vitreous feldspar, nor is any pumice-stone observable among them, but all the products of the volcano shew that it is a converted basalt. “The volcanic activity appears not to have extended far, and is only discovered on the northern margin of this cauldron, which was probably, at one time, a large sweet-water basin, for the stones of Sennaar in the north, those of Fazògl and Bertat in the east, of the country of Bari in the south, and of Kordofàn and Jebel Tira in the west, are of a different nature. “The collections in this city are derived partly from M. Werne, who made them in the expedition sent by the Basha of Egypt in the year 1840, and partly are owing to the scientific liberality of M. Russegger; and they afford sufficient information with respect to the general geognostic relations of these scarcely discovered mountains. “The chain of the Mountains of the Moon consists, according to the several specimens, of gneiss and mica-slate. One of these specimens, was taken from the most southerly point that the expedition reached, and indeed, ‘from the cataracts in the land of Bari;’ that is to say, from the rock which prevented the expedition from penetrating further into the country. It is gneiss, composed of white feldspar, and much black mica, and mica-slate; the friable and exceedingly granulous quartz does not contain feldspar, but small scaly black mica. There is found, moreover, in the valley of Berri, magnet iron-stone, which, however, does not seem to be commonly known; for it has been collected to the amount of several pounds weight, as being merely sand, without any other particles of stone.[11] “The magnet-iron displays also, in several places, brittle iron-ore, and reminds me of similar occurrences in the large mica-slate mountain-chain of the Brazils. “We do not possess, unfortunately, any specimens from the high mountains of Enarea, but the stones of the lands of Bertat, Sennaar, and Fazògl, are well known through M. Russegger’s excellent collection. There are granite and gneiss mountains in the land of Bertat, and in the southern part of Fazògl; chlorite slate (probably the stone bringing gold here) follows this chain towards the north, together with mica-slate; and lastly, in Sennaar, there is also clay-slate. In the latter, which is very much changed in some places, veins of granite and quartz are at the top, so that here also, as in many other points, the clay-slate appears the more ancient, the granite the more modern stone. Granite is met with likewise on the Bah’r el Abiad, in the Jebel Njemati (Iemati), being partly of pink feldspar, white albin, grey quartz and black mica, and partly composed without albin, and only of dark red feldspar, white quartz, and black mica.