident suggested a new method to one of the Hartz miners, who availed himself of the reciprocating motion given to the pump-rods in the shaft. A portion of 100 fathoms was divided into 22 minor portions, and on each of these an iron step was fixed at intervals of four feet, while hand-holds were placed at convenient distances. A reciprocating motion of 4 feet being given to each rod, the miner stepped from one rod to the parallel one on the other when it arrived at his standing place. As one rod is always ascending while the other is descending, the miner can thereby ascend or descend at pleasure by stepping from one rod to the other. It is evident, for illustration, that if two rods A and B (fig. 5) be alternately descending and ascending by the communication of a reciprocating motion to them, then the steps... Mines and mining.
Mines and \(a, b, c,\) and \(d,\) fixed on \(A,\) will, in every motion of, say four feet, be even with the steps \(g, h, i, j,\) &c., fixed on \(B.\) If \(A\) descend and \(B\) ascend, then one movement will bring a level with \(g,\) and \(b\) with \(h,\) &c., so that a man beginning with \(a\) can step over to \(g\) when on the same level, and then he will be borne down, upon the next movement of \(B\) downwards, to \(b;\) from \(b\) in like manner to \(h;\) and so on successively until he arrives at the lowest step. In ascending he has only to reverse this action, and he will in due time reach the surface without fatigue.
In the Fowey Consols Mine a man-machine of this kind extends to a depth of 1680 feet. It is improved by stationary platforms, the rod carrying down 12 feet at a movement. Other improvements may be adopted; and these man-machines are remarkable economists of labour, life, strength, and money. To descend 1700 feet requires only twenty-five minutes.
This machine is one of the most signal alleviations of the miner's toil which has ever been invented or applied. It ought to be generally adopted, as there is no objection on the ground of expense. In Cornwall the loss of time weekly sustained by workmen in descending and ascending ladders is estimated at three shillings, and the loss by man-machines at ninepence. They are now in very general use in the mines of France, Belgium, and Germany; and it has been shown that the saving, even in money, by the use of these machines, is considerable. Thus, in a mine where 250 men descend and ascend a shaft of 150 fathoms, the cost per annum is comparatively as follows:
\[ \begin{array}{ccc} \text{Ascent and descent by ladders} & \ldots & \ldots \\ \text{by man-machines} & \ldots & \ldots \end{array} \]
An engineer has shown how 10,000 miners might, by adopting these machines, save no less than £39,000 per annum in the value of time alone. (For fuller details, see Cornwall: its Mines and Miners, &c., p. 155-161.)
It remains to explain the peculiar system by which mining labour is conducted in Cornwall. The two great classes of work-people consist of the surface men and the underground men,—the latter being about three to one as compared in number with the former, and being again divided into two strongly-defined classes, called provincially "tutwork men" or "tutmen," and "tributers." Tutmen are simply excavators, paid at a fixed rate per fathom. Their undertaking is to bring to the surface so much material, whether ore or mere "stuff," at the agreed price. Such men are necessarily the first labourers in a mine, as they sink the shafts and drive the levels. They form a party, or gang, consisting of several persons, and each party is divided into three gangs, each gang working eight hours at a time, the whole number thus taking their turns in the twenty-four hours. The price at which they are set to work is the only subject of dispute. The work is given out by the officers of the mine at a price per fathom, which the tutmen are to bid for. They bid with a real or supposed knowledge of the nature of the ground, and the party offering to take it at the lowest price secures the work. To fulfil their task they require the use of machinery to raise the excavated matter to the surface, and they are allowed to use the machinery on the ground at a certain rate of charge, to be deducted from their earnings. Other deductions are made for candles, powder, safety-fuze, smiths' costs, &c. In a case before us six tutmen took a contract for a month, and, after all deductions, each man earned L2. 16s.
The "tributers" do not work for fixed wages of so much per fathom, but become, by a peculiar arrangement, partners Mines and Mining, of the mine as regards the portions or "pitches" which they respectively undertake. We have already explained that the pitches are the rectangular portions into which the part of the mine containing the lode is divided, as shown also in the illustrations. The method of arranging the excavation of these is as follows:—A mine has its regular "setting day," on which the captain of the underground work meets the tributers at a fixed time and place. A mining auction now takes its course, the captain acting as auctioneer and partly as appraiser. Particular pitches are named and put up by the captain. The tributers who form the bidders have, it is presumed, studied the character and metallic prospects of each pitch, and their knowledge and skill is now brought into exercise and competition. They are now about to agree to get the ores in the pitch in question, to break them, to raise them to the surface, and pay for the whole process of dressing them (if so required) and bringing them into fit condition for the smelter. It is evidently the object of the captain to set each pitch at the lowest price, so that his aim is the reverse of that of an ordinary auctioneer; and as the captain represents the proprietors, his interest is to secure the extraction of the ore at the smallest payment. The tributer will bid in proportion to his idea of the richness or the poverty of the pitch put up; if rich in metal, his labour will of course be less than if poor, and his reward greater. Quality and quantity of metal will regulate his offer. For example, he may offer to work the pitch put up, if rich in ore, at five shillings in the pound, that is to say, five shillings deducted from every pound's worth of ore raised to the surface, such being his tribute; and hence the name of tributer. If the pitch seem poor in ore, he may not take it under thirteen shillings in the pound; and the prices offered vary from one to thirteen shillings in the pound. The whole setting is generally arranged without much difficulty or difference. The pitches are set in this manner for two months at a time.
When the tributer proceeds to work in the manner previously described, he discovers the value of his bargain. If he finds the pitch much poorer than he expected, two months will terminate his bad bargain, if much richer, two months will terminate the bad bargain of the captain. If the tributer find his pitch to turn out extremely poor, he may throw up his agreement at the end of one month, or previously by paying a fine of twenty shillings. The preference is given to men best known and longest established in the mine. There are great and mutual advantages in this plan of conducting the raising of ores; and although the tributers are often disposed to complain, yet it may be doubted if any other equally beneficial and equitable mode of carrying on the work could be devised.
To show the operation of this system, we shall give an example occurring in actual work. The ore are raised by a certain party of tributers sold for L182, 2s. 2d.; and as the tribute was 7s. 6d. in the pound, the share for the tributers was L68, 5s. 9d. From this sum the following deductions were made by the "adventurers" or owners of the mine:—For 108 lb. of candles, L3, 12s.; for 195 lb. of powder, L6, 10s.; for safety-fuze, L1, 9s.; for hills, 1s. 9d.; cans, 2s. 6d.; saws, 6s.; locks, 1s. 6d.; smith's work L3, 19s. 6d.; drawing, L3, 0s. 11d.; cost of dressing, L6, 10s. 8d.; use of grinder, 8s. 10d.; sampling and weighing, 17s. 6s.; "subsist," or money drawn on account, L36, 18s.; total, L63, 18s. 2d. Thus the actual costs amounted to about L27, or 40 per cent. on the tribute; and the men had drawn so largely beforehand that they had only to receive L4, 7s. 7d.
The earnings of tributers vary so greatly, from the nature of their work and from the system, that no average can be deduced. It was, however, found in 1837 at the Fowey Consols Copper Mine, that the average monthly wages of Mines and 340 tributers were L.3, 7s. 1d. each, while the monthly average of 358 tutmen was L.2, 19s. 2d. each.
The remainder of this article will treat of the position, produce, statistics, and mines of the more important and useful metals, under each metal separately. (For additional information respecting gold and silver, not strictly belonging to mines and mining, see the article Precious Metals.)
GOLD.
Gold is less the subject of mining, strictly so called, than almost any other metal, as it is chiefly distributed in auriferous detritus. Some considerable portion is found in combination with iron pyrites and other metals, as silver, tellurium, and mercury. From silver it is obtained by a process termed quartation. Dr Percy has detected minute quantities of gold in almost all lead ores, and is disposed to believe that gold may have been thrown down by deposition from an aqueous medium; while Humboldt suggests that the formation of gold has some closer relations to, or dependence upon, the atmosphere, than lead, copper, or iron.
Great mistakes have been made, and may be repeated, concerning gold in veinstones. For example, about twenty-seven years ago lumps and specimens of gold were brought from North Carolina to London to induce the formation of a gold-company. Fortunately a competent mining surveyor was sent out, who found numerous filaments and traces of gold in the pyrites and on the surfaces of the rocks, but he soon satisfied himself that "the veinstones had no body of ore downwards," and thus prevented a ruinous expenditure. Lodes or veins of copper, argentiferous lead, iron, &c., have been found in numerous instances to become more and more productive as they have been followed downwards; while, on the contrary, gold has invariably (hitherto) proved to be much attenuated in its descent, and in most instances to disappear at considerable depths. The auriferous quartz "reefs" in Australia run down sometimes from the surface between sandstone, slate, &c., but always seem to run out at a depth of generally less than 100 feet. This downward attenuation of gold veins in rocks is an opinion held decidedly by Sir R. I. Murchison (see the new edition of his Silurian System, the chapter on gold) and some other geologists. Reports from Mr Selwyn, government geologist, New South Wales, and from Mr J. S. Wilson (who has passed three years as a gold miner in the Sierra Nevada of California, and has communicated a memoir to the Geological Society of London), decisively confirm the above-stated opinions and facts concerning the downward impoverishment of quartz veins containing gold, and demonstrate that the richest produce is essentially derived from loose superficial debris piled up on mountain sides or slopes, or in ravines, and at various considerable altitudes above the sea.
It will be found upon examination, that in nearly all the gold countries the chief supply has been derived from the alluvial deposits, and but a small proportion from veins and rocks; and few deep mines have succeeded. Brazil indeed presents some examples of successful subterraneous gold mines; and in two establishments at the famous Minas Geraes the veinstones have proved highly remunerative, though the ore is seldom long continuous; but the loose rubbish of Brazil has afforded its chief supplies of the precious metal. Nearly all the gold in Chile is procured from sands, detritus, conglomerates, and loose debris. In Peru and Bolivia the ancient drift or diluvium has afforded most gold; and in Columbia the great mass of gold has for many years been derived from diggings and washings in similar deposits. The celebrated mines of Beresov in the Urals have, however, shafts 105 feet deep, and galleries in which the gold lies in soft decomposing gneiss, studded with bright veins of quartz and quantities of silvery talc. Brown spots of crumbling iron pyrites are strewed through it; but the large crystals of brown ironstone are only met with where the quartz is deposited in narrow and tortuous streaks and veins. It is from both sides of the hard white lines that the entire iron ore is collected containing the gold, partly dispersed in fine plates, and partly accumulated in lines and filaments like wire. The ore is followed in every direction.
With reference to the precise locality of the most ancient sources of sources, termed Ophir (Supara of Ptolemy), nothing definite is known. The people living near the sources of the Indus obtained, according to Herodotus, a large quantity of gold from the eastern border of the Great Bactrians, and the desert steppes of Cobi. Much was obtained by washing sands, and more by digging. Herodotus again tells us that "in the north there is a prodigious quantity of gold; but how it is produced I am not able to tell you certainly." Pallas, in his Travels, describes the remains of these mines. Mines were also visited by Lepeshkin and Gmelin on the southeastern borders of the Ural Mountains, which were in all probability the work of a nomadic people like the Scythians. This gold region still continues to yield treasures to industry. The extent of the works shows that the ancient workmen must have been very numerous; whilst an inspection proves that only the first rudiments of the science of mining could have been known. With very imperfect instruments (some of which remain) they must have worked very long and very patiently. They seem to have scraped out the gold with fangs of the boars, and collected it in leather bags or pockets. Some of the pits are 20 fathoms deep, shaped like a bell, and are about 7 feet in diameter. The passages and props are well excavated and arranged, but the former are extremely low. The natural pillars left to support the roofs are still effectual for that purpose in some parts, and in these are still found small portions of copper ore containing particles of gold. Human bones, probably of the workers, are found in the ruins of other pillars. Only the richest ores were worked, and some of them must have been smelted in the mines, for in the rubbish melted copper and smelting implements have been found. The operations of crushing and washing the ores were performed in the rivulets; and the smelting, whether in the mines or at the surface, was performed in small furnaces, of which Gmelin observed nearly a thousand in the eastern parts of Siberia. These were made of red bricks, and in them pieces of melted copper two and three pounds in weight have been found.
From the mines of Nubia and Ethiopia it is evident that much gold was produced. These mines, like those of the Uralian chain, produced a copper yielding gold, which the Africans knew how to separate. Belzoni discovered that a very extensive tract had been worked in the Sahara Mountains. The Pharaohs derived their wealth from these sources at the expense of much human suffering and loss of life. Mr Jacob concludes, from a close examination of the subject, that not less than L6,000,000 sterling of the precious metals must have been annually produced from these mines, and that a large proportion of this must have been gold. This source of gold may have become very productive.
There were gold mines in Thrace and in the island of Thasus. Thessaly produced ores which were rich in gold, and Epirus rich silver ores, and there were rich silver mines in Attica; and from all these sources the Athenians drew their wealth. (See Boeckh's "Dissertation on the Silver Mines of Laurion," in his Public Economy of Athens.) They extended from coast to coast, in a line of about 7 English miles, from Anaphlystus to Thoricus. The ores extracted contained silver and lead, with zinc, and probably copper, but no available gold. These mines were worked by means of shafts and adits, and whole masses were removed, so that the supports alone were left standing. The state was the sole Mines and proprietor of them, but they were never worked at the public expense. They were always granted to private individuals in fee-farm, and these leases were transferred from one person to another by inheritance, sale, and other kinds of legal conveyance. When Themistocles proposed to the Athenians to apply the funds obtained from the mines to the building of ships, instead of dividing them as before amongst the people, the annual receipts appear to have amounted to 30 or 40 talents.
The Romans, who monopolized as much of the mining produce of the world as they could, found the principal sources in Upper Italy, in the province of Aosta, in the Noric Alps, and in Illyria. From this district gold was abundantly obtained at one period, partly in large grains on the surface, and partly in mines, so pure that an eighth part only was lost in the process of smelting and refining. Its great quantity caused a decrease of one-third in the price through all Italy, and induced the proprietors to employ fewer workmen in order to raise the value. The people named the Tarbelli, at the foot of the Pyrenees, also worked the soil extensively for gold. Amongst the most productive mines in particular belonging to the Roman republic, we may name the rich gold mines near Aquileia, those of Ictiumuli near Vercelli, in which 25,000 men were constantly employed (Pliny, Hist. Nat., xxxiii. 4), and the silver mines in Spain, in the neighbourhood of Carthago Nova, which yielded every day 25,000 drachmas to the Roman Exarum (Polyb. xxxiv. 9). We are informed by Pliny that the Emperor Vespasian obtained annually from Galicia, Asturias, and Lusitania, L60,000 of gold; while the silver was found in such quantities in Spain, that Hannibal extracted from a mine worked by him near Cartagena daily a produce exceeding L300 of gold. Cato delivered into the treasury 25,000 lb. of silver in bars (L120,000 in our money), besides 400 lb. of gold, all of which he had accumulated in Spain. Helvetius, who was only governor of Andalusia, delivered 37,000 lb. of silver in coin, and 40,000 lb. of silver in bars. Strabo also informs us that neither gold, silver, copper, nor iron, were found in such quantities and excellence in any part of the known world as in Tartessia (Strabo, Geograph., p. 194). The Hungarian gold mines do not appear to have been worked before the eighth century, and the mines of Sweden and Norway not until a later period. In our own country, to the conquest of which the Romans were incited by the reported wealth of the inhabitants in gold and other metals, we do not find many evidences of ancient mines of the precious metals. Cimboline, prince of the Trinobantes (which included Essex), is stated to have coined gold money instead of rings. It is curious that Henry IV., by his letters-mandamus, commands Walter Fitz-Walter, upon information of a concealed mine in Essex, to apprehend all such persons as he in his judgment thinks fit, that do conceal the said mine, and to bring them before the king and his council, there to receive what shall be thought fit to be ordered.
The Welsh Triads celebrate princes as being possessors of golden cars, and in all probability this induced the Romans to penetrate into the principality. It has been recently found that the Romans worked the Gogofan or Ogafau Mine for gold, which is near Pamsant in Caermarthenshire. A Roman station is indicated by the remains of pottery and ornaments found on the spot; and several gold ornaments, and a very beautifully-wrought gold necklace, probably manufactured in the locality, have been discovered.
