In the manufacture of glass and crystal it plays an important part, as it forms one of the chief ingredients of flint-glass and crown-glass, of which, as is well known, the achromatic lenses are made which have so wonderfully improved the distinctness of our telescopes. United with tin it forms an alloy which is more fusible than either metal alone, and which is consequently used as a solder by the plumbers, while with antimony it combines into a hard mass which serves to make letters for the printing-press. All these various uses absorb immense quantities of lead, and render it one of the most valuable products of the subterranean world.
Among the lead mines of Europe we find the first rank occupied by those of Spain, which in 1863 furnished the enormous mass of 309,940 tons of galena. The principal mines are situated in Guipuzcoa, Catalonia, Arragon, the Sierra Morena, and, above all, in the mountain chain of the Alpujarras, where the rocks of the Sierra Gador are everywhere traversed by veins of galena. The production of North Germany is also very considerable. In 1865 Prussia furnished 57,808 tons of galena, and the Hanoverian Hartz Mountains, which produced 101,411 tons in 1864, and now belong to the same monarchy, have raised its previous production to a threefold amount.
The chief lead mines of England are situated near Alston Moor, where the three counties of Northumberland, Durham, and Cumberland meet together. The lofty hills of the district, bare of wood and almost wholly covered with marshy heaths, are intersected by the valleys through which run the Tyne, the Wear, and the Tees, with their numerous branches. The country, though little frequented by tourists, is wild and picturesque; but the deep gorges with which it is furrowed have more than a mere romantic interest, for they lay open to view numerous veins of ore, and direct the operations of the miner to the places where it is sufficiently abundant to reward his toil. The town of Alston, the mining centre of the district, is beautifully situated close to the river Tyne, which, about five miles above it, ascends, between lofty hills, to the foot of Cross Fell, this picturesque mountain giving a character of considerable grandeur to the surrounding scenery. The mines of the Alston Moor district produce annually about 25,000 tons of lead. The waters are drawn off by long adit levels, and the ores are dragged out by horses to the day. This region extends southward to the Yorkshire valleys of Swaledale, Arkendale, and to Grassington, where numerous lead mines are worked under very similar circumstances. The Yorkshire mines yielded in 1856 8,986 tons of lead.
Another important lead district lies in the northern part of Derbyshire, in the hilly country of the neighbourhood of the Peak, so well known and so often visited for its picturesque beauty. The mines of Derbyshire, which yield annually 5,000 tons of lead, are getting exhausted; they are very numerous, but in general inconsiderable.
Next to Alston Moor the lead mines of Flintshire and Denbighshire are the most productive, furnishing annually nearly 6,000 tons of lead. An important group of veins of lead occurs in the slaty rocks of Cardiganshire and Montgomeryshire, all of which have an E.W. direction; although so far from parallel that they often meet, and frequently form at such points of intersection ‘courses’ of ore. Some of these mines were very profitably worked in the seventeenth century, and during the last thirty years several of them have been highly productive.
There are considerable lead mines in the south of Scotland, at Wanlockhead and Leadhills in Lanarkshire; and those of Strontian, in Argyleshire, likewise deserve to be noticed. The Isle of Man has two important lead mines, the Foxdale and Laxey, the former remarkable for the great size of its main lode. The elevated tracts of Wicklow likewise contain some valuable lead mines, at Luganure and Glenmalure. In 1866 the total produce of our lead mines amounted to 91,047 tons of galena, which yielded 67,390 tons of metal.
The island of Sardinia, already renowned among the ancients for its rich lead mines, produces about 15,000 tons, or nearly as much as France, where however the extraction of galena has of late years made considerable progress.
Belgium, which in 1841 produced no more than 34 tons, raised in 1864 no less than 16,780 tons, chiefly from the mines of Bleyberg-à-Montzen, situated in the carboniferous limestone near Verviers. To render these rich deposits available, vast difficulties had to be surmounted by the united powers of enterprise, capital, and engineering skill. Rivers and brooks, diverted from their ancient course, were made to flow through new water-tight channels, and such is the amount of drainage required in that aquiferous region that engines of two thousand horse-power have to raise from a depth of 360 feet a daily quantity of 800,000 cubic feet of water.
In Greece the immense mounds of scoriæ accumulated near the ancient silver mines of Laurium, have been found to contain about ten per cent. of lead. Their total mass is estimated at no less than 3,000,000 tons, and they afford a convincing proof both of the importance of the ancient silver production of Attica, and of the imperfection of the old Athenian mining operations. A French company has lately been formed for smelting this prodigious accumulation of scoriæ, once cast aside as rubbish.
In Siberia the famous lead mines of Nertschinsk, where many an unfortunate exile is doomed to end his days, are worked merely for the silver contained in them.