General remarks — Result of the expedition — Previous anticipations — Mr. Oxley’s remarks — Character of the Rivers flowing westerly — Mr. Cunningham’s remarks — Fall of the Macquarie — Mr. Oxley’s erroneous conclusions respecting the character of the interior, naturally inferred from the state in which he found the country — The marsh of the Macquarie merely a marsh of the ordinary character — Captain King’s observations — Course of the Darling — Character of the low interior plain — The convict Barber’s report of rivers traversing the interior — Surveyor-General Mitchell’s Report of his recent expedition.
Result of the Expedition.

Whether the discoveries that have been made during this expedition, will ultimately prove of advantage to the colony of New South Wales, is a question that time alone can answer. We have in the meanwhile to regret that no beneficial consequences will immediately follow them. The further knowledge that has been gained of the interior is but as a gleam of sunshine over an extensive landscape. A stronger light has fallen upon the nearer ground, but the distant horizon is still enveloped in clouds. The veil has only as it were been withdrawn from the marshes of the Macquarie to be spread over the channel of the Darling. Unsatisfactory, however, as the discoveries may as yet be considered in a commercial point of view, the objects for which the expedition had been fitted out were happily attained. The marsh it had been directed to examine, was traversed on every side, and the rivers it had been ordered to trace, were followed down to their terminations to a distance far beyond where they had ceased to exist as living streams. To many who may cast their eyes over the accompanying chart, the extent of newly discovered country may appear trifling; but when they are told, that there is not a mile of that ground that was not traversed over and over again, either by Mr. Hume or by myself, that we wandered over upwards of 600 miles more than the main body of the expedition, on different occasions, in our constant and anxious search for water, and that we seldom dismounted from our horses, until long after sunset, they will acknowledge the difficulties with which we had to contend, and will make a generous allowance for them; for, however unsuccessful in some respects the expedition may have been, it accomplished as much, it is to be hoped, as under such trying circumstances could have been accomplished. It now only remains for me to sum up the result of my own observations, and to point out to the reader, how far the actual state of the interior, has been found to correspond with the opinions that were entertained of it.
Mr. Oxley’s Remarks.

I have already stated, in the introduction to this work, that the general impression on the minds of those best qualified to judge was, that the western streams discharged themselves into a central shoal sea. Mr. Oxley thus expresses himself on the subject:—

“July 3rd. Towards morning the storm abated, and at day-light, we proceeded on our voyage. The main bed of the river was much contracted, but very deep; the waters spreading to the depth of a foot or eighteen inches over the banks, but all running on the same point of bearing. We met with considerable interruptions from fallen timber, which in places nearly choked up the channel. After going about twenty miles, we lost the land and trees; the channel of the river, which lay through reeds, and was from one to three feet deep, ran northerly. — This continued for three or four miles farther, when, although there had been no previous change in the breadth, depth, or rapidity of the stream for several miles, and I was sanguine in my expectations of soon entering the long-sought-for Australian sea, it all at once eluded our farther pursuit, by spreading on every point from N.W. to N.E. among the ocean of reeds which surrounded us, still running with the same rapidity as before. There was no channel whatever among those reeds, and the depth varied from three to five feet. This astonishing change (for I cannot call it a termination of the river) of course left me no alternative but to endeavour to return to some spot on which we could effect a landing before dark. I estimated, that during the day, we had gone about twenty-four miles, on nearly the same point of bearing as yesterday. To assert, positively, that we were on the margin of the lake, or sea, into which this great body of water is discharged, might reasonably be deemed a conclusion, which has nothing but conjecture for its basis. But if an opinion may be permitted to be hazarded from actual appearances, mine is decidedly in favour of our being in the immediate vicinity of an inland sea, or lake, most probably a shoal one, and gradually filling up by numerous depositions from the high lands, left by the waters which flow into it. It is most singular, that the high lands on this continent seem to be confined to the sea-coast, and not to extend to any distance from it.”
Mr. Cunningham’s Remarks.

