Cotham Marble Enlarge
Aug. 1. 1809. Publish’d by Jas Sowerby London.
British Mineralogy

Cotham Marble

  • Syn. Argillo-Calcite. Kirw.

Cotham, near Bristol, affords this remarkably figured Marie , which, according to the Bristol Guide, you may often imagine is a fine drawing. It is a curious formation of Marie and Clay, chiefly stained by Iron, and perhaps occasionally by Manganese, forming, by settling in moisture under peculiar circumstances, the top undulations, sometimes representing clouds in a sky, while the bottom imitates earth and water as in landscapes. The fanciful figure to themselves in this something like a boat and men in one part, and hedge-rows in another, with trees in full foliage. The appearance of the different parts seems in a great measure to point out the different substances, The whiter part is softer, and has most Lime; the bluer or grayer have a dilute mixture of the black Oxide of Iron; the browner part being still harder in consequence of the state of the Oxide of Iron, and the quantity of Clay or Alumine; for it must be remembered that Clay often has much Silex mixed with it. The deposition indicates the mass to have been more fluid in some parts than in others; and perhaps some conjecture might be formed as to the trees having distilled in drops from the upper waved surface; but at present we must rest with the theory, the practice of which may lead to useful and certain truths. This substance is found in broad slabs, and is cut transversely from the thickness of an inch to a foot or more. It is sometimes admired for ornamental chimney pieces, and the masons in the neighbourhood have used a great deal of it for such purposes.

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