It is very remarkable, as has been observed by Sir R. I. Murchison, that the countries which were successively to give laws and civilization to the ancient world—viz., Lower Egypt, Greece proper, Italy, &c.—should all alike have been destitute of procurable gold from their own soils, arising from the geological cause that those countries contain no mineralized old rocks. It were a curious geological problem to ascertain why the older strata, when mineralized, are pre-eminently auriferous, and the secondary and tertiary strata, when altered and mineralized, are not so. Italy, south of the Po, contains scarcely any stratum older than secondary limestone, and is totally destitute of gold, a part of Calabria being the only exception. In proceeding, however, to Sardinia and Corsica, where silurian and crystalline rocks are found, there we observe that gold mines have been worked in the oldest ages.
Adolph Erman, in his Reise um die Erde, and Geographische Verbreitung des Goldes, Berlin, 1848, gives some valuable information on the geographical distribution of gold, and has appended a gold map of the world to the latter of the above-named works, in which he marks seventy-seven tracts in which gold has been worked, or is known still to exist, and shows, in contradiction to the old-received opinion, how greatly it predominates in the northern hemisphere.
With reference to its geological position, gold is found in the primary group of rocks, including the transition strata of earlier writers, which, as they contain the oldest organic remains, have been technically denominated palaeozoic. This series constitutes the dorsal spine of the great mountain chains of both the old and the new world. There are, however, vast regions, amounting perhaps to three-fourths of all known lands, where no such rocks appear. Experience has shown that it is only in the primary group of rocks, as above defined (including certain associated igneous rocks), that gold has been found in quantities sufficient to pay for working. All the veinstones or rock masses from which much gold has been derived, whether by natural catastrophes or by human endeavour, belong to the primary and transition group (or what are now called the azoic and palaeozoic rocks), and especially to those portions which have been modified by the eruption of matter in a state of fusion, or at a very elevated temperature. It is thought that the gold-producing rocks are not confined to particular geographical zones, as formerly supposed, but they are found protruding more or less in meridional bands in all countries where the primary series is visible.
In the Ural district, at Ekaterinburg, and north and south of it, gold was discovered in the beginning of the present Urals century, and being traced to its parent source, small underground mining drifts were sunk on the quartz veins in the schistose and granitic rocks, which gave a scanty revenue. Gold was, however, subsequently discovered in lumps, grains, and scales in the gravel and sand on the sides of the brooks in the same district; and trials soon convinced the miners that it was far more profitable to wash the gravel and shingle, than to follow laboriously the quartzose veins containing threads of gold in the solid rock. The result has been the establishment of diggings and washings at different points between Petropanloisk in the north and tracts south of Minsk, which have afforded for many years yields of gold worth from L500,000 to L700,000. All these localities of auriferous gravel, shingle, and sand, are in the vicinity of those spots where Silurian and Devonian sandstones and schists have been penetrated and altered by the eruptive rocks before named. The gold, when traced to its original matrix, is found to occur chiefly in veins of quartz in the form of lumps, threads, and flakes. These veins rise, geologically speaking, from beneath; for they are seen to cut through all the strata or beds of which the hills were originally composed.
In considering the original derivation and formation of auriferous, alluvial, or diluvial deposits, the following theory appears most applicable:—When the primordial breakers, waves, and currents acted on the rocks containing gold, whether it were disseminated through the mass of the rock, or confined to the quartz veins traversing it, fragments of the auriferous rock would be detached equally with other pieces. Such fragments, either slightly water-worn or alto- Mines and Mining.
Minerals broken and ground down, would afterwards be found in the drift clays, sands, and gravels, and would, in all probability, be much richer in gold than the actual gold-bearing rocks themselves. A current of water having sufficient force to bear along sand or pebbles of quartz, or any other rock of perhaps 2½ specific gravity, might not be able to move associated fragments of gold, which metal has a specific gravity of 18 or 19. Moving water, therefore, has formerly effected upon the auriferous rocks that which the miner would now effect, namely, broken them up into fragments, swept away the lighter particles, and left the gold behind.
Rivers are great natural cradles, sweeping off all the lighter and finer particles at once, the heavier ones either remaining against any natural impediments, or being left where the current slackened in force or velocity. There are reasons why the auriferous drift may be richer in gold than the mass of the rock from which it is derived; and there are other reasons also why the auriferous drift of a country first deposited after the first formation of the gold, should be richer than any subsequent one.
The Gold districts of Australia have created the greatest excitement, and given rise to extravagant anticipations, as well as to much personal disappointment in the failure of foolish expectations. In the numerous publications of visitors to these regions, we find but little scientific information, nor are we yet able to form precise ideas as to all the geological conditions of these repositories.
At present the search for gold, at least in Australia, is chiefly confined to the alluvial beds. Of these, we learn from one geological visitor that at the Ballarat diggings, in the gold-fields of Victoria, the alluvial deposits may be thus divided:
I. Older than Basalt. A. Before the eruption of basalt and the bearing beds (charriages) of basalt boulders. B. Contemporaneous with charriage of basalt boulders.
II. Newer than Basalt. C. Newer beds covering the basalt boulders, but older than the formation of the existing valley.
The source of the gold appears to be an indefinite succession of clay-slate, and of argillaceous-arenaceous-micaaceous slates, seemingly interstratified, as regards their strike, with quartz veins of all sizes, which form the matrix of the gold. The basalt hems in the gold district on the east and west as an iron framework.
A report of a select committee of the Victorian Legislative Council has just been published, in which a very favourable estimate of the richness of the Victorian gold-field is given. Mr Brache, said to be a reliable authority, estimates the auriferous lands of the colony to be 20,000 square miles, including 20,000 square miles of quartz reefs. He computes that there are about 20,650,000,000 tons of quartz, which would take 100,000 miners about 300 years to work up. The alluvial lands are further estimated at 20,444,000,000 cubic yards, and if worked up by 100,000 miners at the rate of 90,000,000 cubic yards per annum, they would occupy 2240 years. The grand total of the auriferous wealth of that colony is estimated at L26,783,000,000 sterling. The aggregate receipts for the five years from both districts amounted to L41,830,696, of which L7,032,141 came from New South Wales and L34,830,696 from Victoria. It appears that all of this vast amount, except about two millions, was brought direct to this country. The Australian produce of gold for 1856 has been estimated at 120 tons in weight and L13,000,000 in value.
Mr Wyld says, that the whole range of the Australian Alps, 200 miles long, is supposed to afford sites for gold-diggings. Sooner or later the working of alluvial gold soils will cease to be highly gainful. The question will then be decided whether quartz-crushing for gold can be sufficiently remunerative. Many companies for this object have been projected, and nearly all have failed. There are many, however, who still think highly of quartz-crushing. A geological problem also still to be decided is the continuance of the veins or strings of gold beyond a moderate depth.
Respecting the ultimate production of Californian gold, it has been thought that the metal is too richly sprinkled to promise any very long continuance of an abundant yield; for it is almost a law among miners, that ore too highly condensed in any given locality of lodes or veins is, in the long run, much less profitable than when broadly and widely diffused throughout a mass of rock. Hence other regions whose gold is disseminated through mountain masses may afford a supply for ages to come, long after the rich gravel troughs of California shall have been exhausted. Much, however, may possibly be derived from Upper California. There is a remarkable geographical feature connected with the mineral phenomena of California noticed by Murchison. All the great quantities of gold have been derived from some twelve or fourteen localities in that portion of the western flank of the Sierra Nevada which assumes a north-westerly direction from that parallel to the meridian it had before followed between 37° 30' and 30° N. Lat. By reference to the map of Fremont, it will be seen that the centre of this westward deflection is directly opposite to where the extremity of an east and west ridge, which traverses the great saliferous basin, impinges on the Sierra Nevada, and is associated with the protuberance which alone has proved to be so eminently auriferous in all the long chain of mountains ranging from the eternal snows of Russian America to Mexico, Peru, and Chile. It is possible that the intersection of ridges may account for a great local development of metal, just as in mining practice at home and abroad it is found that the richest branches are often detected where lodes traverse each other.
From an American state paper just published, we extract United the following interesting particulars.—The gold and silver States. coinage of the United States, from 1793 to 1856, amounted to 549,341,514 dollars. In 1844, before the gold mines of California were discovered, the total of gold and silver in the United States was estimated at 100,000,000 dollars. The imports and receipts of bullion at the mint from American mines, after deducting the exports up to the 30th of September 1856, have added at least 150,000,000 dollars to the amount of gold and silver in the country, without taking into consideration the amount brought in by emigrants and returning travellers, or the amount carried out by travellers and merchants, not entered at custom-house, or the amount used in the manufactures or employed in the arts. In the fiscal year 1856-7 our country received from America imports of gold to the value of 33,000,000 dollars.
The gold region, so called, of the United States is a metalliferous belt extending in a south-west direction through the states of Virginia, North and South Carolina, and Georgia. Its length is about 600 miles, and it has a mean breadth from its southern to its northern edge, of about 80 miles. In every part of this extensive line native gold is met with in alluvial deposits, and in various streams where the contiguous rocky strata abound in quartzose veins more or less auriferous. In Georgia the richest mineral belt is in the talcose slate and granite formations, alternating with hornblende-slate, gneiss, and chlorite-slate. Parallel belts are found also near Augusta, but they cease with the termination of the primitive region. The most productive researches have been made in the branch streams or stream mines, and in the beds of rivers, rivulets, and ravines. A moderate amount of gold has been derived from the metamorphic rocks of the Lower Silurian range in Lower Canada; and very recently intelligence has arrived of larger auriferous deposits in Canada. The greatest increase of precious metals, except from Australia and California, has been from the mines of Russia. Sir R.I. Murchison considered the present production of gold from Russia to be nearly equal to L3,000,000 sterling per annum. The quantity of gold raised in that country during the five years succeeding 1847 was equal to about 296,932 lb. troy.
While our islands contain nearly every geological deposit from the oldest to the latest,—the older occupying all our mountainous tracts of the west,—it is only in some six or seven localities that gold has ever been largely found. British gold was not probably very abundant at any period, although the Druids may have found enough in the superficial gravel of certain limited tracts to serve for the manufacture of their beautiful "torques," armlets, and other ornaments. There may have been surface accumulations in Britain and Ireland (as in Bohemia, &c.), now totally exhausted. Some little gold, associated with the tin in the old and crystalline rocks of Cornwall and Devon, had long attracted the ancients; and so late as the reign of Edward III., we are told that the mines of North Devon furnished enough specie (possibly silver) to enable that warlike prince to embark in one of his campaigns; and even at this day pieces of gold, some as large as a pigeon's egg, are occasionally found at Combe Martin. In Cornwall a very small portion of gold is associated with the alluvial tin. In South Wales the Romans opened lofty galleries in the Silurian rocks for the extraction of small quantities of gold mixed with the pyrites. No British locality has afforded so much gold as the lead hills of Dumfriesshire, where, in the reign of James V., 300 miners were very profitably employed, and earned 4d. per diem,—in those days considerable wages. When the gold became scarcer the wages fell to 2d., and the works failed, like those of Bohemia and other exhausted tracts. It is said that some L20,000 have been expended in this locality to obtain L5,000 worth of gold.
In the Wicklow Mountains in Ireland there are rocks which might be expected to be auriferous. Two or three golden streams descend from the granitic mountain Croghan Kinsheela, and traverse the quartz veins in slate, and from these all the fragments of the precious metal have been derived, and minute portions are still sometimes found by the peasants. Formerly the government carried on the gold works, but the gains were infinitely exceeded by the expenditure.
In North Wales that part of Merionethshire which contains auriferous rocks lies between Dolgelly and the Moelwyn and Manod range, north of Festiniog. The gold at Cwm Eisen was discovered in 1843, and that mine alone has been worked, although bold assertions were made as to the gold to be obtained in that district. It has never been worked with a steady profit, as far as we can learn. The gold is found in a branching lode containing lead. Its principal branch runs north-easterly, and is mostly composed of exceedingly hard quartz. The neighbouring rocks are much disturbed and altered, and numerous little bosses of greenstone are intruded among its beds. At Dol-y-frwyngol gold has been found in unusual quantities, and the lode there is the most promising. It runs W.N.W. and E.S.E., in low ground, and is principally composed of a white saccharoid quartz irregularly traversed by numerous loose joints. It was first opened for copper, but gold was found in several flakes and grains irregularly disseminated through the quartz,—sometimes visible to the naked eye. Discoveries of gold have been made in the hills north of the Dolgelly and Barmouth Road.
We have instituted some particular inquiries on the present state of the Welsh gold speculations, and learn that the Dol-y-frwyngol Mine, 6 miles from Dolgelly, is the principal, or has been such, it having stopped. At this spot the adventurers had erected a steam-engine of, we believe, 70 horse-power, with grinding-pans about 10 feet in diameter, and four balls to rotate in the pans of 3 feet in diameter, together with a number of amalgamators, furnaces, &c. To all these was added an expensive staff. What was the result of mining? At a depth of 9 fathoms they "cut" or met with the quartz lode. At 20 fathoms they found gold-bearing quartz, and this continued to a depth of from 30 to 40 fathoms. Then they drove east and west, and found that the gold greatly diminished and nearly disappeared. Now the mine has stopped, and the adventurers have little hope of further success. In fact, the presumption we have expressed is in this case again confirmed, viz., that gold veins in quartz diminish in richness in proportion to their depth from the surface. The result of the crushing of the quartz in the upper parts is interesting. On the 16th August 1854 they crushed 39 tons of auriferous quartz, and found gold at the rate of 5 ounces 9 pennyweights per ton of quartz. Afterwards they crushed 100 tons, and found gold at the rate of 5 ounces per ton; then successively gold at the rates of 8 ounces 9 pennyweights per ton, and 4 ounces 15 pennyweights per ton. These ratios might have paid well if continued, but the expenses for extracting small amounts per ton are vastly more than the profits. We have examined some of the rich specimens, and found the gold visibly disseminated through the mass of quartz.
The processes by which gold is made ready for the metal-Preparlargist may be divided into three:—(1.) Washing; (2.) Trituration; (3.) Separation of the useful from the waste.
(1.) The washing is necessary to clear off the mud and dirt from the larger fragments, and to set free small particles of the precious mineral which are enveloped in clay. Various machines may be used to facilitate the operations, such as inclined cylindrical sieves, adopted in some of the Russian gold-washings, or annular sieves, or a conical sorting-drum.
(2.) Trituration is not so needful in gold as in other metals, for here nature has already been the great triturator. It may be necessary, however, in the case of auriferous quartz, to break down the masses either by hammers (buckers) or by crushers or grinders,—machines almost peculiar to this country, and to be seen in simpler forms at the lead mines in Cornwall and Wales, and in their more complicated forms in the northern lead mines. In instances where the portion of gold is very minute, stamps must be employed, in the form of a range of massive beams shod with heads of iron, and weighing each from 3 to 8 cwt.
(3.) Separation is effected by some of the very numerous contrivances which have been invented to facilitate the fall of the gold to the bottom when the whole mass is suspended in water; or, in another form, to cause the flow
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1 Those who are curious in the history of abortive gold-mining projects will find something to reward them in The Discoveries and Histories of the Gold Mines in Scotland, by Stephen Atkinson: written in the year 1619, and printed for the Bannatyne Club, 1825. From this book one might infer that gold was a staple product of Scotland—that it had been extracted in great abundance—and that from time to time it afforded employment to a considerable mining population. Atkinson mentions Crawford Moor and Friar Moor in Lanarkshire, and Wanlock Moor in Dumfriesshire, also of a small vein called Glengaber in Peeblesshire, as the chief auriferous districts. To this day, we believe, the shepherds occasionally find grains of gold in the channels of the streams which water these districts. In 1803 Professor Traill found specimens of gold in a vein of quartz near Wanlockhead mines, one of which he deposited in the museum of the Edinburgh University. King James VI. expended about L3,000 sterling (a large sum in his day) in searching for gold on Carnwath Moor, but he never obtained more than about three ounces, worth not quite L12. At the conclusion of this unprofitable speculation, Atkinson strongly urged the king to renew the national hunt for the precious metal, promising thereby "to make his majesty the richest monarch in Europe; yes, in all the world." Silver occurs in many natural forms and combinations, which are enumerated in the works of mineralogists. Native silver is found crystallized in wedge-form octahedrons, in cubes, &c.; at other times in dendritic shapes, or in arborescences, resulting from minute crystals being implanted upon each other. Fine specimens may be seen in the British Museum. Thirty-four specimens of silver from Sweden were displayed in the Great Exhibition. It most commonly occurs in small grains, without determinable form, or in irregular masses of various sizes. It is soft in its native state, but harder than gold, and its specific gravity is about 10. The ancients were acquainted with silver from the earliest periods; and it is constantly mentioned in Homer, though in a manner indicative of its comparative scarcity. It was much more abundant in Asia than in Greece proper. The Greeks worked the rich mines of their own country and its islands, the chief being in Siphnos, Thessaly, and Attica.
