The lower part of the Adelaide having been already explored, prevented us from experiencing that depth of interest which we should otherwise have felt; still we were destined to enjoy our share of pleasurable sensations, as on the result of our examination depended the important fact of whether the river was navigable for large vessels. We therefore started to settle this momentous question, even before the eastern sky was tinted with orange from the rising of the sun, which in these latitudes gives no glimmering twilight: day fading and appearing instantaneously, the rapidity of the change presenting a remarkable effect. EXTENSIVE REACHES. Passing a narrow part, formed by two low red cliffy projections, we entered a wide reach that had an extensive flat of 2 and 2 1/2 fathoms water on the south side. The next was similarly circumstanced, the shoal water of the same depth, being, however, on the west side. Still in both there was a 3-fathom channel at low-water, and in the reaches above, seven in number, trending in a general South-South-East direction, about twice that depth. This imparted to our discoveries the stamp of utility, and as Captain Wickham found it navigable for thirty miles higher up where the water is fresh, we may pronounce the Adelaide the deepest river in Australia. MEET A CANOE. Proceeding upwards, we met a party of natives about seven miles from the mouth, in a very pretty bark canoe, fifteen feet long, and about two deep. The bark was sewn together with much neatness, and it was altogether the most artistic piece of workmanship I had seen among the Aborigines of Australia. It was the last of that description we met with in this direction, for we did not find canoes in use with the natives to the westward of Clarence Strait, but only rafts, a fact alluded to in an earlier portion of the work. ALARM OF THE NATIVES.