The iron mines of Dannemora, eleven leagues from Upsal, contain a large quantity of ice, according to a manuscript account by Mr. Over-assessor-of-the-board-of-mines Winkler:[164] Jars, however, in his _Voyages Métallurgiques_,[165] gives a full description of them without mentioning the existence of ice. He states that ice is found in the mines of Nordmarck, three leagues from Philipstadt in Wermeland, a province of Sweden: these mines are merely numerous shafts sunk in the earth, reaching to the bottom of the vein of ore, so that they are fully exposed to the light, and yet the walls of the shafts become covered with ice at the end of winter, which remains there till the middle of September. Jars believed that, if it were not for the heat caused by blasting, and by the presence of the workmen, the ice would be perennial. Humboldt[166] speaks of the ice in these mines and on the Sauberg. Reich states that ice is found in the mill-stone quarry of Nieder-Mendig, quoting Karsten's _Archiv für Bergbau_.[167] The ice is found in the hottest days of summer, although the interior of the quarry is connected with the outer air by many side shafts. The porous nature of the stone is assigned as the cause of the phenomenon. Daubeny (On Volcanoes) describes the remarkable basaltic deposits at Niedermennig--as he spells it--but says nothing of the existence of ice. Daubuisson[168] speaks of a _Schneegrube_, on a summit of the _Riesengebirge_, in Silesia, 4,000 feet above the sea; but such holes are common enough at that elevation, and I have seen two or three remarkable instances on the Jura, within the compass of one day's walk. Voigt[169] describes an _Eisgrube_ in the Rhöngebirge, on the _Ringmauer_, the highest point of the _Tagstein_, where abundant ice is found in summer under irregular masses of columnar basalt. Reich had received from a forest-inspector an account of an ice-hole in this neighbourhood, called _Umpfen_, which is apparently not the same as that mentioned by Voigt. In the Saxon Erzgebirge there are three points remarkable for their low temperature,[170] in addition to the mines on the Sauberg mentioned above. These are the _Heinrichssohle_, in the Stockwerk at Altenberg, where the mean of two years' observations gives the temperature 0°·54 F. lower at a depth of 400 feet than at the surface; the adit of _Henneberg_, on the Ingelbach, near Johanngeorgenstadt, where the temperature was again 0°·54 F. lower than in shafts some hundred feet higher; and the _Weiss Adler_ adit, on the left declivity of the valley of the Schwarzwasser, above the Antonshütte. It would appear that there are local causes which affect the temperature in the Erzgebirge, for Reich found that in several places the mean temperature of the soil was higher than that of the air: for instance-- Soil. Air. Height above the sea.