The native metal is found more or less in almost all the true silver mines now worked. Very fine specimens of native silver have come from the mines of Kongsberg in Norway, and some of these, beautifully crystallized, were displayed in our Great Exhibition of 1851. One mass discovered in 1834 at these mines weighed no less than 840 lb., as reported. In the Great Exhibition appeared a mass of native silver from Chile weighing 154 lb. It was found in 1850 at a depth of 200 feet. Its dimensions and weight are not its only interesting characteristics, for it is formed of successive layers folded on each other, like some beds of the coal measures, or like piled cloth when seen in cloth mills or warehouses. A large specimen of gold and silver in one mass lies under a table in the Museum of Practical Geology in London. It weighs 300 lb., and was brought up from the mine of Madre de Dios, from a depth of 45 yards, on the back of a miner. It contains 12 ounces of gold per ton of ore, and 220 ounces of silver per ton of ore. At Kongsberg the native silver occurs in carbonate and fluate of lime; at Schlangenberg in Siberia in sulphate of barytes; at Allenton in a ferruginous clay.
In our own country some few Cornish mines have produced silver in small quantities of extraordinary richness. There native silver has only been found in clay-slate; and the richest silver mines were Herland and Huel Basset. The former yielded about L8000 worth of ore, and the latter about L3000. It has been said that about L40,000 worth of silver came from a mine at Alva. Some specimens, in very small quantities, from Illogan parish, would yield at the rate of 2000 ounces per ton. The principal portion, however, of our silver is obtained from the "gosans" (ochreous iron ore) and the argentiferous leads.
The proportion of silver in the lead varies in different mines. In Cornwall it is supposed to be 35 ounces of silver to the ton of argentiferous lead. In Devonshire (the highest of all) it is supposed that 40 ounces can be extracted from the ton of lead in favourable instances; in Cardiganshire, &c., the proportion of silver is presumed to be 15 ounces; in the Isle of Man 20 ounces; in Durham, Westmoreland, and Northumberland, 12 ounces. In the year 1851 the total number of ounces of silver obtained from British lead was 674,458; and its value, at 5s. per ounce, was L168,614. In 1852 the total quantity of British (including Irish) silver from lead was about 818,325 ounces, valued at L205,080. In 1853 the estimated total quantity was 700,000 ounces, and the value L192,500. In 1854 the estimated total yield of silver from British lead was 562,659 ounces. The Beer Alston Mines in Devonshire are the most remarkable for their richness, and two lodes have produced large quantities of argentiferous galena, often containing from 80 to 120 ounces of silver per ton of lead.
Silver is now separated from lead by Pattinson's process, which is one of the most important of recent metallurgical improvements. From more than 30,000 tons of the lead raised the silver is extracted by Pattinson's process, which would otherwise have been lost to the arts. Thus (at the rate of 5 to 8 ounces to the ton) not less than L200,000 of silver are obtained annually. The result of this application has therefore been the actual saving of from L60,000 to L70,000 per annum to the country.
This dealverizing process is now employed in nearly all the lead-mining districts of Great Britain, and by its adoption the produce of silver has been increased to the amounts we have named, and nearly doubled within the last twenty years. Large quantities of lead, too, are annually brought to England for the purpose of being thus dealverized; and, in fact, it may be everywhere applied to alloys too poor in silver to be treated by capellation, it being both simple and economical; nor does it occasion more than 2 per cent. of loss of lead. This process has within the last few years been very generally introduced into the provinces of Murcia and Almeria in Spain; and a large quantity of silver, not formerly extracted, is thus obtained from the slightly argentiferous lead ores of the Sierra de Gador and of Cartagena. The cost of refining lead previously to Pattinson's process was from 30s. to 60s. per ton.
The total yield of silver annually from Europe and Produce. Asiatic Russia has been rated by Humboldt at 292,000 marcs, by others at 310,000; while at the beginning of the present century that of the Spanish colonies in America was 3,349,160 marcs, or nearly 12 times as much. The sum total is 3,704,160 marcs, which is nearly 1,900,000 lb. avoidupois, i.e., little less than 9000 tons.
We have already spoken of the richness of Spain in silver, Spain, and its yield in ancient times. It is only within the last thirty years that Spain has again become a silver-producing country, several very rich mines of this metal having been discovered since the revival of mining in 1825. The celebrated mines of the Sierra Almagrera, in the province of Almeria, were discovered in 1839, and they have ever since poured a large amount of silver annually into circulation. In 1843 the mines of Hiendelencina, in the province of Guadalaxara, were discovered, and these have been very productive. The produce of the Almagrera mines in 1850 was 40,596 marcs of silver, and it has probably since then remained about the same; but this amount is a decline from the earlier productions, the lode having become poorer, and water having hindered full operations. The veins of these mines run nearly north and south, and traverse finely-grained clay-slates and micaceous slates. The great lode of the Jaroso Mine is of extraordinary size, being in some places 6 or 8 yards, and even more, in width. The ores are chiefly argentiferous galena, the chloride of silver occurring but rarely in a separate state. The lodes of Hiendelencina run nearly east and west, and seldom exceed 3 feet in width; and are properly silver lodes, as they produce the ores of silver in chlorides and sulphurets, but unmixed with any ores of lead.
Europeans have undertaken the working of deep, extensive, and abandoned Mexican mines, with a confidence of their own superiority in the art and means of working such mines. The four essential points in mining are capital, Mines and industry, economy, and skill. These were thought to be at the command of the English; but in practice several drawbacks and obstacles—as distance, suspected frauds, &c.—have overcome the English. The single advantage of the introduction of the steam-engine by the English, burdened by almost insuperable difficulties in conveying it to the spot, and the deficiency of proper fuel when there, is not sufficient to counterbalance the numerous disadvantages under which they labour. Hence the history of English mining adventure in Mexico has been a history of failures and disasters, with occasional partial successes.
The mines of New Spain, the central group of which comprise three mining districts, including an area of about 1700 square leagues, are probably the most abundantly supplied with the precious metals of any in the world. Of the three districts the most southern of the group, that of Guanaxuato, is as remarkable for gigantic human labours in the mountains as for its vast natural wealth. A group of porphyritic hills, partly arid and partly covered with the evergreen oak, and the strawberry tree, rises on the ridge of one of the mountains of the Cordilleras, from a part of the great central table-land of Mexico. The absolute heights of the summits of these mountains range from 9000 to 9500 feet above the sea-level; but as the neighbouring plain is nearly 6000 feet above the sea-level, they appear only as insignificant hills to the traveller accustomed to the lofty mountains of the Southern Continent. The celebrated vein of Guanaxuato, the Veta Madre, crosses the southern slope of this porphyritic range, and the outcrop of the vein runs from S.E. to N.W. The quantity of the precious metals annually obtained from this vein, on the average of a number of years, amounts to two hundred and eighty-six thousand pounds troy weight of silver, being nearly double the average of the more celebrated mines of Potosi. The mountain of Potosi, however, has furnished, since its discovery in 1545 to the beginning of the present century, at least as much silver as was worth 235 millions of pounds sterling; although at the present day the quantity extracted is comparatively small, and the proportion of metal only about 1 in 2500.
The vein called the Veta Madre of Guanaxuato has been worked for a length of upwards of 6 miles, although the silver has been extracted only on a line of about 1½ mile. Its direction is (says Humboldt) N. 52° W., and its inclination from the vertical 45°, or 48° to the S.W. As this great mass of ore seems to have the same direction and dip as the clay-slate, it has been doubted whether it could be properly called a vein; but it appears to be a true vein, and divides into branches varying very considerably and capriciously in thickness. There seems to be a certain moderate depth at which the greatest riches occur, and this Humboldt states to be between 6000 and 7000 feet above the sea-level.
At the commencement of the present century the mechanical contrivances employed to work these mines generally were extremely rude. The whole of the ore was conveyed to the surface by human labour, the native Indians carrying a weight of from 240 lb. to 380 lb., exposed to a temperature of from 70° to 80° Fahr., for a space of six hours, and during this time ascending and descending several thousand steps in pits having an inclination of 45°.
The weight of the pure silver afforded by the Mexican mines in 1846 was about 1,047,582 lb. troy, and the value L3,457,020. The weight of silver yielded in 1850 was 1,631,313 lb. troy, and the value was L5,383,333. The weight of the produce in 1854 was 1,750,000 lb. troy. By reference to the table of general metallic produce at the end of the present article, it will be seen how far above other silver districts Mexico still rises.
The silver mines of the Andes are frequently in ground so high that the profits are diminished by the difficulties and cost of carriage, and the expenses of living and labouring in a barren country, destitute of water and sufficient fuel, and exposed to severe cold and snow. At the silver mines of Copiapo in Chile not a drop of water is to be found in a circuit of 9 miles. These mines are said to extend (as to capability) over 150 square leagues. The celebrated mines of Potosi in Bolivia were discovered in 1545, and since their discovery upwards of 1300 millions of dollars have been coined from them. Their total produce in pounds sterling is estimated at the astonishing sum of L250,000,000. They are situated in an insulated mountain about 18 miles in circumference, which rises to an immense height in the shape of a cone. Spaniards assert that there are 500 mines in Potosi; but these are only lots (estacas) portioned out to individuals, of which in 1826 there were not quite 100 at work. Cerro de Pasco in Peru is famous for its neighbouring rich silver mines. It is situated in 10° 48' S. Lat., at the height of 13,673 feet above the level of the sea. The mines have yielded, before the revolution, 130,000 lb. troy of silver. They have been suspended in consequence of the revolution. The water, which always occurred at the depth of 400 feet, took full possession of the mines. The house of Abadia, by which they were chiefly carried on, has been ruined. The table of metallic produce given at the end shows the yield of silver for 1854 from Chile, Bolivia, and Peru.
The mode of working many of the Mexican and Peruvian mines is primitive and perilous,—the object being to extract as much ore as possible without consideration of the future. Thus, in the rich Cerro de Pasco many of the mines are worked in a careless and disorderly manner. The dangerous parts in the shafts are never walled up, and the excavations proceed without precautions for security. Hence accidents are of frequent occurrence, and every year many of the Indians lose their lives. In the now ruined mine of Matagente (a word meaning "kill people") 300 labourers were destroyed by the falling in of a shaft. Rotten blocks of wood and loose stones commonly serve for steps, and where these cannot be placed, the shaft, which generally runs nearly perpendicular, is descended by the help of rusty chains and ropes, whilst loose fragments of rubbish continually fall in from the mouldering walls.
A recent report from Colonel Lloyd, chargé d'affaires in Bolivia, communicated to the Geographical Society of London, shows to what an enormous extent silver may yet be extracted from Copiapo, and from other South American mines; and as veins of silver and argentiferous lead frequently expand largely in their downward course, immense amounts of ore may be extracted. It seems to be the opinion of Humboldt and some eminent men, that the produce of silver will largely increase in the future.
Notwithstanding the very large quantities of the precious metals obtained from the mining districts of South America, the ores are not, on the average, richer than those of Freiberg, of Hungary, or of Transylvania. It is not, therefore, as has been generally supposed, from the intrinsic value of the minerals, but rather from their great abundance, and the facility of extracting them, that these mines are to be distinguished from those of Europe. The mean wealth even of the richer veins is not greater than four ounces of silver to the cwt. of ore extracted, whilst many districts of Saxony have at fortunate periods yielded ten and even fifteen ounces, and have often averaged not much below three. We find the produce of most of the silver ores of Freiberg in Saxony to ascend from 3½ths and ½ per cent. to various higher percentages.
The mining district of Freiberg in Saxony abounds in veins of silver, or argentiferous lead. They traverse gneiss rocks, and are generally composed of quartz, lime, and fluor spar. The richest of the Saxon mines, that of Himmelsturz, is situated 2 miles S.E. of Freiberg, and the elevation Mines and of the surface above the level of the sea is 1346 feet; the depth of the mine is 1083 feet. There are five veins, and the principal one is from 1 foot 6 inches to 3 feet in width. The produce of metal is from \( \frac{3}{5} \)ths to nearly \( \frac{1}{2} \) per cent. The total annual produce of ore was formerly 630 tons, yielding 6160 lb. troy of silver, valued at about L.18,000. In 1750 a mass of silver was dug out from a mine near Freiberg, weighing 168 lb.
Hungary contains some rich and extensive silver mines. Those of Schenmitz and Cremnitz have been long celebrated both for their riches and the immense extent of their operations. Some miles to the N.W. of Schenmitz is Koningsberg, another mining town. In the Royal Mine the vein runs between the metallic rock, which forms its hanging side, and the granite, which is its heading side. Transylvania has ruby-silver mines. The circle of Sanz in Bohemia abounds in various metallic ores, among which the ores of silver occasionally predominate. The veins at Catharinaberg traverse gneiss, and generally run in a north and south direction, and parallel to the mountains in which they are situated.
In the Ural and Altai Mountains, especially in the district of Kolyvan, silver is as abundant as in any part of the Old Continent. Travellers mention silver mines also in Armenia, Anatolia, Thibet, China, Cochin-China, and Japan. From China a piece of native silver was brought to St Petersburg of such purity that some coin was struck from it without its passing through the crucible. A story is told with reference to the mine of Schneeberg in Saxony, that a rich vein of silver was discovered in 1478, and so rich a block of the native ore or metal was dug out, that Duke Albert of Saxony descended into the mine and used this block as a dining-table; and when it was melted it produced no less than 44,000 lb. of silver.
The silver mines of Kongsberg in Norway are celebrated, and have been already named. They lie about 52 miles from Christiania, the capital of Norway, and are about 1800 or 2000 feet above the level of the sea. They were first discovered by a peasant in 1624, and were immediately taken possession of by the crown. In 1833 the produce amounted to 29,390 lb. troy, being the greatest ever attained by these mines, and this afforded an surplus of L.44,000. During recent years the yield has been somewhat less; but the profits in the four years 1841 to 1844 inclusive were L.46,787.
Copper has been found in addition to the silver, and at different times an inconsiderable quantity of gold. The geological formation is gneiss, and the lode is in felspar. The Fahlbaand is a certain range of the strata from 10 to 60 fathoms broad, and when it leaves this, the vein does not bear silver; 100 lb. of this Fahlbaand never contain less than \( \frac{1}{4} \)th oz. of silver. The veins become metalliferous as they cease to run parallel with the cleavage of the felspar in the gneiss. The dip of the strata to the east is from 50° to 80°. Among the mines at present worked, the principal is called the "Armens-Grube," so named from being originally assigned to the support of the poor. The entrance to the Armens-Grube is by a high and broad level about 2 English miles long, at the termination of which the shaft commences. There are several levels branching off at various distances from the surface. The descent to the bottom of this mine is by forty-two ladders, averaging 5 fathoms each. The richest pieces of silver have been extracted from this mine; and there are now in the Royal Museum at Copenhagen two specimens, one of 6 feet long, 2 feet broad, and 8 inches thick. Although some of the matrix is attached to this specimen, it is supposed to be nearly all silver. The other specimen, though smaller, is perfectly pure, and is about 18 inches high and 12 in length and breadth.
