impression, that this immense tract of land had formerly been an archipelago of islands, and that the apparently boundless plains into which I had descended on my former expeditions, were, or rather had been, the sea-beds of the channels, which at that time separated one island from the other; it was impossible, indeed, to traverse them as I had done, and not feel convinced that they had at one period or the other been covered by the waters of the sea. It naturally struck me, that if I was correct in this conjecture, the difficulty or facility with which the interior might be penetrated, would entirely depend on the breadth and extent of these once submarine plains, which in such case would now separate the available parts of the continent from each another, as when covered with water they formerly separated the islands. This hypothesis, if I may so call it, was based on observations which, however erroneous they may appear to be, were made with an earnest desire on my part to throw some light on the apparently anomalous structure of the Australian interior. No one could have watched the changes of the country through which he passed, with more attention than did I--not only from a natural curiosity, but from an anxious desire to acquit myself to the satisfaction of the Government by which I was employed.

When Mr. Oxley, the first Surveyor-General of New South Wales, a man of acknowledged ability and merit, pushed his investigations into the interior of that country, by tracing down the rivers Lachlan and Macquarie, he was checked in his progress westward by marshes of great extent, beyond which he could not see any land. He was therefore led to infer that the interior, to a certain extent, was occupied by a shoal sea, of which the marshes were the borders, and into which the rivers he had been tracing discharged themselves.

My friend, Mr. Allan Cunningham, who was for several years resident in New South Wales, and who made frequent journeys into the interior of the continent as botanist to his late Majesty King George IV. and who also accompanied Captain P. P. King, during his survey of its intertropical regions, if he did not accompany Mr. Oxley also on one of his expeditions, strongly advocated the hypothesis of that last-mentioned officer; but as Mr. Cunningham kept on high ground on his subsequent excursions, he could not on such occasions form a correct opinion as to the nature of the country below him. His impressions were however much influenced by the observations made by Captain King in Cambridge Gulf, the water of which was so much discoloured, as to lead that intelligent and careful officer to conclude, that it might prove to be the outlet of the waters of the interior, and hence a strong opinion obtained, that the dip of the continent was in the direction of that great inlet, or to the W. N. W. I therefore commenced my investigations, under an impression that I should be led to that point, in tracing down any river I might discover, and that sooner or later I should be stopped by a large body of inland waters. I descended rapidly from the Blue Mountains, into a level and depressed interior, so level indeed, that an altitude of the sun, taken on the horizon, on several occasions, approximated very nearly to the truth. The circumference of that horizon was unbroken, save where an isolated hill rose above it, and looked like an island in the ocean.

When I reached the point at which Mr. Oxley had been checked, I found the Macquarie, not "running bank high," as he describes it, but almost dry; and although ten years had passed since his visit to this distant spot, the grass had not yet grown over the foot-path, leading from his camp to the river; nor had a horse-shoe that was found by one of the men lost its polish. In this locality there are two hills, to which Mr. Oxley gave the names of Mount Harris and Mount Foster, distant from each other about five miles, on a bearing of 45 degrees to the west of south. Of these two hills Mount Foster is the highest and the nearest, and as the Macquarie runs between them to the westward, it must also be closer than Mount Harris to the marshes. I therefore naturally looked for any discovery that was to be made from Mount Foster, and I according ascended that hill just as the sun was setting. I looked in vain however for the region of reeds and of water, which Mr. Oxley had seen to the westward; so different in character were the seasons, and the state of the country at the different periods in which the Surveyor-General and I visited it. From the highest point I could gain I watched the sun descend; but I looked in vain for the glittering of a sea beneath him, nor did the sky assume that glare from reflected light which would have accompanied his setting behind a mass of waters. I could discover nothing to intercept me in my course. I saw, it is true, a depressed and dark region in the line of the direction in which I was about to go. The terrestrial line met the horizon with a sharp and even edge, but I saw nothing to stay my progress, or to damp my hopes. As I had observed the country from Mount Foster, so I found it to be when I advanced into it. I experienced little difficulty therefore in passing the marshes of the Macquarie, and in pursuing my course to the N. W. traversed plains of great extent, until at length I gained the banks of the Darling, in lat. 30 degrees. S. and in long. 146 degrees. E. This river, instead of flowing to the N. W. led me to the S. W.; but I was ultimately obliged to abandon it in consequence of the saltness of its waters. I could not, however, fail to observe that the plains over which I had wandered were wholly deficient in timber of any magnitude or apparently of any age, excepting the trees which grew along the line of the rivers; that the soil of the plains was sandy, and the productions almost exclusively salsolaceous. Their extreme depression, indeed their general level, since they were not more than 250 or 300 feet above the level of the sea, together with their general aspect, instinctively, as it were, led the mind to the conviction that they had, at a comparatively recent period, been covered by the ocean. On my return to the Blue Mountains, and on a closer examination of the streams falling from them into the interior, I observed that at a certain point, and that too nearly on the same meridian, they lost their character as rivers, and soon after gaining the level interior, terminated in marshes of greater or less extent; and I further remarked that at certain points, and that too where the channels of the rivers seemed to change, certain trees, as the swamp oak, casuarina, and others ceased, or were sparingly to be found on the lower country--a fact that may not be of any great importance in itself, but which it is still as well to record. The field, however, over which I wandered on this occasion was too limited to enable me to draw any conclusions applicable to so large a tract of land as the Australian continent. On this, my first expedition, I struck the Darling River twice, 1st, as I have stated in latitude 30 degrees S. and in long. 146 degrees; and seconndly, in lat. 30 degrees 10 minutes 0 seconds S., and in long. 147 degrees 30 minutes E. From neither of these points was any elevation visible to the westward of that river, but plains similar to those by which I had approached it continued beyond the range of vision or telescope from the highest trees we could ascend; beyond the Darling, therefore, all was conjecture.

At the close of the year 1829, I was again sent into the interior to trace its streams and to ascertain the further course of the Darling. I proceeded on this occasion to the south of Sydney, and intersecting the Murrumbidgee, a river at that time but little known, but which Mr. Hume had crossed, in lat. 35 degrees 10 minutes, and long. 147 degrees 28 minutes 30 seconds E., on his journey to the south coast, at a very early period of discovery, and which thereabouts is a clear, rapid and beautiful stream. I traced it downwards to the west to lat. 34 degrees 44 minutes, and to long. 143 degrees 5