In a work published at Sydney, containing an account of Mr. Allan Cunningham’s journey towards Moreton Bay, in 1828, the following remarks occur, from which it is evident Mr. Cunningham entertained Mr. Oxley’s views of the character and nature of the Western interior. Towards the conclusion of the narrative, the author thus observes:—

“Of the probable character of the distant unexplored interior, into which it has been ascertained ALL the rivers falling westerly from the dividing ranges flow, some inference may be drawn from the following data.

“Viewing, between the parallels of 34 degrees and 27 degrees, a vast area of depressed interior, subjected in seasons of prolonged rains to partial inundation, by a dispersion of the several waters that flow upon it from the eastern mountains whence they originate; and bearing in mind at the same time, that the declension of the country within the above parallels, as most decidedly shown by the dip of its several rivers, is uniformly to the N.N.W. and N.W., it would appear very conclusive, that either a portion of our distant interior is occupied by a lake of considerable magnitude, or that the confluence of those large streams, the Macquarie, Castlereagh, Gwydir, and the Dumaresq, with the many minor interfluent waters, which doubtless takes place upon those low levels, forms one or more noble rivers, which may flow across the continent by an almost imperceptible declivity of country to the north of north-west coasts, on certain parts of which, recent surveys have discovered to us extensive openings, by which the largest accumulations of waters might escape to the sea.”
Character of the Rivers.

It is the characteristic of the streams falling westerly from the eastern, or coast ranges, to maintain a breadth of channel and a rapidity of current more immediately near their sources, that ill accords with their diminished size, and the sluggish flow of their waters in the more depressed interior. In truth, neither the Macquarie nor the Castlereagh can strictly be considered as permanent rivers. The last particularly is nothing more than a mountain torrent. The Macquarie, although it at length ceased to run, kept up the appearance of a river to the very marshes; but the bed of the Castlereagh might have been crossed in many places without being noticed, nor did its channel contain so much water as was to be found on the neighbouring plains.

There are two circumstances upon which the magnitude, and velocity of a river, more immediately depend. The first is the abundance of its sources, the other the dip of its bed. If a stream has constant fountains at its head, and numerous tributaries joining it in its course, and flows withal through a country of gradual descent, such a stream will never fail; but if the supplies do not exceed the evaporation and absorption, to which every river is subject, if a river dependant on its head alone, falls rapidly into a level country, without receiving a single addition to its waters to assist the first impulse acquired in their descent, it must necessarily cease to flow at one point or other. Such is the case with the Lachlan, the Macquarie, the Castlereagh, and the Darling. Whence the latter originates, still remains to be ascertained; but most undoubtedly its sources have been influenced by the same drought that has exhausted the fountains of the three first mentioned streams.

In supporting his opinion of the probable discharge of the interior waters of Australia upon its north-west coast, Mr. Cunningham thus remarks in the publication from which I have already made an extract.

“To those remarkable parts of the north-west coast above referred to in the parallel of 16 degrees south, the Macquarie river, which rises in lat. 33 degrees, and under the meridian of 150 degrees east, would have a course of 2045 statute miles throughout, while the elevation of its source, being 3500 feet above the level of the sea as shown by the barometer, would give its waters an average descent of twenty inches to the mile, supposing the bed of the river to be an inclined plane.

“The Gwydir originating in elevated land, lying in 31 degrees south, and long. 151 degrees east, at a mean height of 3000 feet, would have to flow 2020 miles, its elevated sources giving to each a mean fall of seventeen inches.

“Dumaresq’s river falling 2970 feet from granite mountains, in 28 1/4 degrees under the meridian of 152 degrees, would have to pursue its course for 2969 miles, its average fall being eighteen inches to a mile.”

As I have never been upon the banks either of the Gwydir or the Dumaresq, I cannot speak of those two rivers; but in estimating the sources of the Macquarie at 3500 feet above the level of the sea, Mr. Cunningham has lost sight of, or overlooked the fact, that the fall of its bed in the first two hundred miles, is more than 2800 feet, since the cataract, which is midway between Wellington Valley and the marshes, was ascertained by barometrical admeasurement, to be 680 feet only above the ocean. The country, therefore, through which the Macquarie would have to flow during the remainder of its course of 1700 miles, in order to gain the N.W. coast, would not be a gradually inclined plain, but for the most part a dead level, and the fact of its failure is a sufficient proof in itself how short the course of a river so circumstanced must necessarily be.
Mr. Oxley’s Opinions.