Little blasting takes place in the rock, but a curious burning method of excavation is employed. On Saturday at noon, when the workmen leave the mine, large quantities of wood are placed against the portion of the rock to be extracted. This being ignited, softens the rock, and on the following Monday the workman commences his labours. In very stubborn rocks gunpowder is used. The excavations are large, and the ventilation is good. Small bundles of wood are ignited instead of candles. Lodging-houses for the miners are near the mines, and they remain there the whole week absent from their families. They are searched previous to their return home. Their pay is equal to about 10d. per day; and they are supplied with provisions at a cheap rate. On the road to the mines we pass the roasting-house, washing-house, and stamps for pounding the ores, all of which are guarded by armed men. About 700 labourers are employed in the mines and at the stamps. The smelting-works are situated in the town, and the smelting takes place twice a year, occupying two months at each period. The fuel consumed is 500 cases of charcoal and 800 fathoms of wood.
The number of silver mines in Sweden has diminished like Sweden, some of the other mines of that country. In 1767 only three were reckoned under exploration. The Sahlra or Sahlberg Mine is now the only one of importance. It is situated in Westmannia, about 23 leagues N.W. of Stockholm, and is very ancient. At present it yields only from 4000 to 5000 marcs of silver per annum. Highly argentiferous lead is its principal product. It is explored to a depth of more than 200 yards. The soundness of the rock has allowed of large excavations and galleries, and in the interior there are winding-machines and carriages drawn by horses for the transport of the ores.
**Platina**
Platina is a most useful but scarce mineral in large quantities. Its refractory and unalterable nature, even when exposed to intense heat, and its resistance to action by salts and acids, fit it in a very peculiar manner for chemical purposes, and accordingly crucibles and caldrons, sometimes of very large size, are made of it. Its polish and freedom from rust and tarnish, its slight dilatability, and the regularity of its expansion for equal increments of heat, render it valuable for pendulums, &c. Medals were struck of it; and in Russia it was introduced as a current coin, but it having been found in greater quantities in Siberia, its value for coining was lowered. From 1831 to 1833 the Russian mines produced 14,000 lb. weight of platinum. The Russian mines are all in the Ural Mountains, and the ore is disseminated in an argillaceous sand of a uran greenish-gray colour, resulting from the disintegration of the surrounding rocks, and constitutes from 1 to 3 parts in 4000 of the sand. Occasionally it has been found in lumps which contain 70 per cent. of platina and 3 to 5 of iridium. One locality contains small flattened grains with 88 per cent. of this valuable metal. It has only been known in Europe since 1748, and was at first brought into the market under the name of white gold. The whole produce of the Urals is sent to St Petersburg.
In the New Continent it is found chiefly in three districts, At Choco, and principally at Choco, in the neighbourhood of Bar-bacoas, and generally on the coasts of the South Sea, or on the western slopes of the Cordilleras of the Andes, between 2° and 6° of N. latitude. The gold washings furnish platina, the former being separated by hand-picking and also by amalgamation. Platina grains are found in Brazil, but always in the alluvial lands that contain gold, particularly in those of Mato-Grosso. Grains are also found in Hayti or St Domingo, and the sand containing them is quartzose and ferruginous.
A remarkable specimen was found in the Ural in 1827, not far from the Demidoff Mines, which weighed 9½ lb. Mines and avoidupois; and at about the same time another was met Mining, with weighing 27 lb. These exceed any mass found in South America. Von Demidoff has also sent several other large masses to St Petersburg, weighing from 10 to 20 lb. From the discovery in 1835 to 1840, about 53,396 lb. were obtained from the Demidoff deposits. (Dickson in Fotherstonhaugh's Journal, No. 3, Sept. 1831.) In 1847 the production had fallen to about 18 lb., representing, at the old price, a value of L352.
The rarity of this valuable metal will render the following notices of its occurrence interesting. In 1847 platina was discovered in the Chapeau Mountain, and in the valley of the Drac, Upper Alps. It was found in a gray copper ore in the transition limestone. This metal has also been found in the alluvium of Columbia and Brazil, in the diorite rock of the high mountains of Columbia, and the serpentine rocks of the Ural. It has also been discovered in Saxony, on the right bank of the River Beus, in the territory of Presles, in a gray carbonate of copper. The quantities were too inconsiderable to justify exportation. In March 1848 it was found at Cavalles in the Mountain of Rousse, in gneiss and talcose schist, and also connected with a green carbonate of copper. The existence of platina in the silver of commerce has been recently certified by a money assayer at Munich, who has likewise obtained more than 500 grains of platina from the slag of the Bavarian coin.
MERCURY OR QUICKSILVER.
This metal is distinguished by its fluidity at common temperatures, its density (=13·6), its silver-blue lustre, and extreme mobility. Native quicksilver occurs in most of the mines of the other mercurial ores, in the form of small drops attached to the rocks, or lodged in the crevices of other ores. Argental mercury, or native silver amalgam, has been found in Hungary, in a canton of Tyrol, in Sweden, Siberia, &c., but only in moderate quantities. Cinnabar, or sulphuret of mercury, is the most abundant and important of the ores, and by sublimation yields the metallic mercury. Vermilion is pure cinnabar, being a compound of mercury and sulphur in nearly the same proportions. The finest crystals come from China and Almaden in Spain, and produce (Klaproth says) 85 per cent. of mercury.
Pliny has recorded two interesting facts—(1.) That the Greeks imported red cinnabar from Almaden 700 years B.C.; and, (2.) That Rome in his time received annually 700,000 lb. from the same mines. They have been worked from time immemorial, and even Theophrastus (300 B.C.) speaks of the cinnabar of Spain.
These mines are the most celebrated for this mineral in the world. The veins extend all the way from the town of Chilian to Almanedelos. Since 1827 they have produced 22,000 cwt. of mercury every year, with a corps of 700 miners and 200 smelters. The veins are so wonderfully rich, that though they have been worked pretty constantly during so many centuries, the mines have hardly exceeded the depth of 330 yards, or something less than a 1000 feet. The lode actually under exploration is from 14 to 16 yards thick, and at the crossing of the veins it becomes thicker still. The whole ore is extracted. It yields in their smelting-works only 10 per cent. upon an average; but there can be no doubt, from the analysis of the ores that nearly one-half of the quicksilver is lost and dispersed in the air, to the great injury of the workmen's health. A certain barbarous apparatus employed in its sublimation, has remained without any material change for the better since the days of the Moorish dominion in Spain. The ores are treated in thirteen double furnaces.
The hill in which the mines are situated is chiefly composed of sandstone, and on its summit rises a crest of naked rocks streaked with cinnabar; indications which unquestionably led to the discovery of the mineral wealth concealed beneath. The whole of the country abounds with ferruginous ores, and in the mines themselves portions of mineral are sometimes found in which iron, quicksilver, and sulphur are blended together. The direction of the hill is from N.E. to S.W., and its height is about 125 feet. Two veins, from 2 to 14 feet wide, varying in richness, cross it in a vertical manner. These veins meet near the most convex part of the hill, when they expand into a bed nearly 100 feet wide, constituting the prodigious mass of ore known as "the Rosary" (El Rosario), the discovery of which was deemed miraculous. A belt of hard stone, from 3 to 4 feet wide, extends across the hill from N. to S., intersecting the veins. Beyond this the line of quicksilver does not pass.
These two veins are the only ones worked at Almaden, and they have already been excavated to such a depth that the drainage has become the heaviest item of expense. Should steam be applied, this charge would be considerably reduced. Thrice during the political contests was Almaden taken by the Carlists, and the last time they partly destroyed the machinery.
The labouring department has been carried on by convicts, each of whom costs the government 2s. a day; whereas peasants would perform double the work at less cost. The quantity of ground bored for shafts, and formed into caverns or resting-places, has not been precisely ascertained, but it is known to be immense. Scenes of the most terrific kind have sometimes occurred within these gloomy recesses. Soon after the junction of the two veins, owing to the confined state of the air, the gaseous exhalations have caught fire, when numbers of the miners have perished. Of this calamity the natives speak in most painful terms. Additional shafts diminish the risk of its recurrence. Remarkable cases of heart-rending misery and oppression have likewise occurred in these abodes of wretchedness. The surrounding scenery is exquisitely picturesque, and sometimes even majestic. The mineral wealth of this interesting hill was not scientifically explored till towards the middle of last century. In 1752 Mr William Bowles, an Englishman and naturalist, was commissioned to make excursions into the interior to survey mines, &c. His first trip was to Almaden, of which he gave some account in a work printed at Madrid in 1775. From the period of his visit the works were conducted on a better principle, but owing to old defects, the mines were inundated a few years afterwards.
About 2 leagues from Almaden another quicksilver mine was discovered in 1755, and commenced working in 1780. In the province of Valencia two quicksilver mines were discovered towards the middle of last century. The "Little Almaden," as it may be called, has produced in some years 1,217,160 lb. avoirdupois, but its average is 304,290 lb.
The quicksilver mines of Idria (a town of Illyria, near the mines Adelsberg, in the Austrian dominions), situated in an alpine valley, are the next largest to those of Almaden. They employ upwards of 600 persons, and produce annually from 3200 to 3500 cwt. of quicksilver, according to one account; but it said that the Austrian government, in order to uphold the price of the metal, has restricted the produce to 150 tons. The workings have been carried to the depth of 280 yards. The memorable fire of 1803 was most disastrous to these mines, and it was only extinguished by drowning all the underground workings. The mercury sublimed in this catastrophe occasioned diseases and nervous tremblings to more than 900 persons in the vicinity. The bituminous sulphuret of mercury appears to be the base of these great explorations. It is of a dark, liver-red hue, of a slaty texture, with straight or twisted plates, and exists in large quantities in the bituminous schists. The produce of these mines has been very large, and it is said that in 56 months, from 1809 to 1813, they yielded 1,419,425 Mines and Mining.
Mines and lb. of mercury, 270,029 lb. of vermilion, and 76,225 lb. of lump cinnabar; besides 6400 lb. of calomel, 2867 lb. of red precipitate, and 2450 lb. of corrosive sublimate.
These mines were discovered in the year 1497. The mountain in which they were first excavated has been exhausted, and the operations are now carried on in an opposite mountain, whence it is said a supply of mercury to almost any extent might be obtained, but the produce is mostly retained for the amalgamation of the Austrian gold and silver ores. A traveller who visited the place states that, having descended by 727 steps, reaching to a depth of 120 fathoms, he arrived at the region where the cinnabar is principally procured. The mining operations are carried on chiefly by galleries, the friable nature of the rock seldom admitting of large chambers. The cinnabar lies in beds from 2 to 6 inches in thickness, and is of a variety of colours from dark to light-red; the native quicksilver being sometimes mixed with it, and sometimes occurring in the intervening strata of earth or stone. The strata yielding the quicksilver do not appear to have any precise direction, and occupy about one-third or one-half of the entire mass of the rock. Proceeding a short distance, the visitor arrived at the galleries where the cinnabar is less common, and where quicksilver is the chief object of search. Here it occurs sometimes imbedded in a friable rock, sometimes in a kind of earth resembling talcose slate, but principally in the former—generally in particles too minute to be discerned by the naked eye. Often when the rock is broken, small globules present themselves, varying up to the size of a common pin's head. They are not distributed at random through the mass, but the matrix in which they occur forms strata usually about one or two inches in thickness.
Descending still lower into the richest part of the mine, the matrix consists almost entirely of talcose earth, and the globules of quicksilver are so large, that when it is broken they roll out and fall to the bottom of the gallery. The labourers, being unable from the state of the atmosphere to work longer, are relieved every four hours in this part, but in other parts they work eight hours. The total number employed was 360, divided into three companies, and their pay was only the usual pay of day-labourers in Germany, viz., from 15 to 17 kreutzers per diem (6d. to 7d.) Several appeared to be suffering from the effects of the mercury.
The masses containing the metal are carried to the washing-rooms, which are situated a few hundred yards from the mines. If the ore is of the earthy kind, it is broken up and laid upon large sieves, by means of which the loose or native quicksilver is separated from the earth. It is then put into little shallow boxes open at both ends, and a little inclined. A gentle stream of water being made to pass over it, and a rake being used, the earthy matter is carried off. Several of these boxes are employed in succession, and by the time the residuum reaches the last of them, it resembles a heavy gray powder, and is sufficiently pure to be carried to the vapour furnace. The stony fragments require only a slight washing to cleanse them from the outward earthly impurities. The furnace is half a mile lower down the valley, and consists of a circular walled building about 40 feet diameter and 60 feet high. The ores being there roasted, the vapour resulting from this operation passes into condensers, where the little drops of mercury collect, and are conducted into a porphyry vessel placed to receive them.
Cinnabar has recently been discovered and mined in California, where it occurs in a quartz vein in clay-slate. The veins are vertical, but the slates themselves lean considerably eastward. Great importance is attached to this discovery by the Californian miners.
The ordinary method of reducing the ores of quicksilver is by distillation. In some places the richer ores are burnt separately; but it is more common, and thought more economical, to mix the richer with the poorer ores, and expose the whole mass together to the action of heat in closed retorts, which also contain a certain proportion of limestone. The retorts filled with the mixture of ore and limestone are ranged, to the number of twenty or upwards, in recesses of a furnace, and heat being applied, each retort is made to communicate with a vessel of water, in which the vapours of the mercury are condensed.
The imports of mercury into this county, chiefly from Almaden, are about 2,200,000 lb. annually, of which little more than an eighth is retained for home consumption. The remainder is exported principally to South America and Mexico, the United States, and the East Indies; while smaller shipments are made to Russia, Belgium, and other countries.
Copper.
(On copper as a metal, see the article Copper.) Some of the principal localities for copper may be noticed before we treat of the mines of this metal in our own country.
The copper ores from Australia are strictly analogous to Australia, those from the Ural. They occur in nodules disseminated in a slightly coherent sandstone, or ochre clay, and the surface of the nodules is studded over with crystals, the interstices between which are filled with clay or sand. Some of the nodules are of large size; one of them from Burra-Burra measuring 2½ feet by 2 feet superficial, with a thickness of 6 inches. The principal mass in this specimen consists of oxide of copper, with the green and blue carbonates of the same metal forming an external coating; but the three minerals are not superimposed in zones, the red oxide, although principally in the centre, sending out shoots in every direction. A little native copper occurs with the oxide. The Burra-Burra mines have yielded 56,428 tons of ore, averaging 40 per cent. of copper, between the time of their first opening in 1845 to the end of 1850, at which date more than 1000 workmen were employed. For some time these mines have been reported to be unworked, owing to inundations or desertion of miners to the gold diggings; but they are now said to be at work again, and highly productive. Many of the shares are held by British capitalists. The mine was commenced 5th September 1845, and the following are its returns of ore for the first five years:
| Year | Tons | Cwt. | |------|------|------| | 1846 | 6,359 | Total produce in five years, 56,428 tons | | 1847 | 10,794 | 17 cts. of copper | | 1848 | 12,751 | 11 cts. of copper | | 1849 | 7,739 | 10 cts.; value of same | | 1850 | 18,632 | 9 cts.; L738,168. |
The ores yielded from 30 to 70 per cent. of copper.
No copper mines have ever yielded such rates of profit as the Burra-Burra. At a meeting held in April 1850, it was stated that the amount of paid-up capital was only £1,12,320, on which dividends had been paid, from June 1847 to March 1850, amounting to £1,72,480, equalling a total profit of 1400 per cent. upon the capital. In several of the dividends, in particular, the profit was at the rate of 200 per cent. upon the capital, and in none less than 50 per cent. The balance-sheet showed an undivided profit of £99,779, thus making the total profits since the commencement £272,259. In five years the shareholders had received net dividends amounting to nineteen times the money they advanced.
The most productive deposits of copper in the United States are those lying upon the shores of Lake Superior. The discovery of these was made many years ago, but the first scientific researches commenced only in 1842 by a geological surveyor attached to the government of the state of Michigan, and have been continued by Mr Jackson, who has made a detailed study of the district. There the native copper exists in two distinct deposits, one towards the northern extremity of the state of Michigan, at Keweenaw Point, which forms a projecting headland towards the middle of the shore of Lake Superior; and the other in Isle Royale, situated in the lake, about 50 miles N. of Keweenaw Point. This island, which ranges S.E. and N.W., lies exactly parallel to Cape Keweenaw, and to the strike of the beds of which it is composed. It presents also a geological construction identical with that of the shores of the lake. The two deposits occur in the same formation, and under circumstances precisely similar. Mr Jackson's geological map shows that the Michigan shore of the lake consists of granite, trappean rock, and red sandstone belonging to the Lower Silurian series. The sandstone and trap form parallel bands running due N.E. and S.W.
