I however deemed it more prudent in the first instance to select the best route along which to move the whale-boat, as well as to choose a spot which afforded facilities for launching it. In pursuance of this determination we descended the eastern side of the sandhills which abruptly fell in that direction with a slope certainly not much exceeding an angle of 45 degrees. I now found that the water did not approach so near the foot of the hills as I had imagined, but that immediately at their base lay extensive plains of mud and sand, at times evidently flooded by the sea; for on them lay dead shells of many kinds and sizes, as well as large travelled blocks of coral. The water here appeared to be about a mile distant; it was also apparently boundless in an east and north-east direction: and was studded with islands. REMARKABLE PLAINS. DELUSION FROM MIRAGE. We still all felt convinced that it was water we saw, for the shadows of the low hills near it, as well as those of the trees upon them, could be distinctly traced on the unruffled surface. As we continued to advance, the water however constantly retreated before us and at last surrounded us. I now found that we had been deceived by mirage; the apparent islands being really such only when these plains are covered by the sea. In many places the sandy mud was so moist that we sank deeply into it, and after travelling for fifteen miles on a north-east course I could still see no limit to these plains in that direction, nor could I either then or on any subsequent occasion find the channel which connected them with the sea. The only mode of accounting for their being flooded is to suppose that the sea at times pours in over the low land which lies to the north of the Gascoyne, and flows northward through channels which will be seen in the chart of this part of the country; but I then believed, and still consider, that there is hereabouts a communication with some large internal water. We saw no tracks of natives and only a few of emus and native dogs. The few portions of rising ground which lay near the edge of these extensive plains were sandy, scrubby, and unpromising; but what we saw was so little that no opinion of the country could fairly be deduced from it. We dug in several places on the flats and in their vicinity but all the water we could find was salt; whereas in the narrow range of sandhills separating them from the sea we had discovered abundance of fresh water only four or five feet below the surface of the valleys lying between these hills. As this range of more than thirty miles in length offered many geological phenomena I called it Lyell's Range in compliment to the distinguished geologist of that name; the plains themselves I named the Plains of Kolaina (Deceit). INDISPOSITION OF SEVERAL OF THE PARTY. SICKNESS FROM DELAY AND DISAPPOINTMENT.