We were about to leave, at last, this extraordinary stream on which we had sojourned so long, enjoying abundance of excellent water in the heart of a desert country. From the sparkling transparency of this water, its undiminished current, sustained without receiving any tributary throughout a course of 660 miles, and especially from its being salt in some places and fresh at others, it seems probable that the river, when in that reduced state, is chiefly supported by springs. It would appear that the saltness occurs in the greatest body of water where no current was perceptible, and as this was excessive when the river was first discovered, it may be attributed to saline springs, due to beds of rock-salt in the sandstone or clay. The bed of the river is on an average about sixty feet below the common surface of the country. To this depth the soil generally consists of clay in which calcareous concretions and selenite occur abundantly; but at some parts the clay, charged with iron, forms a soft kind of rock in the bed or banks of the river. There are no traces of watercourses on these level plains such as might be expected to fall from the hills behind; though the latter contain hollows and gullies, which must in wet seasons conduct water to the plains. The distance of such heights from the river is seldom less than twelve miles; and it would appear that the intervening country is of such an absorbent nature that any water falling in torrents from the hills is imbibed by the soft earth, or is received in the deep broad cracks which sear the hollow parts, and in wet seasons must take up much water and retain it, until either evaporated or sunk to lower levels. The water may thus be absorbed and retained for a considerable time, or until it is carried by slow drainage into the river, especially where the lower parts of such plains are shut in by hills approaching the channel. Thus, where the extremity of Dunlop's range shot forward into the wide level margin, we found that the water had lost all taste of salt, a circumstance most easily accounted for by supposing that springs, being more abundant there from the near vicinity of the hills, had diluted the water which we had found salt higher up. That some tributary or branch joins the river from the opposite bank, at or near the sweep it describes round the hill, is not unlikely. I could not conveniently examine that part from our side, and hence it remains doubtful whether the problem admits of such easy solution. TRACES OF FLOODS.