Native copper and silver are found at Cape Keweenaw and Isle Royale only in the trap formation; all the important veins forming together a narrow zone in the amygdaloid. When a vein of copper penetrates the trap, it at once thins out, and only affords a scanty film not worth working. The sandstone and conglomerate form also another limit of the metalliciferous band, and when the veins do not terminate at the contact of the sandstone, the part extending into this rock is filled with calc-spar instead of copper; hence it results that the thickness of the amygdaloid band intervening between the trap itself and the sandstone becomes the limit of the cupriferous veins, which are of the most solid metallic form. The depth of the veins is unknown. It is uncertain if they extend below the sandstone. At Keweenaw Point the cupriferous zone may be about 120 miles in length; and in Isle Royale it ranges through the whole extent of the island, which is about 45 miles long. The richer portions are unequally distributed. Mr Jackson (Geological and Mineralogical Reports, by Charles Jackson, November 1849) has made numerous researches for several years, and states the direction of the veins, of which he has explored more than a hundred. In Copper Fall Mine they take a direction from N. 25° W. to N. 30° W., and S. 25° to 30° E.; almost at right angles to the line of separation of the trap and sandstone; and the dip is here 70° W. These veins are 18 inches wide, of which metallic copper occupies a fourth part. Mr Jackson had seen a mass 20 feet long, 9 feet wide, and from 4 to 6 inches thick, taken from these mines; the mass weighed about 10 tons.
The Cliffe Mine, the deepest and most extensive, commenced in 1848. It has repaid its original capital four times over. The lode is regular and continuous, and improves to 500 feet in depth. The produce of other mines for one year had been nearly 43 tons (95,994 lb.) of ore, containing 70 per cent. of metal, or about 30 tons of copper in all. The annual produce of Lake Superior mines has been 3000 tons. Among the masses of copper are mentioned four, the respective weights of which were 7018 lb., 7484 lb., 7678 lb., and 14,000 lb. One very extraordinary lump of copper was found on these shores which was estimated to weigh about 80 tons, and measured 50 feet in length, 6 in depth, and averaged 6 inches in thickness.
In Siberia there are two principal copper mines, situated in the Ural Mountains. From one of these, in the central part of the chain, have come those magnificent specimens of malachite which have often excited wonder. Two large polished doors of Russian malachite, and several minor masses, were displayed in the Great Exhibition of London in 1851, and a splendid malachite vase presented to the Queen is kept in Windsor Castle.
One of the most celebrated and productive copper mines is that of Fahlun in Sweden. It is said to have been explored before the Christian era. In its greatest prosperity it yielded about 5000 tons of copper per annum; it now furnishes about one-seventh of that quantity, and about 70,000 lb. of lead, 50 oz. of silver, and 3 or 4 oz. of gold. The mining district occupies a space of 9 leagues in length by 2½ in breadth, and is surrounded by a reddish granite, succeeded by a micaceous rock. The principal mass, which is of enormous dimensions, consists of iron and copper pyrites, lying in a vertical position from N.W. to S.E. along the valley in which it is deposited. Here there is an immense opening or gulph of 840 feet in length, 720 in breadth, and 240 feet in depth, which was produced in the year 1687 by the falling in of a mass, in consequence of the unskilful manner of mining. The mass of ore lies in the form of an inverted cone, and the excavation has been carried to a depth of more than 200 fathoms. Latterly the operations have been carried on upon a more limited scale. In this mine Gustavus Vasa, when driven from his throne, worked for the means of subsistence. In the mine of Garpenberg, 18 leagues from Fahlun, there are fourteen veins in a vertical position, and all parallel to one another.
Cornwall—where before 1712 the yellow copper ore was Cornwall thrown aside—now furnishes nine-tenths of the copper of our own country. Altogether it is found in larger or smaller quantities in nine counties of England. The number of copper mines in England is about 220; in Wales, 12; in Ireland, 15; in all 247. In this number are included several mines producing small quantities, and about 50 are excluded which do not produce any ore. The following tables will show the advance of Cornish copper mining:
### Produce of Cornish Copper Mines from the Year 1745 to 1800, in Decennial Periods.
| Years | Tons of ore | Average price per ton | Amount realized | |-------|-------------|-----------------------|----------------| | From 1745 to 1755 | 98,790 | L 7 s 0 | 731,457 | | " 1755 to 1765 | 169,699 | L 7 s 6 | 1,243,945 | | " 1765 to 1775 | 264,273 | L 6 14 6 | 1,778,337 | | " 1775 to 1785 | 304,133 | L 6 3 0 | 1,827,106 | | " 1785 to 1795 | Not known | — | — | | " 1795 to 1800 | 249,834 | L 8 9 6 | 2,177,724 |
The next table exhibits the annual produce and sales of copper ores for eight recent years, with the quantity of copper yielded by the ores:
| Years | Ores | Copper yielded | Value | |-------|------|---------------|-------| | 1848 | 147,701 | 12,241 | L 19 2 5 | 720,020 | | 1849 | 146,236 | 11,683 | L 13 0 22 | 763,614 | | 1850 | 155,025 | 12,253 | L 10 2 21 | 840,410 | | 1851 | 150,380 | 11,807 | L 8 2 18 | 782,947 | | 1852 | 165,593 | 11,776 | L 17 2 24 | 975,754 | | 1853 | 181,944 | 11,913 | L 12 0 12 | 1,155,167 | | 1854 | 184,588 | 11,979 | L 4 2 21 | 1,192,966 | | 1855 | 195,193 | 11,578 | L 11 0 23 | 1,263,739 |
The quantities of copper ore bought by private contract by the great copper-smelting firms could not be included in the above table. The amount of sales at Swansea, in this form, in the year 1853, were 24,633 tons ore, which yielded 5875 tons 2 qrs. 11 lb. of copper. This quantity was bought by about ten firms or companies. The subjoined table displays the total quantities of copper smelted in this county for the last three years, the quantities bought in Cornwall, at Swansea, and by private contract, being distinguished:
| Year | Cornwall | Swansea | Private Contract | Total | |------|----------|---------|-----------------|-------| | 1853 | 11,913 | 4,559 | 5,875 | 22,348 | | 1854 | 11,064 | 4,729 | 5,426 | 22,217 | | 1855 | 12,678 | 5,926 | 7,440 | 25,945 | It will thus be seen that the production of copper during 1855 in this country shows a large increase.
The mode of mining for copper ores has already been treated of above under "Practice of Mining." We have only therefore to add in this place, that the greatest enterprise has been shown in Cornwall, both in copper and tin mining. Some of the Cornish copper mines are remarkable, and chiefly that named Botallack, established at the western extremity of the great copper and tin lodes, conjoined with lead, which run eastward through Cornwall. This mine was formerly worked only for tin, and was nearly abandoned in 1841, when, however, copper was found. In 1853 it yielded 1001 tons of copper ore, or 93 tons 8 cwt. of copper, and 147 tons 9 cwt. of black tin. The value of the copper was L9248, and that of the tin L8656.
At this and two other small mines in the vicinity, the hardihood of the miners has tempted them to follow the ore upwards, so close to the sea, that small openings were thought to have been made, and a covering of wood and cement was applied. A detailed account of the processes for dressing copper and tin ores will be found in Cornwall; its Mines and Miners, pp. 203, &c. In a table in p. 232 of that book, we observe that the average produce of the Cornish copper ores for eight years was from 7½ to 8½ per cent. of metal to the ores.
The first process in dressing copper ores, so as to fit them for the smelter, is to throw aside the dregs or rubbish, and this is cleverly performed by girls of seven or eight years of age, for 3d. or 4d. a-day. The largest fragments of ore are then cobbled, or broken into smaller pieces, by women. After being again picked, they are given to the "maidens" (as girls of sixteen or seventeen are named), who buck the ore with a bucking-iron or flat hammer, by which they bruise the pieces to a size not exceeding the top of the finger. The ores are now given to boys, who jig them, or shake them in a sieve under water, by which means the ore or heavy part keeps at the bottom, whilst the spurr or refuse is scraped from the top. That portion which passes through the sieve is also stirred about in water, the lighter parts being thrown on the surface; and the ores thus dressed being put into large heaps of about 100 tons each, are then made ready for the market. The copper ores of Cornwall are all shipped for Wales, and mostly for Swansea, to be smelted there, it being cheaper and better to carry the ores to the coals than the coals to the ores. (For the methods of smelting, see Copper Smelting.)
The most productive copper mines now in Cornwall are the Devon Great Consols, Carn Brea, Consolidated, United Fowey Consols, Par Consols. Some particulars of a more general nature respecting one of these, viz., the Consolidated Mines, will illustrate the extensive business of so great a concern:
| Consolidated Mines in 1836. | |-----------------------------| | Quantities of ore raised: | | Copper, 18,493½ tons. L143,039 12 5 | | Tin, 2,533 0 10 | | Arsenic, 144 7 10 | | Lord's dues for rent for same. | L145,717 1 11 | | Value of ore, deducting dues. | L139,645 10 7 | | Total expenses for the year. | L102,007 12 1 | | Total profit on the mines. | L37,637 18 6 |
The following are the sales of copper ores in Cornwall for the three quarters of 1856:
| Quarters ending | Tons. | Proceeds. | Amount. | Average Price per Ton. | Product of Fine Copper. | |-----------------|-------|-----------|---------|------------------------|------------------------| | Mar. 31, 1856 | 53,934| 6,202 | 317,337| 17 6 | 5 17 8 | | June 30, | 54,273| 6,311 | 308,633| 18 0 | 5 13 8 | | Sept. 30, | 49,636| 6,976 | 299,273| 16 0 | 6 0 7 |
Details of Expenses (some of the principal items):
| Item | Amount | |-----------------------------|--------| | Agents' salaries | L3,343 19 3 | | Tutwork bargains | 26,177 3 8 | | Materials | 15,008 6 4 | | Engine or water cost (with rent of water, L405,134.) | 15,415 7 4 | | Expenses on ores | 7,803 8 7 | | Tribute, sublet, and balances | 25,030 17 0 |
Number of Persons Employed:
| Occupation | Number | |-----------------------------|--------| | Agents | 28 | | Tutwork men (working by task for a fixed price) | 441 | | Tributaries (working for an agreed proportion of the ore raised) | 302 | | Surface men | 335 | | Boys underground | 109 | | Boys at surface | 327 | | Females | 755 |
Total: 2,387
Rate of Wages to Work-people:
| Occupation | Per Month. | Per Month. | |-----------------------------|------------|------------| | Tutwork men | L3 11 6 | L0 15 0 | | Tributaries | 4 5 | 0 | | Surface labourers | 2 6 | 0 | | Women and girls above | 17 | 0 18 0 | | Girls from 14 to 17 | | | | Girls from 12 to 14 | | | | Girls from 9 to 12 | | | | Boys above 12 | | | | Boys under 12 | | |
The usual rate of wages should be estimated lower, as there was a great demand for miners in 1836.
TIN.
Cornwall and Devon afford all the tin yielded in the United Kingdom. Its foreign repositories are Bohemia and Saxony in Europe, and Malacca and Banca in Asia. One of the richest known deposits of tin is in the province of Tenasserim, on the east side of the Gulf of Martaban, in the Malayan Peninsula. There the richest layer of tin lies in a stratum of sand and gravel 8 or 10 feet thick, in which masses of oxide of tin are often found of the size of a pigeon's egg. The ores are also found in large caves near the surface; and although actively mined for many centuries, there is still easy access to unexhausted portions. The mines in the island of Junkseylon sometimes yield 800 tons per annum. The mines in the island of Banca, to the east of Sumatra, discovered in 1710, are said to have furnished in some years nearly 3500 tons of tin. It is found in the alluvial tracts through every part of the island, but rarely more than 25 feet below the surface. Great deposits of tin occur in the Siberian mining district of Nertshinsk, near the desert of the Great Gobi, and near Oruro in Bolivia. The Peruvian and other foreign tin contains large admixtures of tungstates of iron and lime, which depreciate its value; but an eminent metallurgist has discovered and patented a process by which the separation of these can be easily effected.
The tin mine of Altenberg in Saxony is remarkable for saxony, an interlaced mass of ramifying veins, termed a stockwerkere, in a primitive porphyry (superposed upon gneiss), through which the ore is disseminated in minute particles. This mine has been wrought since the year 1458. In the year 1620 it was worked by twenty-one independent companies in a most irregular manner, so that it was damaged by a dreadful fall of the roofs to a depth of 170 fathoms. This mine yielded, some years ago, annually 400,000 quintals of tin ore, affording 1600 Leipsic quintals of tin, this amount being four-fifths of the whole furnished by the district of Altenberg.
A somewhat similar deposit of tin occurs in the soft Cornwall. Mines and decomposed granite of Carclaze Tin Mine, near St Austell, Cornwall. This singular mine has been wrought for nearly 400 years, and is the only one entirely open to the day. It consists of a large excavation of a mile in circuit. Its exact dimensions are 250 fathoms in length, 100 fathoms in breadth, and 22 in depth. The excavation occupies 5 statute acres, the solid contents are 63,000 cubic fathoms, and more than a million tons have been removed. There are no shafts or other usual appurtenances of a deep mine. The ground is almost wholly composed of decomposed granite, through which runs a numerous assemblage of schorl and quartz lodes in the usual direction. These contain the tin minutely disseminated. The ore is separated from the stone by repeated washings in little streams, conducted to and moving various water-wheels arranged in the bottom, and along the sides of the excavation.
In Cornwall the number of tin mines is about 130, and some are included in this number which produce copper as well as tin. Tin was probably obtained in this county at an earlier period than any other metal. Mr Carne has given a table of the Cornish produce of tin from 1750 to 1837; and Mr Hunt has formed a table of the produce of British tin from 1800 to 1855; thus affording records of tin mines of a more authentic kind than we possess of other metals. We are thus enabled to trace the course of the produce of this metal, of which a few specimens may be quoted:
| Year | Tons | |------|------| | 1800 | 2522 | | 1805 | 2785 | | 1810 | 2035 | | 1815 | 2941 | | 1820 | 2990 | | 1825 | 4358 | | 1830 | 4444 | | 1835 | 4228 | | 1848 | 6613 | | 1849 | 6552 | | 1850 | 6729 | | 1855 | 6000 |
It will be observed that the produce of tin has been steadily progressing, notwithstanding the precarious nature of the search for it, and the various fluctuations of mining.
The following are some of the principal Cornish mines, with their produce in 1855:
| Name of Mine | Quantities of Black Tin | Value | |--------------|------------------------|-------| | Penzance | 322 | 18,084 | | | 27 | 17,855 | | | 217 | 15,749 | | | 229 | 12,668 | | | 149 | 9,931 | | | 388 | 6,389 | | | 203 | 16,940 | | | 104 | 6,670 | | | 233 | 15,655 | | | 59 | 5,991 | | | 254 | 17,748 |
Mr Carne informs us, that the prices paid to the tinner in Cornwall between the years 1746 and 1788 varied from 60s. to 72s. the cwt. We find that from 1783, when the price was L4, 1s. 7d. per cwt., it varied considerably, reaching in 1810, L7, 9s. 8d. per cwt., and falling in 1825 to L4, 16s. 6d. per cwt. The annexed table gives the annual value of the tin ore raised in England within the last three years, and of the tin:
| Years | Tin Ore raised | Average value per Ton | Total value of Ore | Estimated value of Tin per Ton | Estimated value of Tin | |-------|---------------|-----------------------|--------------------|-------------------------------|-----------------------| | 1853 | 8866 | 0 0 68 | 593,088 | 112 to 118 | 700,000 | | 1854 | 8747 | 0 0 64 | 559,808 | 112 to 118 | 690,000 | | 1855 | 8947 | 0 0 68 | 608,896 | | |
In 1855 the average prices of tin were—
- English blocks ........................................... L125 0 0 - ... bars .................................................. 126 0 0 - ... refined ............................................... 129 0 0
The existence of tin in Australia and Van Diemen's Land is known; and in the tin forwarded to this country from Victoria a considerable quantity of gold has been found. It mostly lies in grains in sand, and is analogous to our stream-tin.
