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.
Captain Flinders, in describing the position of the chains of islands on the north-west coast of Carpentaria, Wessel's, the English Company's, and Bromby's Islands, remarks, that he had "frequently observed a great similarity both in the ground plans, and the elevations of hills, and of islands, in the vicinity of each other, but did not recollect another instance of such a likeness in the arrangement of clusters of islands."* The appearances which called for this observation, from a voyager of so much sagacity and experience in physical geography, must probably have been very remarkable; and, combined with information derivable from the charts, and from the specimens for which we are indebted to Captain King and Mr.Brown, they would seem to point out the arrangement of the strata on the northern coasts of New Holland.
(*Footnote.

The following are the proportions assigned by Captain de Freycinet to the principal divisions of the globe.

Voyage aux Terres Australes page 107.
COLUMN 1: DIVISION OF THE GLOBE.
COLUMN 2: AREA IN FRENCH LEAGUES SQUARE.
COLUMN 3: PROPORTION.
Asia : 2,200,000 : 17.
America : 2,100,000 : 17.
Africa : 1,560,000 : 12.
Europe : 501,875 : 4.
Australia : 384,375 : 3.
The most remote points from the coast of New South Wales, to which the late expeditions have penetrated (and the interior has never yet been examined in any other quarter) are not above 500 miles, in a direct line from the sea; the average width of the island from east to west being more than 2000 miles, and from north to south more than 1000 miles.) (*Footnote.