The wells are holes, about eighteen inches deep: the water has a slight taste of carbonate of soda, that was strong at first, but diminished greatly after some water had been drawn. The holes fill very fast. The saline impregnation arises, very probably, from the earth around falling, and being blown into the holes. Dibla is bounded on the north by black sandstone and quartz hills, which extend some way to the eastward; on the south by sand hills, and by a winding wadey on the east. In the middle there are several small conical hillocks with table-tops: the lower part is formed of a fine schistus, of different colours, that next the base light and white; over that, green, exactly resembling large well-dried leaves of plants, which separate into the finest layers; the top is a black bituminous matter, which crumbles into small pieces by the slightest touch: these hillocks are from thirty to forty feet high, the probable height of the valley in former days; and it is not unlikely that the bituminous matter is a vegetable deposit. There are a few acacias, but so few, that we could procure no firewood, and the camels very little food. A number of round semi-vitrified small stones were found on the sands, which the people collected to use as bullets. The mode of formation appears the same as the coralliform substances I have mentioned. These substances, in great quantities, are said to be formed after the rains that every now and then occur in this quarter.] [Footnote 20: There is grass in abundance, and small mounds covered with a tetrandrous plant, called suag: its fruit a small _drupa_, which is in great request in Bornou and Soudan, for removing sterility in females. Boo Khaloom related one instance of a female, who had been in that state eighteen years, but was cured by the fruit. It is sweetish and hot to the taste, approaching to the Sisymbrium nasturtium. In passing the plant, a heavy narcotic smell is always perceived.—W. O.] [Footnote 21: There is a very common grass which is grievously annoying from the prickles on its husk: it adheres to the dress and penetrates the skin. There is not one prickle, but the calyx is studded round, and they fasten themselves like grappling irons. These prickles may be considered one of the pests of the country: there is scarcely a place free from them. Our dog Niger is unable to walk, for they have got between his toes, and are adhering to every part of his long silken hair.] CHAPTER II. KOUKA.