In this country there has not been for a considerable period a discovery of any new locality of tin. The stream-works are by no means so productive as formerly, and the fly-mines are being worked at a constantly increasing cost; yet the demand for tin in our white-metal manufactories is constantly increasing. The principal importations of tin to our country are from Singapore, Java, and the East Indies, and Holland. The total imports to us from Singapore during eleven recent years (from 1844 to 1854 inclusive) have amounted to 8303 tons of tin; from the East India Company's territories, during the same period, 2738 tons; and from Holland, for the same years, 4567 tons. In 1855 we imported 1612 tons of tin; and exported 1337 tons of British tin, also 280 tons of foreign tin.
It remains to speak of the processes for dressing tin ores. Dressing these commence with cleaning and sorting, and then proceed to washing and stamping, and finally to calcination in the "burning-house," and to smelting. The same great principle rules these processes that rules in dressing copper or lead ores, viz., the agitation of the mass reduced to fragments, so that the metal, by its much greater specific gravity, shall separate and sink down from the lighter earthy matter. The stamping is in the best mines performed by stamps or pestles of wood, carrying lifting-bars, and terminating in a lump of cast-iron called the head, and weighing 2½ or 3 cwt. A turning-shaft communicates motion to the stamps by cams, which are so arranged as to secure the falling of the second stamp while the first and third are uplifted. Each stamp gives 28 strokes per minute. With six batteries of six pestles each, at Poldice Mine 120 bags of ore are stamped in 12 hours, each bag containing 18 gallons of 282 cubic inches, measuring altogether 352 cubic feet and 864 cubic inches. At Boscastle Tin Mine there is a 24-inch stamping-engine, to which are attached 48 heads of stamps, and there are 20 heads of stamps worked by water-power. At Botallack the tin stuff is returned by water-stamps of 24 heads. At Levant Tin Mine there is a 34-inch stamping-engine, working 64 heads of stamps. At Polherro Consols one large engine drives 120 heads at a time. By repeated pulverization, washing, and agitation, the ores may be obtained in a very fine state. As tin is often combined with wolfram, tungstate of iron, and other materials, which cannot, owing to their greater specific gravity, be so easily separated from the ores of tin as earthy matter, a new process has been invented by Mr Oxland, by which wolfram, &c., may be separated, and eventually the wolfram is saleable separately.
The ores of tin raised in Cornwall and Devon are always smelted within those counties, their transportation being prohibited. The market price of tin has lately risen considerably, and it still remains at a high figure; the mines of this metal are therefore more flourishing than usual. Tin ore is worth from L56 to L68 per ton. In its natural state, when dressed, the ore is called "black tin," to distinguish it from "white tin," which term is applied to tin in its smelted and refined state.
LEAD.
Before speaking more particularly of the lead deposits of United our own country, we may briefly allude to those of other States, countries. One of the most remarkable lead deposits in the world is found in the western section of the United Mines and Mining.
States, particularly in Washington, Jefferson, and Madison counties, Missouri; and at Galena in the N.W. part of Illinois; in Iowa and the territory of Wisconsin. In this latter district the length of the lead deposit is 87 miles and its width 54, covering 80 townships, or 2880 square miles. In 1839 thirty million pounds of lead were smelted from this deposit; and during the eight subsequent years the smelted quantity varied from 72 millions to 54 millions of pounds. It is thought that it would readily yield annually 150 millions of pounds.
France.
France possesses considerable deposits of lead, and some very old mines, although the development of these is not commensurate with their value. The most important are those of Poullaouen and Huegloet in the department of Finistere. These have been worked in two parallel veins, and have been known for upwards of three centuries. In 1816 they furnished 500 tons of lead. The mine of Pontgibaud is well known to English adventurers, and contains nine lodes or veins. It was worked as early as Poullaouen, although the last workings commenced in 1825. The ore is an argentiferous galena, of which 7800 tons have been extracted annually, which extraction yields 1077 tons in dressed ore, and 980 tons in "schlick." Vialas yields 81 tons of lead, 20 tons of litharge, and 12 cwt. of fine silver. The Pont Pean Mine is working upon a vein which is known for a run of 1½ mile, and the works have reached a depth of 78 fathoms. Here they obtain about 244 tons of dressed ore, which is sold for about L1400. The produce of the other lead mines is insignificant.
Germany.
Germany has also some valuable mines of lead, particularly in Saxony and in the Hartz. These are so rich in silver as to cause the lead to be almost overlooked. Hungary and Bohemia yield a good argentiferous lead. The mines of Bleiberg and Villach in Carinthia, where galena or sulphuret of lead is the prevailing ore, furnish the finest specimens of the molybdate of lead. At Tarnowitz in Silesia there is a remarkable deposition of lead ore, the beds in which it is distributed reposing in horizontal strata of compact limestone, which contains petrified shells. The lead ore is there deposited in veins, in rounded masses, and in small grains. The Ural Mountains in the Russian empire, so rich in other mineral productions, do not seem to contain lead; a chromate of lead is found in the gold mine of Beresov, where it is seen in a small vein of ferruginous quartz traversing a gneiss rock of a reddish colour.
Spain.
Spain possesses numerous and valuable lead mines. The most important are those of Linares, which are situated to the east of Bailen, near the Sierra Morena. They have been long celebrated, and probably no known mineral field is naturally so rich in lead as this. The lead deposits, associated with much silver, and occasionally copper ores, occur in each of the local limestone districts. The expense and difficulty of conveying stores to the mines, and the ore to the market, are almost the only impediments to the prosperity of these mines, but they are sufficient to check it, excepting when lead bears a high price in the market. The lead ores of Spain are highly argentiferous, and of late years a considerable quantity of this ore has been imported by us from Spain. In the year 1851 we received 14,402 tons of lead. In 1854 the imports from Spain were 11,337 tons of lead.
Sweden.
The lead of Sweden is highly argentiferous, and is worked chiefly with a view to the silver. In Daouria are numerous mines lying in a rich transition limestone which rests on primitive rocks, the lead being neglected in consideration of the silver. It is thought that the galena of the primitive formations contains more silver than that of the calcareous or carboniferous limestones.
Produce of British lead mines.
It has often been supposed that England, so rich in regard to iron, copper, and tin, is comparatively poor in lead, or that her lead mines are of secondary importance; but this is so far from being correct, that it will be found that our Mines and own country supplies more lead than any other in the Mining world. We do not speak of the amount contained, but of that raised. The following table will show the amount of lead ore raised, and lead smelted, in the United Kingdom during nine recent years; and the table subsequent to it being included, we shall have the quantities for the last ten years:
| Year | Lead Ore | Lead | |------|----------|------| | 1845 | 78,267 | 52,695 | | 1846 | 74,564 | 50,161 | | 1847 | 83,747 | 55,703 | | 1848 | 77,864 | 54,853 | | 1849 | 86,773 | 58,703 | | 1850 | 93,043 | 64,572 | | 1851 | 101,964 | 65,110 | | 1852 | 91,236 | 64,987 | | 1853 | 85,121 | 61,021 |
The annexed table will still further exhibit the lead districts of the United Kingdom, with the produce of each in ore and metal, from returns for one year, viz., 1854, being the latest as yet made:
Summary of Lead and Silver Produce of Great Britain and Ireland.
| County | Lead Ore | Lead | Silver | |-----------------|----------|------|--------| | Cornwall | 7,469 | 5,905| 179,676| | Devonshire | 4,139 | 2,612| 119,288| | Cumberland | 9,890 | 6,662| 42,020 | | Durham and Northumberland | 22,329 | 16,669 | 78,577 | | Westmoreland | 383 | 289 | 80 | | Derbyshire | 7,554 | 4,508| ... | | Shropshire | 3,797 | 2,765| 184 | | Yorkshire | 9,244 | 6,476| ... | | Cardiganshire | 7,634 | 4,948| 33,418 | | Carmarthenshire | 901 | 666 | ... | | Denbighshire | 1,324 | 1,363| 1,455 | | Flintshire | 7,027 | 5,408| 28,588 | | Montgomeryshire | 1,184 | 894 | 3,298 | | Merionethshire | 98 | 63 | ... | | Glamorganshire | 62 | 45 | 352 | | IRELAND | 3,069 | 2,210| 18,096 | | SCOTLAND | 1,753 | 1,279| 5,426 | | ISLE OF MAN | 2,800 | 2,137| 52,262 | | | 90,548 | 63,929| 562,659|
The number of mines is 322. They give employment to 14,499 male persons in England, to 5982 in Wales, and to 897 in Scotland; as well as to 371 females employed in works at the surface. The total is 21,749 persons. The price of pig lead in the London market in 1853 was L23, 10s. per ton; in 1854 it was the same, and in 1855 it was L24 per ton. It has been rising from 1844, when it was L17, 5s. per ton.
When we examine the returns of the principal lead mines in each of the above districts, we find considerable differences in the yield of the several mines in different years. Thus, in 1850 the richest lead mine in Cornwall was East Huel Rose, then yielding 4206 tons of ore, equalling 2524 tons of lead; but in the returns of 1854 we observe the same mine yields only 1215 tons of ore, equalling 828 tons 5 cwt. of lead. On the other hand, we find South Tamar Consols Mine in Devonshire yielding in 1850 only 477 tons of ore, but in 1854 as much as 1469 tons 19 cwt. Another instance of this difference for the same two years is noticeable in the Brownley Hill Mine in Cumberland, which in 1850 produced 263 tons 4 cwt. of ore, while in 1854 it yielded no less than 1722 tons of ore. To take a Mines and mine in the north of England, Derwent produced in 1850 Mining, the amount of 1770 tons 1 cwt.; in 1854 only 1000 tons. The above-named mines are about the most productive in their respective districts for one or other of the two years named. The galena of the Beer-Alston mines in Devon has sometimes contained from 80 to 140 ounces of silver per ton of lead.
The lead ores most interesting in the arts are:—1. Sulphuret (or biaulphuret) of lead (specific gravity from 7-4 to 7-6), or, as it is commonly called, galena, almost the only lead ore which occurs in sufficiently large masses to become the object of mining and metallurgy. It is found amongst the older rocks, as talc-schists and clay-slates, but is much more abundant among the transition rocks where it exists in interrupted beds, masses, and veins. The blackish transition limestone is that rock which of all others contains most galena in Normandy, the Hartz, and in Sweden. 2. Seleniuret of lead. 3. Native minium, or red lead. 4. Carbonate of lead, or white lead. 6. Vitreous lead, or sulphate of lead. 7. Green lead, or phosphate of lead. 8. Chromate of lead.
In our own country the lead of Cornwall and Devon is found in veins in kilias or clay-slate. The galena of the Leadhills of Scotland occurs in a transition slate of a similar character. But in North Wales, as well as in Cumberland and the whole northern lead district, and in Derbyshire, the galena occurs in the carboniferous limestone which underlies the coal measures. Technically speaking, galena occurs in plutonic, metamorphic, and fossiliferous sedimentary deposits. A specimen of a lead vein from the Laxey Mines (Isle of Man) represents the total thickness of the lode, which amounts to nearly 23½ inches. The specimen is about 5 feet long by 30 inches wide. It consists of five solid layers or veins of galena separated by thin bands of sulphate of barytes. It was in the Great Exhibition, and was presented to the Museum of Practical Geology in London.
A magnificent lump of galena from the mines of Snailbatch or Snailbeach near Shrewsbury, is still more curious. It is composed of an assemblage of large cubes of galena measuring 3½ inches a side, and of rhombohedral crystals of violet-coloured calc-spar 9½ inches long, the edges replaced by large facets. This specimen measured above 55 inches by 43½ inches, its thickness being 14 inches. (For the metallurgy, &c., of lead, see the article Lead.)
The great lead-mining country of the north of England lies around the junctions of the counties of Northumberland, Cumberland, Westmoreland, Durham, and Yorkshire. It comprises Alston Moor, the mountain ridge of Cross Fell, the dales of Derwent, East and West Allendale, Weardale, and Teesdale. The three rivers—the Tyne, the Wear, and the Tees—take their rise from the bold and lofty hills in that locality.
The coal beds so extensively worked at Newcastle-on-Tyne and in the Durham coal district gradually rise to the west, and one by one crop out, or basset, according to the undulations of the country. At length at about 20 miles W. of the German Ocean, the lowest of the beds crops out, and from beneath it gradually appear the limestone strata, which continue to rise nearly coincidently with the general rise of the country, until they reach the summit of Cross Fell (2901 feet). This general and very gradual inclination of the strata is a feature of the greatest importance in the practice of mining. In a thickness of about 2000 feet of the alternating beds of sandstone, clay, and limestone, which form the mining districts of Allendale, Alston, and Weardale, there is one single bed of limestone, named the "Great Limestone," the metallic veins in which have produced nearly, if not quite as much, lead ore as all the other strata put together. This stratum lies at a depth of about 850 feet below the summit of Kilhope Law. A little more than 2 miles eastward of this, at Allenheads, the top of the Great Limestone is 230 feet from the top of a shaft called Gin-Hill Shaft. Its thickness, which is tolerably uniform over several hundred square miles of country, is about 60 feet.
Kilhope Law is a hill rising 2200 feet above the level of the sea, on the boundary line of the counties of Northumberland and Durham, and is the highest point in Durham. About a quarter of a mile to the W. of Kilhope Law, the great limestone and all other associated beds are thrown down a depth of about 150 feet for a space of nearly 700 feet; and again, at the distance of nearly a mile from Allenheads, a vast dislocation takes place by which the Great Limestone is brought nearly to the surface, the amount of displacement being about 400 feet. By far the most extensive portions of the workings of the Allenheads Mines are situated in the Great Limestone. These mines being for the most part at depths from the surface varying from 200 to 600 feet, they are drained by ordinary water-wheels, and partly by the new hydraulic engines of Armstrong, four of which are now in use for draining and other mining purposes at the Allenheads mines. The most extensive mineral property in England, in the hands of a single individual, is in the mines of East and West Allendale and Weardale, belonging to Mr Wentworth Blackett Beaumont, M.P. The produce from these mines in 1854 was 12,220 tons of lead ore, or 9200 tons of lead, and 49,000 ounces of silver. The pigs of lead manufactured from the produce of these mines bear the well-known mark "W. B.," and weigh each 1½ cwt. The number of pigs commonly made in one year, if laid in a continuous line, would extend upwards of 70 miles. The produce of the Beaumont mines is about one-sixth of the total amount of lead raised in Britain, and about one-tenth of that of all Europe.
This part of the country happens to be at once about the centre of our island, and by far the most elevated part; districts, and is thickly peopled. Scattered over hills and dales, which present to the eye a succession of verdant fields and heathy moors, are to be found some thousands of inhabitants, nearly the whole of them being employed either in lead mines or in smelting mills, or indirectly deriving a livelihood from the lead-mining business. Allenheads forms a central position in the midst of these mines. The agent's house is 1400 feet above the level of the sea, and is said to be the highest house of its magnitude in Great Britain; not many even of the shepherds' cottages and other moorland habitations in England having a greater elevation.
The mining district of Alston Moor (situated at the south-eastern extremity of the county of Cumberland) comprises the whole of the parish of Alston; but by far the most extensive and productive mines are situated in the vale of the small river Trent, a tributary of the Lyne. In the vale of the Lyne, from Alston to Lynehead, are also numerous mines; and trials for mines and workings, which occasionally yield lead, are seen all over the parish. This mining district belongs principally to the commissioners of Greenwich Hospital, who let the mining ground on leases to various companies of adventurers, by whom the mines are wrought. The principal of these is the London Lead Company, producing about one-half of the ore raised in the manor.
One of the most celebrated of the Alston Moor mines, Hudgill Burn, was commenced by the Flow Edge Mining Company; a level driven 250 fathoms in the bed under the Great Limestone, and found only two weak veins. They sunk shafts and pursued other operations, discovering only
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1 Plumbago, graphite, or black lead, is one of the numerous forms in which carbon occurs, and is familiar to us in lead pencils. The celebrated Borrowdale mines, in Cumberland, supplied pieces which could be sliced and used in the natural state. It is not a lead ore. Mines and another small vein, which they explored for 20 fathoms, and produced but a few trifling specimens of ore not worth washing and cleansing. Having lost L2,000, this company abandoned the undertaking, which then lay neglected for eight years. In 1812 some miners obtained leave to continue the search, and their success was so great that their discovery has proved a source of wealth to themselves, and has afforded employment to vast numbers of the labouring classes.
