The Subterranean World

by G. Hartwig

Mercury does not rank among those metals which are copiously disseminated over the surface of the earth. Considerable deposits or veins of even its commonest and most abundant ores (red cinnabar; hepatic cinnabar) are confined to a few spots, and all Europe possesses but two important quicksilver mines—at Almaden in Spain, and Idria in Carniola.

The Sierra Morena or the Black Mountains in the Iberian Peninsula, so well known as the scene of the exploits of Don Quixote, are no less renowned in the mining world for their subterranean riches, among which the famous quicksilver mines of Almaden del Azogue hold a conspicuous rank. This small town of about 10,000 inhabitants is situated on the northern border of the above-mentioned mountain chain, at the south-western extremity of the province of New Castile, and, unlike most other Spanish cities, affords the pleasing sight of well-built houses and clean and regular streets. As is generally the case in mining districts, the neighbourhood is sterile, but picturesque, and from the neighbouring mountains magnificent prospects open on every side.

The mines of Almaden, after having been the property of the religious knights of Calatrava, who had assisted in expelling the Moors, were farmed off to the Fuggers, the celebrated merchant princes of Augsburg, whose descendants still rank among the high aristocracy of Germany. Afterwards, from the date of 1645 till the present time, they have either been worked on Government account or farmed off to private companies. A visit to these celebrated mines is highly interesting. A spacious tunnel or gallery, completely walled with solid masonry, leads into the bosom of the mountain and branches out at its extremity into several galleries hewn in the slate which forms the matrix of the vein. One of these galleries conducts to the Boveda de Santa Clara, a vast circular hall in which formerly stood a horse-gin, for raising the ore to the surface. At present, however, this work is performed through a shaft which descends to the lowest level of the mine. From another gallery convenient stairs lead down to the first working level of the mine, and thence short ladders to the deeper stories. The shafts are wide, the galleries high enough to allow one to walk upright through them. The upper stories are almost thoroughly dry, the lower ones humid; the water, however, is easily removed by hand-pumps, which raise it from story to story into a large subterranean reservoir, emptied once a week by a steam-engine of fifty-four horse-power. The veins are so extremely rich that, though they have been worked pretty constantly during so many centuries, the mines have hardly reached the depth of 1,140 feet. The lode actually under exploration is from fourteen to sixteen yards thick, and it becomes thicker still at the crossing of the veins. Its present annual produce amounts to about 80,000 cwt. of pure mercury. The ore presents a beautiful sight in the galleries where it is worked, on account of the dark red glittering colour of the cinnabar, which is sometimes earthy and sometimes forms compact crystalline masses, or fine crystals mixed with calcareous spar. Often when a hewer detaches a block of ore with his pickaxe, quicksilver masses of the size of a pigeon’s egg roll from a crevice in which they were lodged, and, leaping along the floor, divide into thousands of small drops. This, however, is no loss, for all the rubbish which accumulates in the galleries is carefully collected.

The ores are treated in thirteen double distillatory furnaces, called alodels, and yield only ten per cent. upon an average. But the analysis of the ores leaves no doubt that the barbarous apparatus employed in its sublimation causes a loss of nearly one-half of the quicksilver, which is dispersed in the air, to the great injury of the workmen’s health. This apparatus has remained without any material change for the better since the days of the Moorish dominion in Spain. The furnaces are heated with brushwood, particularly with the resinous branches of the Cistus ladaniferus, which grows over the greatest part of the surrounding mountains. This dark evergreen shrub often extends over many miles of ground, and when in flower covers the hills with a beautiful snow-white carpet.

Formerly only criminals condemned to hard labour for life were employed to work in the mines of Almaden. At sunrise they were conducted from a prison, which still exists, through a subterranean passage into the mines, where they were obliged to toil till evening, when they were led back again to their dungeons, so that they never saw the light of day. After a few years these poor wretches generally died from inhaling the poisonous vapours of the mercury. Reduced to despair, they set fire, at the beginning of the last century, to the galleries, which were then constructed of wood, and thus rendered the mining operations impossible for many years. Since then only free miners are employed, who are well paid, and not allowed to work longer than six hours a day. Most of them, however, die at an early age, between thirty and forty, and those who live longer are affected by a spasmodic trembling, so as to be unable to keep a limb quiet.

