[Footnote 15: We passed two salt water lakes at a short distance on the west, which add much to the beauty of the scenery. There is something to-day quite cheering: large groves of palm trees, many beautiful acacias both in flower and fruit, and two fine, small salt lakes. The lakes are about two miles in circumference, have salt islands, and marshy borders: no salt, I believe, is taken from them. They are the abodes of a beautiful bird of the plover species.—W. O.] [Footnote 16: The lakes have marshy borders, and high salt islands, as if formed by man, which however are natural, and, the people say, have existed since their remembrance. The saline materials are a carbonate and muriate of soda: we saw no incrustations on the bottom or surface: at this season, the same is the case in the Bahr-Trona, in Fezzan. Each lake is not more than half or three-fourths of a mile in circumference.—W. O.] [Footnote 17: The hills run nearly north and south, edging a little to the westward; they have numerous small bays or recesses, which produce a fine echo; many places with saline incrustations, and some of the large black patches like the frozen surface of a recently ploughed field. Almost all the salt formations are in low, protected situations; the water is near; and, often in the very centre, you have fine fresh springs.—From whence is this salt derived? I have already suggested that the air has a powerful effect, and is a principal agent. There is no reason to believe there are large subterranean salt beds; if these existed to any great extent, we should not have the fresh springs so prevalent.—W. O.] [Footnote 18: We had a fine wadey the greater part of the way, and many patches of saline incrustations; some exposed beds of red sandstone, containing numerous nodules of iron ore. Hills of much blacker colour; and a few have the appearance as of ruins of towns and castles, on their summits. Passed three springs, like the oozings at Traghen. A large tract of black surface, as if the situation of an extensive salt bed, from which the salt had only been removed a few years; it extends more than four or five miles to the eastward, and was more than a mile across, on our road. It is black and crispy, but has none of the irregular heapings taken notice of in other salt plains.