In latitude 27 degrees, low sandstone tableland approached the west side of the river, and we attempted to travel along the slope between it and the mud plains, but found it so stony that the horses' hoofs were soon worn to the quick, as we had been compelled to remove their shoes to enable them to traverse the mud plains. Had it not been for green bushes of salsolae, and some similar plants which had sprung up since the rain, this tract of country exactly resembled the stony desert described by Captain Sturt as existing 200 miles to the westward. These remarkable features forming the declivities of the sandstone tableland through which Cooper's Creek forces its way, and by confining the waters to a narrower space during floods, causes the fine deep reaches of water which characterize it. 8th June. By following the western limits of the plains we reached latitude 27 degrees 30 minutes, when the sandstone tableland receded, and a boundless expanse of mud plain was before us; the lines of box-trees which had hitherto marked the channels nearly ceased, polygonum and atriplex constituting the main feature of the vegetation. COOPER'S CREEK. 9th June. After toiling south-west a day and a half over this level surface to latitude 27 degrees 50 minutes, we approached some low ridges, at the foot of which there was a lagoon 100 yards wide, exhibiting signs of a current during flood to the north-west; and as there was an evident westerly trend in all the smaller channels previously crossed, it was evident they would soon merge in Cooper's Creek. Steering west-north-west, the several channels collected together, and soon formed a deep watercourse, with fine reaches of water. The sandstone tableland closed in on both sides; the soil of the intervening plain was much firmer, but showed by the vegetation that saline nature which so often attends the development of the upper sandstones in Australia. Grass was abundant, and it was surprising with what rapidity the horses recovered their strength. BOUNDARY OF SOUTH AUSTRALIA. 12th June. Approaching the 141st meridian, which is the boundary of the province of South Australia, stony ridges closed in on both banks of Cooper's Creek, forming almost a natural division, across which we followed a well-beaten native path; and here I observed the only instance which has come under my observation where the aborigines have taken the trouble to remove natural obstacles from their paths. The loose stones had been cleared from the track, and in some places piled in large heaps. 14th June.