A work of great interest in this district is the Nent Force Level, which drains the numerous mines of Alston Moor. This is a stupendous aqueduct 9 feet broad, and in some places from 16 to 20 feet high. For more than 3 miles it passes under the course of the River Nent to Nentsbury engine shaft, and is navigated underground by long narrow boats. At the distance of a mile in the interior, daylight is seen at the mouth like a star, which continually enlarges as the passenger proceeds outwards, until he finds himself in open daylight.
Lead veins. The veins of lead are similar in their nature to the lodes of copper, tin, &c., in Cornwall, though the accompanying strata are different. A lead vein may be popularly described as a crack descending in a nearly vertical direction through the various beds, which have usually been separated not only a few inches or feet (forming the thickness of the vein), and subsequently filled with vein-stone, rider, and galena), but also by a vertical shift or dislocation, so that a vein may be between limestone on one side and sandstone on the other, or sandstone and clay may be opposite. One vein throws the strata down 25 fathoms (150 feet). The lead miner obtains all his treasures in those very dislocations which interrupt coal workings, and are by coal miners called faults and troubles.
Old miners have distinguished the lead veins by the names of rake, pipe, and flat veins. Rake veins are the most common in Cumberland, &c. They are generally narrower in the sandstone that covers the limestone than in the calcareous and siliceous beds. In the rich vein of Hudgill Burn the thickness is 17 feet in the Great Limestone, while it does not exceed 3 feet in the overlying sandstone. The influence exercised on metallic veins by the inclosing rock has been mentioned before, and is confirmed by wide observation in other countries, particularly in the veins of Kongsberg in Norway. Perhaps, however, the phenomena are nowhere more satisfactorily displayed than in the north of England. The mining districts consist of shales, grits, and limestones, traversed by east and west, and north and south veins, which variously dislocate the strata. In the course of these unequal dislocations, coupled with unequal thicknesses of strata, various oppositions of the argillaceous, arenaceous, and calcareous rocks take place. It is chiefly in the limestone that the veins are productive, although the fissures traverse a vast thickness of overlying strata, as shales, grits, and coal. In a series of limestones, gritstones, and shales, adjoining or forming the margin of a vein, it happens that when inclosed between cheeks or walls which are both argillaceous, the vein will be unproductive and generally nipped or reduced in width. With argillaceous beds on one side, and gritstone or limestone on the other, the same effects appear, but in an inferior degree. Gritstone opposing gritstone yields irregular results, according to the mass or quality of the gritstone; so that in several districts (as Allenheads, Grassington, &c.) much lead ore has been found in such situations. But when limestone is opposite to limestone the vein is almost always most productive. Of the stratum called the Great Limestone, and its metallic productivity, we have already written. The rake vein is by some divided into two kinds, one of which, the slip vein, prevails most commonly in Alston Moor. Pipe veins are seldom of great length, but often have considerable width. They appear to be the result of a segregation of the metallic contents of a vein into portions inclined at various angles in different veins, but nearly parallel in the same vein. The pipes or shoots are usually very productive for a long course in a long vein. Flat veins seem to be expansions of the matter of the vein between the planes of the strata, and contain the same ore as the veins in their vicinity. When metalliferous, they are worked along with the adjacent rake vein, and are productive only to a certain distance from that vein, unless they become enriched by crossing a rake vein. The rake veins are the most productive of all in the north; and observations made in Derbyshire point to the conclusion that nearly the same conditions govern the lead veins in that county. An opinion prevails in the north that the greater number of lead veins are at right angles to the plane of stratification, and this opinion is not without foundation.
The numbers of males employed in lead mining in the northern counties of England are as follows:—In Durham, 2628; in Northumberland, 1070; in Cumberland, 1840; in Westmoreland, 317; in all, 5855.
Considerable numbers of young persons are employed at the surface works in dressing the ores. This process consists in—1. The sorting and cleansing of the ores; 2. The grinding; 3. The washing, properly so called. These operations are much alike in the English lead districts, but they are most perfect in the north.
The lead and argentiferous lead districts of South Wales Welsh lead lie chiefly along the shores of Cardigan Bay. The district containing the known argentiferous and lead ores stretches from about the centre of Carmarthenshire on the south, through Cardiganshire, and some distance into Montgomeryshire, on the north, and from about 5 to 20 miles from the sea towards the interior, or from W. to E. The most productive portion of the country as regards silver lies about 7 miles to the eastward of Aberystwith, perhaps the most beautiful of the Welsh watering-places. This contains the great mines Cwm Symlog, Goginan, Daren, Cwm Sebon, Bwlch Consols, &c. The district in which these mines are situated abounds in majestic scenery; the great mountainous region, commencing at Snowdon on the northward, passes southward through its centre, Plynlimon being in the midst of the metalliferous deposits, and rising at 17 miles from the sea to the height of 3300 feet above its waters. The views on the rivers are amongst the most beautiful in the British Isles, and the well-known Devil's Bridge overspreads a cataract on one of the streams, and falls over a ledge of rocks from a height of 480 feet into the bed of the Rheidol.
The present annual produce of these mines must not be taken as showing the produce in past years, for some of the mines formerly yielded immense profits. The lode in Esqair-y-Mwyn Mine is said to have been filled with lead for 30 feet wide, nearly solid; and although a royalty of 1.3 per ton was paid to Earl Powis, it is not improbable that the mine has returned L600,000 worth of ore. Of the other more profitable mines, it is estimated that Cwm Ystwith has yielded L500,000, Grogwinion L250,000, and Logylas L200,000 worth of ore. In the main silverlead districts of Cardiganshire, amongst the mines of which are Goginan, Bwlch Consols, Daren, &c., the total produce has been estimated to have been L1,500,000 for lead, and L1,000,000 sterling for silver. Yet the whole of these mines have been worked to but a comparatively shallow depth.
The group of mines adjacent to Talbot, 7 miles north of Aberystwith, includes Esqair-frith, formerly called the "Welsh Potosi," and famous for having yielded immense masses of ore. The history connected with these mines is very remarkable, but we can only briefly notice it. The estimate of Mr Waller sounds extravagant to us at this day; but it is believed that he proposed to realize a profit of Mines and Mining.
L75,000 a-year from these mines alone. It is reported that Sir Carberry Pryse (ancestor of the Gogerddan house) refused L75,000 for a moiety of them. It may be presumed that the whole of the mines in this part have actually yielded not less than ores worth one million sterling. It is very curious, when we are made acquainted with such facts, to read this passage in Cicero's Letters (Epist. ad At.) written almost immediately after the disembarkation of Caesar's troops on our island:—"One thing we are already certain of, that there is not a grain-weight of silver in that island, nor the least prospect of plunder, but from the slaves that may be brought away."
The metalliferous district of Cardiganshire and Montgomeryshire is formed exclusively of clay-slates and gritstones underlying the lowest beds in the Silurian system of Murchison. Large portions of this principal district are as yet not known to contain mineral veins; and the intermediate parts which are the most noted for their productiveness, are defined by certain limits intimately related to the lithological character of the rocks. The prevailing strike of the beds is from N. by E. and S. by W., to N.N.E. and S.S.W.; and in the same direction bands of various width may be traced in which a number of the most successful mines have been worked. There are several anomalous features in this district, if compared with other mining districts. The presence of ore cannot be directly ascribed to the proximity of granites or porphyries, since this is the only large portion of the slaty rocks of Wales in which not a vestige of any rock of igneous origin is met with. The various directions of the lodes gives no clue to the determination of their relative age.
The band known about two centuries ago as the "Welsh Potosi," from the enormous returns it yielded to Middleton (afterwards Sir Hugh Middleton), is at the present day distinguished by the mines of Goginan, Cwm Sebon, Cwm Symlog, Daren, &c. The slaty rock there assumes a paler tint, inclining to a bluish or greenish gray, and exhibiting on the whole a more massive bedding, in consequence of which it would appear that the mineral veins increase in width, expanding in some cases to upwards of 20 feet. This ore is generally argentiferous, sometimes to the amount of 38 oz. in the ton. Several facts have been observed with reference to the ore-bearing portions of the lodes, which are in perfect accordance with the experience of other districts. When the lodes approach each other under a small angle, the junction is nearly always marked by a larger deposit of ore. The lead veins of this part of Wales differ from those of Cornwall in one point, upon which all the miners are agreed,—viz., that when they pass from a harder to a softer rock, their mineral contents decrease. In Cornwall, however, we observe, that at the exceedingly productive mine of East Huel Rose, not only is the kilias or clay-slate very soft, but the lode itself, including its saccharoid quartz, is in so disintegrated a condition that a blow with the pick will often cause it to run down like a quantity of sand or mud.
There are about 120 named lead lodes in Cardiganshire, some worked, and others not. The most productive of those at present in work are, first, those named Pen-y-Gist South Lode, Logauas, &c., forming the Lishurne Mines. From these the lead ore returns in 1845 were 2492 tons; in 1846, 1724 tons; in 1853, 2752 tons; in 1854, 2595 tons. 500 persons were employed there. Secondly, the next most productive mines are Goginan North and South Lodes,—the lead ore returns being 1768 tons in 1845, and 1627 tons in 1846. The number of persons then employed was 400. The above mines were very far more productive than the remainder in the county. In Montgomeryshire we find 38 named lodes, of which the principal are,—that named Llechwydd-ddu, a rich and regularly-worked vein; and Escairgaled, which averages 16 feet wide, and has been productive in former times. Both these united yielded in 1845 586 tons of lead ore, and in 1846, 557 tons of lead ore; the number of persons employed being 200. In 1854 we find the most productive mine in this county to be Machynlleth, which, including Delife, yielded 637 tons of ore, affording 470 tons of lead.
Many considerations tend to encourage the development of the mineral resources of this district: the great number of lodes lying idle, or only in some cases tried to a small depth; the probability of the existence of many more, in consideration of the difficulty of discovering them from the surface; the facility of drainage; and the fact of the resumption of the two most profitable mines from very fortuitous circumstances—the very profitable mines of Logauas and Goginan. Logauas had been erroneously worked, and the true lode was missed, until the present holders, after making an accurate survey, altered the drivings, and shortly discovered, not only the lode, but a rich bunch of ore, parallel to which their predecessors had been toiling for many a fathom through barren rock at the distance of only a few feet. The mine has ever since continued to yield several thousand pounds of profit yearly. Still more hopeless did the condition of Goginan appear to be when commenced; yet the mine has since produced upwards of 1500 tons of silver-lead ore yearly. The mode of working these veins is very similar to that adopted in our southern counties, and most of the mining captains are Cornishmen.
In Derbyshire the metalliferous limestone occupies a Derbyshire length of about 25 miles from north-west to south-east, with shire, a very variable breadth, which, however, towards the south, amounts to 25 miles. Castleton to the north, Buxton to the north-west, and Matlock to the south-east, lie nearly upon its limits. This limestone district is surrounded nearly on all sides by the millstone grit which covers it, and which is in its turn covered by the coal strata. The nature of the rocks beneath the limestone is not well known. In Cumberland the metalliferous limestone includes a bed of igneous rock, called trap (from the Swedish word for stair) by mineralogists, but locally whinside. Igneous rock is much more abundant in Derbyshire, where it is termed toadstone (probably from the German todstein, dead rock), and it is there thrice interposed between the beds of limestone. These two rocks of themselves constitute the whole mineral mass through a thickness of about 550 yards, measuring from the millstone grit—only in the upper portion—that is, near the millstone grit—there is a considerable thickness of argillaceous schists. The toadstone is of various thicknesses and colours, and is sometimes very porous, and presents the appearance of scoria or volcanic lava. It is the miner's dread, as it is thought to cut off the vein of ore. On Tideswell Moor, however, where toadstone intersected the vein that was worked in the incumbent limestone, it at once cut off the vein; but when the miners cut through the toadstone, they met with the limestone underneath, and the continuation of the lost vein. At Black Hillock Mine, where the vein was cut off by toadstone, they sank for 600 feet in its mass, and yet could not get through it; while at a distance on either side miners got through the toadstone in a few fathoms. It appears that though the vein may be retraced on the other side of the toadstone in the limestone again, yet it is generally very thin, and sometimes extremely poor.
The veins in this district are of three descriptions:—1st. The pipe-vein, which lies between two rocks of limestone extending regularly above and below. It consists of several lines or branches running nearly parallel to each other; and although they sometimes deviate from that course, they generally return after a short distance. The branches communicate with each other by means of slender threads or leadings. Sometimes the surrounding rock is penetrated by these transverse threads, and by pursuing the thin veins Mines and a new repository of metal may be discovered. 2d. Rake Mining, veins traversing the strata; and, 3d. Flat veins, forming beds along with the horizontal strata, and generally lying near the surface. A variety of the ore, termed by the miners slickensides, abounds in some parts, and forms the sides of cavities. Some fabulous tales of its explosive violence are narrated in the district. It presents a smooth surface with a bright metallic lustre. The blocks of lead bearing Latin inscriptions, which have been found here, have led some to think that the mines of this county were wrought in the time of the Romans.
In the table of lead-ore returns for 1854 it will be seen that those of Flintshire are nearly equal to those of Cardiganshire. The most productive mines in Flintshire are those called Talargoch, which in 1854 yielded of lead ore 1910 tons; and these afforded 1490 tons of lead, from which was extracted 10,430 ounces of silver. The next richest mine is Maes-y-safn, yielding 1423 tons of ore, equalling 1117 tons of lead and 3071 ounces of silver.
The most important items of returns from other lead-mining districts for 1854 are as follows—Derbyshire yielded 7554 tons of lead ore, affording 4508 tons 15 cwt. of lead. The largest mines in Yorkshire are Swaledale and Arden-dale, yielding 4817 tons of ore, or 3276 tons of lead; Grassington is the second in yield. In Scotland the Wanlockhead Mines yielded 795 tons of ore, or 596 tons of lead. In Ireland the Newtownards Mine afforded 1379 tons of ore, and 1084 tons of lead; the Luganure Mines in Wicklow yielding 1095 tons of ore, and 710 tons of lead and 4970 ounces of silver. In the Isle of Man the principal mines, the Foxdale, yielded 1900 tons of ore, or 1449 tons of lead, the proportion of silver being 19,926 ounces.
Iron.
For information respecting iron, its localities, &c., see the article Iron.
Zinc.
Our islands produce considerable quantities of zinc. There were obtained from the mines of Cornwall, Wales, Cumberland, and the Isle of Man, during the year 1855, not less than 5000 tons of zinc ore, in the form of sulphuret of zinc or black-jack, and calamine, a carbonate of zinc. The estimated value of this product was at least L17,000. As the price for zinc is advancing, and as it is now selling at prices varying from L2, 10s. to L3 per ton, we may expect a new business for our zinc mines. The great supply of zinc for this country has hitherto been derived from the works of the Vieille Montagne Company. Our imports in the last five recent years have been as annexed:
| Years | Zinc | Oulds of Zinc | |-------|------|--------------| | 1850 | 18,623 | 170 16 | | 1851 | 22,986 | 495 9 | | 1852 | 18,505 | 787 9 | | 1853 | 23,418 | 342 0 | | 1854 | 19,483 | 336 0 |
Calamine is very abundant in England, as in the Mendip Hills and parts of Somersetshire; at Holywell, Flintshire; at Castleton, Derbyshire, and in Cumberland. In 1854 the English zinc mines produced 4531 tons 3 cwt. of sulphuret of zinc, and 280 tons 11 cwt. of calamine. The value of the zinc smelted in England in 1854 was about L16,500.
Cornwall and Devonshire yield annually not less than 1500 tons of arsenic, a considerable proportion of which is employed to give the required whiteness to copper in our white-metal manufactures, and hardness to steel; and a large quantity is exported to Russia and other places, where it is used in dressing furs and skins.
