(*Footnote. Peron Voyage etc. volume 2 pages 165 to 183.)
(**Footnote. Geological Transactions Second Series volume 1 page 403, 404.)
(***Footnote. The statements here referred to, are those of Mrs. Graham, in a letter to Mr. Warburton, which has been published in the Geological Transactions Second Series volume 1 page 412, etc.; and the account is supported and illustrated by a valuable paper in the Journal of the Royal Institution for April 1824 volume 17 page 38 etc.) The writer of this latter article asserts that the whole country, from the foot of the Andes to far out at sea, was raised by the earthquake; the greatest rise being at the distance of about two miles from the shore. The rise upon the coast was from two to four feet: at the distance of a mile, inland, it must have been from five to six, or seven feet, pages 40, 45.)
M. Peron has attributed the great abundance of the modern breccia of New Holland to the large proportion of calcareous matter, principally in the form of comminuted shells, which is diffused through the siliceous sand of the shores in that country;* and as the temperature, especially of the summer, is very high on that part of the coast where this rock has been principally found, the increased solution of carbonate of lime by the percolating water, may possibly render its formation more abundant there, than in more temperate climates. But the true theory of these concretions, under any modification of temperature, is attended with considerable difficulty: and it is certain that the process is far from being confined to the warmer latitudes. Dr. Paris has given an account of a modern formation of sandstone on the northern coast of Cornwall;** where a large surface is covered with a calcareous sand, that becomes agglutinated into a stone, which he considers as analogous to the rocks of Guadaloupe; and of which the specimens that I have seen, resemble those presented by Captain Beaufort to the Geological Society, from the shore at Rhodes. Dr. Paris ascribes this concretion, not to the agency of the sea, nor to an excess of carbonic acid, but to the solution of carbonate of lime itself in water, and subsequent percolation through calcareous sand; the great hardness of the stone arising from the very sparing solubility of this carbonate, and the consequently very gradual formation of the deposit--Dr. MacCulloch describes calcareous concretions, found in banks of sand in Perthshire, which present a great variety of stalactitic forms, generally more or less complicated, and often exceedingly intricate and strange,*** and which appear to be analogous to those of King George's Sound and Sweer's Island: And he mentions, as not unfrequently occurring in sand, in different parts of England (the sand above the fossil bones of Norfolk is given as an example) long cylinders or tubes, composed of sand agglutinated by carbonate of lime, or calcareous stalactites entangling sand, which, like the concretions of Madeira, and those taken for corals at Bald-Head, have been ranked improperly, with organic remains.
(*Footnote. Peron Voyage etc. 2 page 116.)
(**Footnote. Transactions of the Geological Society of Cornwall volume 1 page 1 etc.)
(***Footnote. On an arenaceo-calcareous substance, etc. Quarterly Journal Royal Institution October 1823 volume 16 page 79 to 83.)
The stone which forms the fragments in the breccia of New Holland, is very nearly the same with that of the cement by which they are united, the difference consisting only in the greater proportion of sand which the fragments contain: and it would seem, that after the consolidation of the former, and while the deposition of similar calcareous matter was still in progress, the portions first consolidated must have been shattered by considerable violence. But, where no such fragments exist, the unequal diffusion of components at first uniformly mixed, and even the formation of nodules differing in proportions from the paste which surrounds them, may perhaps admit of explanation, by some process analogous to what takes place in the preparation of the compound of which the ordinary earthenware is manufactured; where, though the ingredients are divided by mechanical attrition only, a sort of chemical action produces, under certain circumstances, a new arrangement of the parts.* And this explanation may, probably, be extended to those nodular concretions, generally considered as contemporaneous with the paste in which they are enveloped, the distinction of which, from conglomerates of mechanical origin, forms, in many cases, a difficulty in geology. What the degree may be, of subdivision required to dispose the particles to act thus upon each other, or of fluidity to admit of their action, remains still to be determined.
(*Footnote. The clay and pulverized flints are combined for the use of the potter, by being first separately diffused in water to the consistence of thick cream, and when mixed in due proportion are reduced to a proper consistence by evaporation. During this process, if the evaporation be not rapid and immediate, or if the ingredients are left to act on each other, even for twenty-four hours, the flinty particles unite into sandy grains, and the mass becomes unfit for the purposes of the manufacturer. I am indebted for this interesting fact, which, I believe, is well known in some of the potteries, to my friend Mr. Arthur Aikin. And Mr. Herschel informs me, that a similar change takes place in recently precipitated carbonate of copper; which, if left long moist, concretes into hard gritty grains, of a green colour, much more difficultly soluble in ammonia than the original precipitate.)
6. As the superficial extent of Australia is more than three-fourths of that of Europe, and the interior may be regarded as unknown,* any theoretic inferences, from the slight geological information hitherto obtained respecting this great island, are very likely to be deceitful; but among the few facts already ascertained respecting the northern portion of it, there are some which appear to afford a glimpse of general structure.