10TH SEPTEMBER.--I set out on a fine clear morning, with two men and Yuranigh mounted, and leading two pack-horses carrying my sextant, false horizon, and a month's provisions. Returning, still up the valley, along our old track to Camp XLIII., I there struck off to the S.W., following up a similar valley, which came down from that side. This valley led very straight towards Mount Pluto, the nearest of the three volcanic cones, which I had already intersected from various points. The other two I had named Mount Hutton and Mount Playfair. These three hills formed an obtuse-angled triangle, whereof the longest side was to the north-west, and, therefore, I expected that there the elevated land might be found to form an angle somewhat corresponding with the directions of the two shorter sides; in which case, it was probable that, to the westward of such an angle in the range, I might find what had been so long the object of these researches, viz., a river flowing to the Gulf of Carpentaria. We reached Mount Pluto, at the distance given by my former observations as far as could be ascertained by the mode of measurement I employed then; which was by counting my horse's paces. On ascending the mountain on foot, I found a deep chasm still between me and the western summit, which was not only the highest, but the only part clear of bushes. A thick and very thorny scrub had already so impeded my ascent, that the best portion of the afternoon was gone, before I could return to the horses; and I resolved, therefore, to continue my ride, and to defer the ascent and observation of angles from the summit, until my return from the unknown western country, which we were about to explore; the search for water that night being an object of too much importance to be longer deferred. We, accordingly, passed on by the southward and westward of the mountain, following a watercourse, which led first N. W., then north, and next E. of N.; to where it at length joined one from the west, up which I turned, and continued the search for water until darkness obliged us to halt. During that search for water, my horse fell with me into a deep hole, so concealed and covered with long grass, that we both wholly disappeared from those following; and yet, strange to say, without either of us being in the least hurt. We encamped where there was, at least, good grass; but--no water.