ACCOMPANYING MARKS OF DISRUPTION. EARTHY DEPOSITS.
It may however be observed that the breccia is never found below ground without unequivocal proofs in the rocks accompanying it of disruption and subsidence, and that the best specimens of single bones have been found wedged between huge rocks, where the breccia occurs like mortar between them, in situations eight or ten fathoms underground.
THESE PHENOMENA COMPARED WITH OTHER EVIDENCE OF INUNDATION.
That changes have taken place in the relative level of land and sea is evident from the channel of the Glenelg which is worn in the rock to a depth of five fathoms below the sea level. The sea must have either risen, or the earth must have subsided, since that channel was worn by any current of water for it is now as still as a canal, the tide making a difference of only a few inches.
The features on the shores of Port Jackson extend underwater, preserving the same forms as they have above it; while the bays and coves now subject only to the ebb and flow of a tide present extensive ramifications, and can only be considered the submerged valleys of a surface originally scooped out by erosion at a period when the land stood higher above the sea.
SALT LAKES IN THE INTERIOR.
The hills on the margins of the Australian salt lakes are always on the north-east side, or opposite that of the prevailing south-west winds. The formation of these hills is probably due to the action of the wind, the growth and decomposition of small shells, the carbonate of lime disengaged by evaporation, and the concretion of calcareous matter and friable tuff so common in these ridges.
In two of the most remarkable, Mitre Lake and Greenhill Lake, a portion of the basin of each, between the hilly curves and the water, was filled by a dark-coloured perfectly level deposit, apparently of vegetable mould. This being of a quality different from that of the hills, it would appear that any process by which these heights may have originated through the agency of the water adjacent and the wind could not continue after this different formation had accumulated between them. Accordingly where this dark-coloured deposit is most extensive the curved hill concentric with the outer margin seems less perfect; but whether worn by time or sweeping inundations I cannot pretend to say.
That some affinity exists between such accumulations and the salt water in the lakes is the more probable from the present state of those of Cockajemmy, which occur in the bed of a former current, and between the rocky sides of a kind of ravine. Even in such a situation a mound of very firm ground has been formed on the eastern bank of each, and was found very convenient for the passage of the ravine by the carts of the party. (See above.)
In those hills beside salt lakes on the plains a tendency to regular curvature was the chief feature: the relative situation with respect to the water and the wind was always the same; while in some cases, where grassy flats had once been lakes, crescent-shaped green mounds were still apparent on the north-eastern sides of each. If these remains of salt water are of less volume than they have been formerly, as may be presumed from these circumstances; and if the waters according to Professor Faraday's analysis "are solutions of common salt and, except in strength, very much resemble those of the ocean,"* we cannot have much difficulty in believing that the sea deposited the water in these situations at no very remote period.