CHAP. X. the Works. sons residing in America who possess shares in this mine. The Company pay one-eighth of the whole produce to the king. In the period of its greatest prosperity, which was about the year 1651, the produce amounted to 20,000 Produce of schippunds' in a single year; but since that time it has constantly diminished, and now yields. only from three to four thousand schippunds annually. As the produce of the mine has been diminished, so also has the number of workmen been lessened: the number of the miners now does not exceed four hundred persons; and if we include all those who are employed in the foundries and other works, the number will not exceed one thousand. state of the Mine. From the description already given of the Present form of this bed of ore, as well as in surveying Fahlun the products of the works during the last century, it must be evident that the Fahlun mine. approaches to its termination. They have already reached the lowest point of the inverted cone; and have penetrated deeper than the ore, (1) The schippund of Stralsund equals twenty lispund, or 280 pounds. According to Dr. Thomson, (Trav. in Sweden, p. 221,) in the year 1600 the Mine of Fahlun yielded eight millions of pounds of copper. The same author also informs us (p. 222), that as much copper is obtained from the mines of Great Britain alone, as from all the rest of Europe. (2) See the Vignette to this Chapter. CHAP. X. under a rather ludicrous notion, founded upon some visionary speculation, that if they persevere perpendicularly from the vertex, they will at last reach the top of another conical mass of ore, situate in an opposite direction; and which gradually swelling out towards its base, instead of diminishing from it, as in the present instance, will amply repay them for all their trouble. These hopes appear to be altogether illusory. However, much remains to be done, before the mine, even in its present state, can be exhausted. In working a mass of such magnitude, quantities of ore have been left in the sides and along the cavities of the mine: much, therefore, yet remains to be removed. The only difficulty will be, how to accomplish its removal, without causing a repetition of the catastrophe which gave birth to the present crater'. During the year before our arrival, a considerable portion of one of the sides gave way, and fell down, with a prodigious noise. This accident occurred upon a Sunday, when the workmen were absent from the mine; and, providentially, no lives were lost. After a subterraneous expedition of four hours, (1) See A, of the Vignette to this Chapter. CHAP. above X. we returned again to the upper regions and to the light of the day; and were conducted, as before, to the office, where we changed our clothes. Afterwards, we went to the house of an officer who is called the Mine Mechanician, to see some drawings and plans of the works, Works We then visited the Pump-room, and saw the ground. machinery for draining the mine: it is all worked by water-wheels; yet there is no place better suited for the use of steam-engines. Mr. Gahn told us they had recently discovered a bed of pit-coal, but that they made no use of it. Formerly, when the mine was richer, they made no use of the iron pyrites, which is dug in considerable quantity; but now a work is established for roasting this mineral, and manufacturing red-ochre as a pigment. In this process, however, they are not so economical as they might be: the sulphur, which might be collected, is allowed to escape'. The process for the peroxidation of the iron is extremely simple: it is obtained from heaps of decomposed sulphurets, or, (2) Here we procured those Designs which have been engraved for this Volume. (3) Assessor Gahn has since devised a very simple apparatus for obtaining the sulphur. See Thomson's Travels in Sweden, p.219. CHAP. Vitriol Manufactory. as they are commonly called, pyrites, which have been long exposed to the action of the atmosphere. Of these, a lixivium is made; in which a yellow mud subsiding, affords the ochre, which is submitted to the action of heat in a long furnace; so contrived, as that the flame, drawn out to considerable length, may act upon the iron oxide, and thus convert it into red ochre. At some distance from the mouth of the mine, an immense apparatus, visible over all the environs of Fahlun, for the manufacture of copperas or green-vitriol (sulphate of iron), is seen making a conspicuous figure among the other prodigious works of the place. This machine was constructed by Assessor Gahn, to whom all the vitriolic water of the mine, after the precipitation of the copper, exclusively belongs. The method is said to have been originally devised in Germany, for the concentration of weak salt-brines'. The principle of it is very simple, and shall be fully explained; although similar works, and perhaps upon a larger scale, may be found in our own country. The vast profit derived from the chemical changes which the water of the mine is made to undergo, after it has been (1) See Thompson's Travels in Sweden, p. 219. X. ble form cipitated Process for drained by means of pumps from the works, has CHAP. been owing entirely to the advancement which chemistry has made of late years. First, copper Remarkais abundantly precipitated from it by means of of Preiron: and this wash-copper, as it is called, of the Copper. Fahlun mine, has an appearance so extraordinary, that when it was shewn to the late Professor Tennant, he would not credit the fact of its being merely a precipitate of the native metal by means of iron. It consists of spheroïdal particles of native copper, of such perfect forms, that they seem like so many minute beads of metal which have undergone fusion. After the copper has been thus precipitated, the water, holding sulphate of iron in solution, is conveyed to the reservoir for the manufacture of vitriol. The base of the immense apparatus used for this operation is a wooden stage or platform, shaped like the roof of a house, sloping, on either side, towards wooden troughs, like those used to catch rain-water from the houses in England. Above this platform a double wooden rack, resembling those used for drying the harvest in Norway and Sweden', is made to extend the whole length of the sloping platform; which is concentrat ing the lye. (2) See a Vignette to the preceding Volume of these Travels, p. 208. |