Sand; stones; little ridges of quartzose limestone; granite mixed with red sandstone or white; a few mimosas, at intervals of one or two days’ march; abrupt pinnacles breaking the dull level of the sandstones; dry and bushless valleys—such were the features of the country through which Dr. Barth and his companions wearily plodded. Herds of buffaloes, however, are numerous; as is also, in the higher ground, the _Ovis tragelaphis_. On the 16th of August the travellers, while descending a rocky crest covered with gravel, came in sight of Mount Asben. The Asben or A’ir is an immense oasis, which has some claim to be considered the Switzerland of the Desert. The route pursued by Dr. Barth on his way to Agadez traversed its most picturesque portion, where, almost every moment, the great mountain revealed itself, with its winding gorges, its fertile basins, and its lofty peaks. Agadez is built on a plain, where it seems to lament that the day of its prosperity has passed. At one time it was the centre of a considerable commerce; but, since the close of the last century, its population has sunk from sixty thousand to seven or eight thousand souls. Most of its houses lie in ruins; the score of habitations which compose the palace are themselves in a deplorably dilapidated condition; of the seventy mosques which it previously boasted only two remain. The richer merchants shun the market of Agadez, which is now in the possession of the Touats, and supported by small traders, who do a little business in the purchase of millet when the price is low.