The first thing that strengthened in my mind this half-formed opinion, was the fall of the Lachlan into the Morumbidgee. I had been told that Australia was a basin; that an unbroken range of hills lined its coasts, the internal rivers of which fell into its centre, and contributed to the formation of an inland sea; I was not therefore prepared to find a break in the chain—a gap as it were for the escape of these waters to the coast.
Subsequently to our entrance into the Murray, the remarkable efforts of that river to maintain a southerly course were observed even by the men, and the singular runs it made to the south, when unchecked by high lands, clearly evinced its natural tendency to flow in that direction.
Had we found ourselves at an elevation above the bed of the Darling when we reached the junction of the principal tributary with the Murray, I should still have had doubts on my mind as to the identity of that tributary with the first-mentioned river; but considering the trifling elevation of the Darling above the sea, and that the junction was still less elevated above it, I cannot bring myself to believe that the former alters its course. It is not, however, on this simple geographical principle that I have built my conclusions; other corroborative circumstances have tended also to confirm in my mind the opinion I have already given, not only of the comparatively recent appearance above the ocean of the level country over which I had passed, but that the true dip of the interior is from north to south.
In support of the first of these conclusions, it would appear that a current of water must have swept the vast accumulation of shells, forming the great fossil bank through which the Murray passes from the northern extremity of the continent, to deposit them where they are; and it would further appear from the gradual rise of this bed, on an inclined plain from N.N.E. to S.S.W., that it must in the first instance, have swept along the base of the ranges, but ultimately turned into the above direction by the convexity of the mountains at the S.E. angle of the coast. From the circumstance, moreover, of the summit of the fossil formation being in places covered with oyster shells, the fact of the whole mass having been under water is indisputable, and leads us naturally to the conclusion that the depressed interior beyond it must have been under water at the same time.
It was proved by barometrical admeasurement, that the cataract of the Macquarie was 680 feet above the level of the sea, and, in like manner, it was found that the depot of Mr. Oxley, on the Lachlan, was only 500, there being a still greater fall of country beyond these two points. The maximum height of the fossil bank was 300 feet; and if we suppose a line to be drawn from its top to the eastward, that line would pass over the marshes of the two rivers, and would cut them at a point below which they both gradually diminish. Hence I am brought to conclude that in former times the sea washed the western base of the dividing ranges, at or near the two points whose respective elevations I have given; and that when the mass of land now lying waste and unproductive, became exposed, the rivers, which until then had pursued a regular course to the ocean, having no channel beyond their original termination, overflowed the almost level country into which they now fall; or, filling some extensive concavity, have contributed, by successive depositions, to the formation of those marshes of which so much has been said. I regret extremely, that my defective vision prevents me giving a slight sketch to elucidate whet I fear I have, in words, perhaps, failed in making sufficiently intelligible.
GEOLOGICAL REMARKS.
Now, as we know not by what means the changes that have taken place on the earth's surface have been effected, and can only reason on them from analogy, it is to be feared we shall never arrive at any clear demonstration of the truth of our surmises with regard to geographical changes, whether extensive or local, since the causes which produced them will necessarily have ceased to operate. We cannot refer to the dates when they took place, as we may do in regard to the eruptions of a volcano, or the appearance or disappearance of an island. Such events are of minor importance. Those mighty changes to which I would be understood to allude, can hardly be laid to the account of chemical agency. We can easily comprehend how subterranean fires will occasionally burst forth, and can thus satisfactorily account for earthquake or volcano; but it is not to any clashing of properties, or to any visible causes, that the changes of which I speak can be attributed. They appear rather as the consequences of direct agency, of an invisible power, not as the occasional and fretful workings of nature herself. The marks of that awful catastrophe which so nearly extinguished the human race, are every day becoming more and more visible as geological research proceeds. Thus, in the limestone caves at Wellington Valley, the remains of fossils and exuviae, show that their depths were penetrated by the same searching element that poured into the caverns of Kirkdale and other places. They are as gleams of sunshine falling upon the pages of that sublime and splendid volume, in which the history of the deluge is alone to be found; as if the Almighty intended that His word should stand single and unsupported before mankind: and when we consider that such corroborative testimonies of his wrath, as those I have noticed, were in all probability wholly unknown to those who wrote that sacred book, the discovery of the remains of a past world, must strike those under whose knowledge it may fall with the truth of that awful event, which language has vainly endeavoured to describe and painters to represent.
CHAPTER VIII.
Environs of the lake Alexandrina—Appointment of Capt. Barker to make a further survey of the coast near Encounter Bay—Narrative of his proceedings—Mount Lofty, Mount Barker, and beautiful country adjacent—Australian salmon—Survey of the coast—Outlet of lake to the sea—Circumstances that led to the slaughter of Capt. Barker by the natives—His character—Features of this part of the country and capabilities of its coasts—Its adaptation for colonization—Suggestions for the furtherance of future Expeditions.