Saturday, July 6.—At 2. 40. started with a beautiful moonlight, over a sandy plain, with a great many small hillocks. We stopped at Dalhoon, a well nearly filled up with sand, and containing water so brackish that we were unable to drink it. We started again, and got in among the sand hills. Our new guide proved neither such an active man nor experienced pilot as our old Tuarick, as we had several times to retrace our steps. Monday, July 8.—We entered the wadey Trona early this morning, on the north-east side. Near where we entered there are a cluster of date palms, and a small lake, from which impure trona is obtained. On the western side the trona lake is surrounded with date trees, and its marshy borders are covered on almost all sides by grass, and a tall juncus. It is about half a mile long, and nearly two hundred yards wide. At present it is of inconsiderable depth, from the evaporation of the water; for many places are dry now, which are covered in the winter and spring. The trona crystallizes at the bottom of the lake, when the water is sufficiently saturated; for when the water is in large quantities it eats the trona, as the people say. The cakes vary in thickness, from a fine film to several inches (two or three). The thickest at present is not more than three-fourths of an inch; but in the winter, when the water begins to increase, it is of the thickness I have mentioned. The surface next the ground is not unequal from crystallization, but rough to the feel, from numerous small rounded asperities. That next the water is generally found studded with numerous small, beautiful vertical crystals of muriate of soda; the line of junction is always distinct, and the one is easily removed from the other. When not covered with muriate of soda, the upper surface shows a congeries of small tabular pieces joined in every position. When the mass is broken there is a fine display of reticular crystals, often finely radiated. The surface of the water is covered in many places with large thin sheets of salt, giving the whole the appearance of a lake partially frozen over: film after film forms, till the whole becomes of great thickness. Thus may be observed, on the same space, trona and cubical crystals of muriate of soda, and, on the surface of the water, films accumulating, till the whole amounts to a considerable thickness. The soil of the lake is a dark brown sand, approaching to black, of a viscid consistence, and slimy feel; and, on the lately uncovered surface of the banks, a black substance, something like mineral tar, is seen oozing out. The water begins to increase in the winter, and is at its height in the spring. In the beginning of the winter the trona is thickest and best, but in the spring it disappears entirely. The size of the lake has diminished considerably within the last nine years; and, if care be not taken, the diminution will soon be much more considerable; for plants are making rapid encroachments, and very