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