We pushed onwards in the cool of the morning, taking a South 20 degrees West direction, for three miles, crossing the eastern part of the flat to which we yesterday gave the name of Thirsty Flat, and found the soil a light mould, covered with long dry grass. This brought us to a bend in the river, trending in rather a tortuous manner east, and passing through a wide valley, with table ranges, varying from 5 to 600 feet on either side. Towards their summits there were perpendicular cliffs of some 30 or 40 feet, similar to the high land of Sea Range. The country just here was so thickly wooded that I was obliged to climb a tree in order to get the bearings. We noticed some very curious black horizontal streaks on the hills in our immediate vicinity. We crossed the river, or rather over its bed--a patch of stones--and found some shells of the water-tortoise at the remains of a native fire on the bank: we named the reach Tortoise Reach, in consequence. Here too Mr. Bynoe added some rare and beautiful specimens of finches to his collection. ENERVATING EFFECT OF THE GREAT HEAT. The cool north-west wind had now deserted us, and though yet scarcely nine o'clock A.M. the thermometer stood at 105 degrees. I had again the good fortune to shoot a kangaroo: it was a long cross-shot, the animal going at speed. Our route now lay across a barren stony plain, of which the vegetation it might once have boasted had been burnt off: the blackened ground, heated by the fierce rays of the sun, seemed still to us on fire. In crossing a creek which lay in our path, and which we managed to do by means of a fallen tree, Mr. Forsyth showed symptoms of being struck with the sun, but a little water, which I was happy enough to get from the creek, revived him. Several others of the party also complained of the trying effects of the great heat; after a short rest, I therefore determined on making for the river, which we arrived at in half an hour, near a bed of dry rocks, but with the reaches on either side wide and deep, and shut in by steep banks. By this time one of the men was seriously indisposed; all hopes, therefore, of proceeding much further upon this most interesting expedition I was compelled, though very reluctantly, to abandon. This was still the more a subject of deep regret, because the present width, and the south-easterly direction which the river now appeared to take, gave me just hopes that great progress might be made in the desired direction in the course of another day: while I felt satisfied that we were abandoning the course of a river whose undiminished magnitude made each mile's journey along its banks of increased interest, and which I felt convinced would, if followed out, conduct us far towards the heart of this terra incognita.