FAHLUN, a town of Sweden, in the province of Daleearlia, is situated about 300 feet above the level of the sea, between the two lakes of Run and Warpen, in a small plain, surrounded on all sides by low hills. The town, which owes its existence to the celebrated copper mines in its neighbourhood, is very regular, and consists of several parallel streets, crossed at right angles by many others. The houses are principally built of wood and of stone, and there arc two churches in the town built with brick, and one of them roofed with copper. The following very interesting and ac curate account of the celebrated copper mine, is abridg ed from the full account given by Dr Thomson, in his recent travels in Sweden. " The mine of copper ore consisted of an immense cone of copper and iron py rites, placed with its apex downwards. It has been wrought from time immemorial, and formerly with so little care, that about 150 years ago, the whole works fell in, leaving a great hollow, still very conspicuous as we approach the mine. Two large pillars, or rather hills of quartz, however, remained unmoved amidst the ruins. They may be still seen rising through the bottom of the great excavation, formed by the trembling of the mine. For many years galleries were driven through the old works, and the ore extracted in that manner ; but now the vast heap of ruins has been wrought out, and they are obliged to go deeper for the ore which at present they extract. The mine is about 200 fathoms deep. The descent is by an easy winding staircase all the way ; so that you may descend to the bottom without any other inconvenience than the fatigue of going down so many steps. The galleries are all spacious: none less than eight feet in height, and some as high as thirty feet. There are about 600 workmen in the mine. The ore is extracted partly by the mallet, partly blasted by gun-powder. It is extremely poor, seldom yielding more than 1 per cent. of the copper.
To the eye, indeed, it has nearly the appearance of iron pyrites. This pyrites is frequently mixed with beau tiful crystals of actinolite, 'of considerable quantity, which gives it, when fresh broken, a very splendid appearance. This actinolite is likewise found in the neighbourhood in chlorite slate, crystallized in very regular four-sided prisms, about an inch in length, and having a greyish blue colour.
Whether the original great conical mass of ore con stituted a vein or not, it is impossible to say ; all means of tracing any thing respecting its situation having been long ago destroyed. But several veins filled with a similar ore still exist, and have been wrought.
The ore is drawn up the perpendicular shafts; the principal one or which is King Adolphus Frederick's shaft. All the machinery belonging to this mine is driven by water; and as far as my observations went, the whole is constructed according to very scientific and sound principles.
The whole wood-work of the mine is impregnated with sulphate of iron. The water that collects in the mine contains likewise a portion of the same salt in so lution. As this water contains likewise a little sul phate of copper, it is pumped up, and made to run slowly through a pretty long trough, containing pieces of old iron. By this contrivance, the copper is pre cipitated. It is collected occasionally, and smelted. The water thus freed from copper, though it contains sulphate of iron, is by much too weak to render it pro fitable to crystallize the salt by means of heat.
It is concentrated by a very ingenious method, bor rowed from the method used in Germany to concen trate some of their weak salt mines. The water is pumped up to the top of a pretty high wooden stage, all wrapt round with birch twigs. It is let fall upon these twigs, and trickles over them to a trough at the bottom of the stage prepared to receive it. By this contrivance, a very great surface of the liquid is ex posed to the air, which greatly facilitates its evapora tion. This process is repeated six or seven times, as the liquid moves along from one extremity of the stage to the other. By this time it is so much concentrated as not to be very far from the point of crystallization. From this stage it runs into a large vessel lined with lead, where it is sufficiently concentrated by boiling. It is then let into a number of small square wooden vessels, set beside each other in a large apartment for the purpose. Into each of these vessels a number of wooden rods fixed to a frame are dipped. Upon these rods the sulphate of iron crystallizes. The copperas thus manufactured is used in Sweden, and exported to different ports in the Baltic.