Having conversed frequently with Mr. Oxley on the subject of his expeditions, I went into the interior prepossessed in favour of his opinions, nor do I think he could have drawn any other conclusion than that which he did, from his experience of the terminations of the rivers whose courses he explored. Had Mr. Oxley advanced forty, or even thirty miles, farther than he did, to the westward of Mount Harris; nay, had he proceeded eight miles in the above direction beyond the actual spot from which he turned back, he would have formed other and very different opinions of the probable character of the distant interior. But I am aware that Mr. Oxley performed all that enterprise, and perseverance, and talent could have performed, and that it would have been impracticable in him to have attempted to force its marshes in the state in which he found them. It was from his want of knowledge of their nature and extent, that he inferred the swampy and inhospitable character of the more remote country, a state in which subsequent investigation has found it not to be. The marsh of the Macquarie is nothing more than an ordinary marsh or swamp in another country. However large a space it covers, it is no more than a concavity or basin for the reception of the waters of the river itself, nor has it any influence whatever on the country to the westward of it, in respect to inundation; the general features of the latter being a regular alternation of plain and brush. These facts are in themselves sufficient to give a fresh interest to the interior of the Australian continent, and to increase its importance.
Capt. King’s Opinions.

With respect to that part of its coast at which the rivers falling from the eastern mountains, discharge themselves, it is a question of very great doubt. It seems that Capt. King, in consequence of some peculiarities in the currents at its N.W. angle, supports Mr. Cunningham’s opinion as to their probable discharge in that quarter. But I fear the internal structure of the continent is so low, as to preclude the hopes of any river reaching from one extremity of it to the other. A variety of local circumstances, as the contraction of a channel, a shoal sea, or numerous islands, influence currents generally, but more especially round so extensive a continent as that of which we are treating; nor does it strike me that any observations made by Capt. King during his survey, can be held to bear any connection with the eastern ranges, or their western waters. It may, however, be said, that as the course of the Darling is still involved in uncertainty, the question remains undecided; but it appears to me, the discovery of that river has set aside every conjecture (founded on previous observation) respecting the main features of the interior lying to the westward of the Blue Mountains. Both Mr. Oxley and Mr. Cunningham drew their conclusions from the appearances of the country they severally explored. The ground on which those theories were built, has been travelled over, and has not been found to realise them, but subsequent investigation has discovered to us a river, the dip of whose bed is to the S.W. We have every reason to believe that the sources of this river must be far to the northward of the most distant northerly point to which any survey has been made, as we are certain that it is far beyond the stretch of vision from the loftiest and most westerly of the barrier ranges; from which circumstance, it is evident that whatever disposition the streams descending from those ranges to the westward may show to hold a N.W. course more immediately at the base, the whole of the interior streams, from the Macquarie to the Dumaresq, are tributaries to the principal channel which conveys their united waters at right angles, if not still more opposite to the direction they were supposed to take, as far as is yet known.
Course of the Darling.

The Darling River must be considered as the boundary line to all inland discoveries from the eastward. Any judgment or opinion of the interior to the westward of that stream, would be extremely premature and uncertain. There is not a single feature over it to guide or to strengthen either the one or the other.
Character of the Western Interior.

My impression, when travelling the country to the west and N.W. of the marshes of the Macquarie, was, that I was traversing a country of comparatively recent formation. The sandy nature of its soil, the great want of vegetable decay, the salsolaceous character of its plants, the appearance of its isolated hills and flooded tracts, and its trifling elevations above the sea, severally contributed to strengthen these impressions on my mind. My knowledge of the interior is, however, too limited to justify me in any conclusion with regard to the central parts of Australia. An ample field is open to enterprise and to ambition, and it is to be hoped that some more decisive measures will be carried into effect, both for the sake of the colony and of geography, to fill u............