But too soon we left this charming strip of cultivation, and ascended the rocky ground on our right, above which again rose several detached hills, one of which had so interesting and well-marked a shape that I sketched its outlines. The road which we followed is not the common one. The latter, after crossing very rugged ground for about fifteen miles, keeps along the fine deep valley Télwa for about ten miles, and then ascending for about an hour, reaches Ágades in three hours more. This latter road passes by Tímelén, where at times a considerable market is said to be held. [Illustration] Having descended again, we found the ground in the plain covered with a thin crust of natron, and further on met people busy in collecting it; but it is not of very good quality, nor at all comparable to that of Múnio or to that of the shores of Lake Tsád. There are several places on the border between the desert and the fertile districts of Negroland, which produce this mineral, which forms a most important article of commerce in middle Sudán. Another well-known natron-district is in Zabérma; but in Western Sudán natron is almost unknown, and it is only very rarely that a small sample of it can be got in Timbúktu. Many of the Kél-owí have learnt (most probably from the Tedá or Tébu) the disgusting custom of chewing tobacco intermixed with natron, while only very few of them smoke. The monotony of the country ceased when we entered the valley Búdde, which, running in the direction of our path from S.S.W. to N.N.E., is adorned with a continuous strip of dúm-trees, besides abísga and talha; but the latter were of rather poor growth in the northern part of the valley. Having crossed at noon the broad sandy watercourse, which winds through the rich carpet of vegetation, and where there happened to be a tolerably large pond of water, we encamped in the midst of the thicket. Here the mimosas attained such an exuberance as I had scarcely observed even in the valley Ásada, and being closely interwoven with “gráffeni” or climbing plants, they formed an almost impenetrable thicket. From the midst of this thorny mass of vegetation a beautiful ripe fruit, about an inch and a half long, of the size of a date, and of dark-red colour, awakened the desire of the traveller; but having eaten a few, I found them, though sweet, rather mawkish.