a fossil found at Johangeorgenstad in Saxony, and at Joachimsthal in Bohemia, and is, by the miners, called Pechblende. M. Werner, a German mineralogist, being convinced that it was not a blend, gave it the name of *Perrum Ochraceum Picenum*, and thought it contained the tungstic acid combined with iron; but M. Klaproth is of a contrary opinion, and maintains that it is very different from wolfram. There are (he says) two varieties of pechblende: the one is of a dark grey colour, with very little brilliancy, the particles of which have the form of a flattened conchoïd; it is not very hard, and, when triturated, becomes a black powder: its mean specific gravity is 7.5. The other is distinguished by its black colour, though it sometimes afflumes a reddish tint: its surface is more brilliant than that of the former, and resembles pit-coal; it is also less hard; and the black powder, to which it is reduced by trituration, has a greenish hue. This kind is generally discovered in compact masses, lying between strata of a micaeous schist, which is found to be decomposed. In the internal parts of this stone, it is not uncommon to meet with veins of a peculiar yellow metallic earth. The pechblende is soluble in the nitric and in the nitro-muriatic acids, partially so in the muriatic, but not at all in the sulphuric. From these solutions, the unsaturated ferruginous prussiat of potash, or phlogisticated alkali, precipitates the metallic sublimate, which then resembles kermes mineral in colour. This, when it does not unite in flakes, but is uniformly diffused in the solution, may be considered as one of the most distinguishing characters of the pechblende; another is, that the precipitates, effected by the volatile and fixed alkalis, are yellow; the fixed caustic alkalis giving it a lemon colour, the aerated alike yellow. This yellow oxyd, or calx, cannot be fused with alkalis. As this fossil cannot be clasped either among the zinc or iron ores, and is very different from tungsten, M. Klaproth proposes to give it the appellation of Uranium; and he distributes it into the following species:

1. Uranium fulvoburatum. (a) Dark gray, often exhibiting traces of Galena. (b) Black, resembling pit-coal. 2. Uranium Ochraceum. Brimstone colour, lemon colour, deep yellow, reddish brown. 3. Uranium Spatheum. (a) Tinged with green by copper. (b) Yellow. This is the green mica or chalcolithe.