After the mines of Almaden those of Idria in Carniola are the richest in Europe. This neat little town lies in one of the largest and most picturesqe basins of the Julian Alps. The gigantic and naked rock walls which inclose the sequestered valley are only partially decked along their summits with clumps of firs; but lower down the slopes are covered with beautiful meadows and forests, and here and there on the projecting spurs of the mountains stand picturesque chapels, which serve to heighten the beauties of the magnificent panorama.

Chance—to which man owes so much both of good and evil—also led to the discovery of the subterranean treasures of Idria. In the year 1497 a peasant found, in a tub which he had placed under a brook, some drops of a heavy liquid shining like silver. Although quite ignorant of the value of his discovery, he still was cunning enough to carry them to a goldsmith without mentioning the place where he had found them. At length a man named Anderlein, having promised him a handsome reward, became master of the secret, and associating himself with several wealthy persons, began to work the mine. After several years the property passed into the hands of a company of goldsmiths of Salzburg and Augsburg, which derived such profits from the mine as to excite the greed of the neighbouring Venetians, who in the year 1510 forcibly drove away the Germans, but were soon after expelled by the Emperor Maximilian, who, as soon as he heard of this insolent attack, sent some troops into the forest of Idria and restored it to its rightful owners. In 1578 the mine was incorporated among the domains of the State, and began to be worked with greater regularity.

The entrance lies to the south of the town, on the slope of a small hill projecting from the circular zone of mountains which gird the basin. The visitor may either descend, in less than five minutes, to the bottom of the pit, through a perpendicular shaft, in one of the large tubs which serve to raise the ore, or he may make use of convenient stairs. Here and there are landing-places, whence galleries lead to the various fields or stories of the mine, the lowest of which is 145 fathoms under ground. The vein, however, descends much further, to an unknown depth, and its horizontal extent has likewise not yet been measured.

As the limestone in which the ores are imbedded does not form a solid compact mass, but is of a loose nature, most of the galleries had, from the very beginning of the mining operations, to be artificially propped. Until the end of the last century wooden beams were chiefly used for this purpose—a construction which frequently gave rise to fearful fires. Thus on March 16, 1803, the workmen saw a thick smoke issuing from several of the deepest galleries. It rose higher and higher, and spread through the upper galleries of the mine. No fire was to be seen, no sound of flames was to be heard, yet there could be no doubt that the mine was burning. Some of the workmen boldly undertook to descend to the scene of the fire, but in vain; they were obliged to flee before their enemy, for the smoke was not only dense and suffocating, but so impregnated with poisonous vapours that no living being could exist within its reach. An attempt was now made to smother the fire by shutting out the air. All the galleries were blocked as near as possible to the supposed seat of the fire, as well as the two shafts which led to the upper world. The mine remained thus closed during five weeks, but to no purpose; for when it was reopened, the fire burst forth more furiously than before. The flames now howled fearfully from the bottom of the pit, and the mercurial and sulphurous fumes which rose from it threatened instant death to anyone who should be rash enough to approach them. The director of the mine now resolved to flood the works as a last resource against the ravages of fire. A river was turned into the perpendicular shaft, and ran during two days and three nights into the pit. On the first day there was no perceptible effect, but on the second—whether it were that the vapours produced by the meeting of the antagonistic elements were striving for an outlet, or that new inflammable gases had been formed—a most terrific explosion took place, which made the whole mountain tremble as if shaken by an earthquake. The huts close to the opening of the shaft were rent to pieces, the stone houses at the foot or on the slopes of the hill fell in with a tremendous crash, and the inhabitants of Idria, fancying the day of judgment had arrived, fled in terror to the hills.

In the mine itself the explosion was afterwards found to have torn up the galleries, to have burst the vaulted roofs, and to have hurled away the stairs. But the victory was now won. The vapour gradually drew off, and after a few weeks it was possible once more to descend into the pit. Two full years, however, passed before the water was fully pumped out into the Idriza, where it poisoned all the fishes, with the exception of the eels, who, it seems, are proof against everything except roasting or boiling. Even after all the water had been removed, it was still found impossible to work in the mines, partly from the heat, but chiefly on account of the venomous fumes, which soon produced all the symptoms of mercurial disease.