We have also in our country antimony, nickel, cobalt, manganese, and some other metals, which are of use in the Antimony, arts. Cornwall formerly supplied antimony to the type-founder, but now we import nearly all the antimony we use. Antimony is found at Rosenau in Hungary; in Saxony and the Harz; in Spain, Tuscany, France, Siberia, Mexico, and the Indian Archipelago. The St Austell Consols Mine sold two years ago about 150 tons of nickel and cobalt; and the mines of the Duke of Argyle in Scotland produced about 300 tons, averaging about 6 per cent. for nickel. All the nickel which our white-metal manufacture requires is supplied from Norway and Germany. Cobalt is of interest to us as being the basis of the blue colour in our earthenware, &c., and nickel as an essential ingredient in various metallic alloys, such as alba and German silver. The two metals are often associated in the same mass. A specimen of ore found near Keswick, Cumberland, contained from 2 to 3 per cent. of cobalt, but no nickel. The ores found in Cornwall include both nickel and cobalt; but as they seldom contain more than from 2 to 7 per cent. of available metallic matter, while the ores on the Continent frequently contain from 12 to 15 per cent., the process which may answer in the reduction of the richer ores may prove too costly in the poorer ones. The Swedish method has been tried with the Cornish ores, and failed.
This metal, used as a glaze or pigment by potters, &c., Manganese, occurs native in the Hartz Mountains, in Piedmont, in the Mendip Hills, Somerset, and in the counties of Devon and Aberdeen. It has been recently found that a certain proportion of this metal, added to steel manufactured from British iron, produces a cast-steel nearly equal to that obtained from Swedish iron. Great quantities of the peroxide have been found near Tavistock in Devonshire and Launceston in Cornwall.
When sulphur was high-priced, considerable quantities Sulphur were manufactured from our iron pyrites; but its present from iron comparative cheapness has greatly reduced the demand for Pyrites, our own sulphur. Some, however, being still employed in our chemical works, it is produced from a few mines, chiefly from the Irish. Since 1839 the mines of Wicklow have sold, in fifteen years, 338,368 tons; the mines of Arklow, 606,972 tons; collectively, 945,340 tons. In the last year of the fifteen, viz., 1854, the quantities were,—Wicklow, 34,000 tons; Arklow, 90,000 tons; collectively, 124,000 tons. Cumberland and Westmoreland sold in that year 2400 tons. The Wicklow and Arklow mines, which produce the iron pyrites, all contain the same "sulphur course," which traverses them in a north-eastern and south-western direction. The iron pyrites consists, in 100 parts, of iron 46·67, sulphur 53·33.
Rock-salt is mined in some countries, and especially at Wielizka, near Cracow, in Poland (in the Cretaceous formation), where the excavations are of vast extent, and have been continued, it is said, from the year 1251, extending more than a league from east to west. The salt is of an iron-gray colour, in which are found rocks of a pure white. The annual product is reported to be about 2,000,000 cwt.
The great beds of rock-salt in the New Red Sandstone of Salt-Cheshire, in our own country, are known to extend one mile and a half north-east and south-west, and to be upwards of three quarters of a mile wide. There are two beds lying one over another, and at Northwich at least 60 feet in thickness. The top of the lower bed is about 220 feet from the surface; and no bottom has been found. The salt is mostly of a reddish hue, and is so hard that blasting by gunpowder is often necessary for its extraction.
The brine springs do not fall within the description of mines. A remarkable deposit of rock-salt has recently been discovered on the Marquis of Downshire's property at Car- Mines and rickergus, about 8 miles from Belfast, Ireland. The discovery was made in searching for coal, and at a depth of about 550 feet from the surface. It is comprised in a series of strata lying contiguous to each other, and the aggregate thickness is about 100 feet. The quality is said to be superior to the Cheshire rock-salt. Hitherto no springs have been discovered. The low price of coals in Cheshire will always be in favour of the manufactures there. From all these sources the British and Irish production of salt in 1854 has been nearly as follows:
| From Cheshire about | 850,000 | |---------------------|---------| | Worcestershire about | 100,000 | | From vicinity of Belfast | 950,000 | | Total | 965,000 |
**MANAGEMENT AND FINANCE OF MINES.**
Many of the foreign mines are under the control and management of the respective governments. This is not the case with British mines, some of which belong to private individuals (as the lead mines of Mr Beaumont), some to institutions (as the Greenwich Hospital Lead Mines), and many to public and private companies.
When a company undertakes to work a mine, the lord of the land must be arranged with, and he grants a lease (sett is the mining term) upon certain terms, and demands a rent (royalty) either in ores or money. A ratio of one-fifteenth may represent the lord's average dues. Mines are worked by a greater or less number of adventurers or shareholders, either on what is termed the "cost-book system," or under joint-stock laws.
The cost-book system is very peculiar, and differs mainly from that of joint-stock companies in the control directly exercised by the whole body of the shareholders over the management of the concern. They appoint a purser, who acts as the financial servant of all, and renders an account to the shareholders at their frequent meetings. There are many advantages in this system; but legal questions and complications may arise which are difficult to decide. Many of its customs or usages are still sub judice.
Coal mines alone are under government inspection, and that exclusively with reference to accidents, their causes, and preventives. The numbers of shareholders of which the associations for working mines consist are very various; but they are more than in ordinary trading partnerships, on account of the risks and expenses of mining. In the old adventures in Cornwall the number of shares in each mine was commonly either 64 or 128. It is now desired by many to increase the number of adventurers in these concerns. If the mine be a scrip concern, there are directors, &c. In Cornwall the mining agents are termed captains; and these are divided into "grass-captains" (at the surface), and "underground captains." The purser is the chief financial and managing officer. (Cornwall; its Mines and Miners, pp. 136, &c.)
The amount invested in British mining in 1852 was about five and a quarter millions, and these investments yielded dividends of L1,409,060. Of these, mines representing L2,345,624 produced something more or less; and mines representing L1,476,666 produced nothing. Of the former class, mines representing L498,196 produced dividends of L253,057, or on the average 50 per cent. The amount of dividends paid on mining in the first nine months of 1856 may be thus classified:
| English mines | L288,889 | |---------------|----------| | Irish | 17,970 | | Welsh | 15,485 | | Isle of Man | 11,240 | | | L333,564 |
From this statement an idea may be formed of the magnitude of business in British mining companies. There is a Mining Exchange in London.
Mining schools have long been established upon the continent of Europe. The most celebrated in Germany are those of Freiberg in Saxony, and Clausthal in the Hartz. Schemnitz in Hungary has a good mining academy, founded about 1760; France has its Mining School; and generally the foreign mining districts are well provided with scientific instruction. In England there has been a lamentable deficiency of mining schools. However, the Government School of Mines was opened in London on 6th November 1851, in connection with the Museum of Practical Geology. It is a well-provided institution, having able professors, a fine museum, many models, and a good library. A mining school has been established, after many difficulties, in Truro, Cornwall, and one smaller in Bristol.
**GENERAL VIEW OF THE MINERAL WEALTH AND PRODUCE OF THE PRINCIPAL COUNTRIES OF EUROPE.**
Great Britain is the most favoured country in the world for the development of mineral industry, as well as for its mineral possessions. Fuel, the indispensable agent in the treatment of metalliferous ores, and the most powerful element in the production of motive force, is distributed, though unequally, throughout the three countries of England, Scotland, and Ireland. The coal formation in these three divisions of the British Empire occupies rich and widely-spread basins, several of which (especially those of Newcastle-on-Tyne, Scotland, and Wales), being situated near to the sea, which surrounds the whole country, are enabled to export the coal to those places in which the metalliferous ores exist in abundance; but in some districts (as in Cornwall), the absence of fuel renders the work costly and difficult. The ores of iron, abundantly distributed in several of the coal basins, add greatly to their value. Each coal basin so situated has become the centre of a metal-working district, where numerous works produce iron at a price so comparatively moderate, that no nation has as yet been able to compete with us with any great success. The insular position of Great Britain allows the coal to be conveyed at a minimum cost wherever it is wanted, and is equally important in permitting iron or other metals to be shipped to any part of the world. Hence the importance of these particulars of situation, &c., is strongly shown when we state, that while England is thus enabled to supply her iron at a price which ejects all rivals from the market,—and while she exports annually upwards of 800,000 tons (her mean annual importation during the five years ending 1852 being 32,197 tons), and could supply the whole European continent,—yet the quality of her iron is considered by foreigners to be but middling, and it is not applicable to the purposes for which she imports the finer iron; while for the manufacture of steel she imports from Sweden and Russia. The manufacture of steel is very backward in Russia. Asia and European Turkey take more than two-fifths of the Russian exported iron, England and the United States nearly two-fifths, and other countries somewhat less than a fifth.
From time to time a few conjectural estimates have been formed of the value of the produce of the British mines. Dr Buckland, in his address to the Geological Society in 1840, remarked,—"The average value of the annual produce of the mines of the British Islands amounts to the enormous sum of L20,000,000, of which about L8,000,000 arise from iron, and L9,000,000 from coal." Sir Henry de la Beche in 1851 stated, that "the raw mineral produce of Great Britain and Ireland is valued at L24,000,000 per annum, or about four-ninths of that of all Europe, including these islands; the coal being estimated at the pit's mouth, the iron in the pig, and so on." The following is Mr Hunt's estimate of the annual value of our produce of metals and minerals for two recent years, taken from the Government Geological Survey:
| Value of British Produce for | |-----------------------------| | 1853 | 1854 | | Iron (pig) | L10,000,000 | L9,500,000 | | Copper | 1,500,000 | 1,229,807 | | Lead | 1,000,000 | 1,472,115 | | Tin | 400,000 | 690,000 | | Silver | 210,000 | 192,500 | | Zinc | 10,000 | 16,500 | | Coal at pit's mouth | 11,000,000 | 14,975,000 | | Other minerals, as Nickel, Arsenic, Sulphur | 400,000 | 500,000 | | **Total** | **L24,320,000** | **L28,575,922** |
The number of persons employed in British mining is as follows:
| Men and Women of all ages | |---------------------------| | Coal | 219,995 | | Iron | 26,106 | | Copper | 21,169 | | Tin | 14,764 | | Lead | 21,769 | | Zinc, &c. | 174 | | **Total** | **303,977** |
An analysis of this number affords the following particulars:
- Males under 20 years of age: 86,647 - Do, 20 years old and upwards: 208,520 - Total Males: 295,167
- Females under 20 years of age: 4,994 - Do, 20 years old and upwards: 3,816 - Total Females: 8,810
- Total Males and Females: 303,977
According to the estimates of Tegoborski (Commentaries on the Productive Forces of Russia, by M. L. de Tegoborski, Privy Councillor, &c. of the Russian Empire, Svo, London 1855, vol. i., p. 213), the latest and most reliable Russian authority, the principal products of the Russian mines of gold, silver, platina, iron, copper, lead, zinc, coal, and salt, together represent a value of L5,460,000 sterling, of which more than 55 per cent. is gold alone. This estimate excludes the accessory products of the mines,—granite, malachite, gems and precious stones, &c., found in mountains of Siberia. With the addition of these secondary articles of the mines and quarries, the author carries the gross value of the whole productions of the Russian mineral kingdom to L6,333,333 sterling.
In Austria, the whole products of mines, salt excepted, on an average of the years 1841–1844 inclusive, represented a value of 22,102,000 florins. Adding the gross value of salt, at 1 florin per quintal, the gross total product of the mines will be 27,602,000 florins, equal to L2,750,000 sterling. Taking into account the progress of production during preceding years, the present total Austrian production is estimated at about L3,166,666.
In Prussia, according to statistical information published in the Berlin newspapers, the total produce of the mines amounted in 1848 to nearly L5,000,000 sterling.
In France, according to M. Schnitzler's statistics, founded on official returns, the total produce of the mines represented in 1843 a value of L16,640,000, and according to the progress of production assigned by this author, it may now be carried to about L16,800,000 sterling; but in the French estimates the produce of quarries and peat bogs, to the amount of L1,600,000, is included. It would appear, too, that M. Schnitzler's rates of valuation are much higher than those of Tegoborski.
Thus an approximative comparison may be instituted, from which it would follow that the produce of mines in Russia exceeds that of the mines of Austria in the proportion of 2 to 1; exceeds Prussia by more than a third; but attains only two-fifths of the mining produce of France, and is therefore, of course, greatly inferior to that of Great Britain.
An approximative attempt at exhibiting a complete view of the metallic produce of the world for 1854 has been made in the subjoined table by Mr Whitney, an American:
### Table of Metallic Produce for 1854
| Countries | GeM. | Silver | Mercury | Tin | Copper | Zinc | Lead | Iron | |-----------|------|--------|---------|-----|--------|------|------|------| | Russia | 60,000 | 58,000 | 6,500 | 4,000 | 800 | 200,000 | | Sweden | 2 | 3,500 | | | | 200 | 150,000 | | Norway | | 17,000 | | | | | 5,000 | | Great Britain | 100 | 70,000 | 7,000 | 14,500 | 1,000 | 61,000 | 3,000,000 | | Belgium | | | | | | 16,000 | 1,000 | 300,000 | | Prussia | | 30,000 | | | | 33,000 | 8,000 | 150,000 | | Hartz | 6 | 30,000 | | | | 150 | 10 | 5,000 | | Saxony | | 60,000 | | | | 100 | 50 | 2,000 | 7,000 | | Rest of Germany | | 3,000 | | | | | | 1,000 | 100,000 | | Austria | 5,700 | 90,000 | 500,000 | 50 | 3,500 | 1,500 | 7,000 | 225,000 | | Switzerland | | | | | | | | 15,000 | | France | | 5,000 | | | | 1,500 | | 600,000 | | Spain | 42 | 125,000| 2,500,000| 10 | 500 | | 30,000 | 40,000 | | Italy | | | | | | 250 | | 500 | | Africa | 4,000 | | | | | 600 | | | | East Indies and So. Asia | 25,000 | | | | | 5,000 | 3,000 | | Australia, Oceania | 150,000 | 8,000 | | | | 3,500 | | Chile | 1,000 | 250,000| | | | 14,000 | | Bolivia | 1,200 | 130,000| | | | | | | Peru | 1,900 | 30,000 | 200,000 | 1,500 | | | | | Ecuador and N. Granada | 15,000 | 130,000| | | | 1,500 | | Brazil | 6,000 | 700 | | | | | | | Mexico | 10,000| 1,750,000| | | | | | | Cuba | | | | | | 2,000 | | | United States (incl. California) | 200,000 | 22,000 | 1,000,000| 3,500 | 5,000 | 15,000 | 1,000,000 |
Total | 479,950 | 2,812,200 | 4,200,000 | 13,660 | 56,550 | 60,550 | 133,000 | 5,792,000 | The following table of the values of the metallic produce of different countries, showing the ratio of their production as compared with that of the United States and that of Great Britain, has also been compiled by Mr Whitney:
| Countries | Value of metals produced in pounds sterling | Ratio of production to that of United States | Ratio of production to that of Great Britain | |----------------------------|---------------------------------------------|---------------------------------------------|---------------------------------------------| | United States | L16,630,625 | 1:00 | 5:6 | | Great Britain | 20,035,376 | 1:205 | 1 | | Australia | 8,214,167 | 4:94 | 5:12 | | Mexico | 6,350,990 | 3:82 | 1:3 | | Russian Empire | 5,253,333 | 3:16 | 4:15 | | France | 3,177,694 | 1:91 | 1:6 | | Chili | 2,738,233 | 1:65 | 2:15 | | Rest of South America | 3,370,000 | 2:03 | 1:6 | | Austrian Empire | 355,558 | 1:47 | 1:8 | | Prussia | L4,100,000 | 2:21 | 1:10 | | Belgium | 1,953,125 | 1:18 | 1:10 | | Spain | 1,670,087 | 1:00 | 1:02 | | Sweden and Norway | 1,137,687 | 0:68 | 1:17 | | Saxony | 303,125 | 0:18 | 1:67 | | Harz District | 239,081 | 0:14 | 1:86 | | Italy | 173,437 | 10 | 1:120 | | Switzerland | 78,125 | 0:05 | 1:240 |
With reference to Great Britain, mining operations are carried on to a greater or less extent in 21 English counties and the Isle of Man, in 12 Welsh counties, and in 17 counties in Scotland. Coal and iron, of some varieties, are found in greater or less proportions in nearly all the counties of England. In examining the counties in Wales and Scotland, we find a similar wide diffusion of coal and iron, and in Wales of lead. In Ireland we observe a wide diffusion of coal and lead, and argentiferous lead. Other minerals are far more rare.
(J.R.L.)