This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1822 Excerpt: ...a passage through their own interstices to the still purer siliceous matter, which is often crystallized in the form of quartz in the centre of the chalcedony, and so entirely surrounded by it, that it could have no access to its present place, except through the substance of the chalcedony, and the flint enclosing it. ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1822 Excerpt: ...a passage through their own interstices to the still purer siliceous matter, which is often crystallized in the form of quartz in the centre of the chalcedony, and so entirely surrounded by it, that it could have no access to its present place, except through the substance of the chalcedony, and the flint enclosing it." 3. Calcareous spar. This mineral is abundant in the fissures and hollows of the chalk, and forms the constituent substance of the shells and echinites. It is of various shades of amber colour, brown, and pearl white; the variety into which the shells and echinites are converted, is opaque, and has an oblique fracture. The other modifications generally possess some degree of transparency; in some of the larger bivalves, of the genus Inoceramus, the structure is fibrous. The crystals of carbonate of lime are of various forms; the most usual are the rhomboidal, columnar, and acicular. The first occurs abundantly in cavities in the chalk, ' immediately beneath the turf, on Plumpton Plain; and it is worthy of notice, that the hollows it occupies, have manifestly been formed subsequently to the consolidation of the chalk. In Western Sussex, branched cavities in the chalk, apparently occasioned by the decay of ramose zoophytes, are incrusted by this variety of calcareous sparf-. Of the columnar crystals, some fine specimens were brought to view by the tremendous fall of the cliffs near Beachy Head, that happened a few years since. These occurred in large masses of a yellowish colour, and the crystals when detached were semitransparent; Plumpton Plain, Alfriston chalk-pit, and some other localities, have produced similar examples. Geological Transactions, Vol. iv. p. 419. f-From the correspondence of J. Hawkins, Esq. Obtuse rhomboidal crystals, ...
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Add this copy of The Fossils of the South Downs: Or, Illustrations of to cart. $103.23, good condition, Sold by Bonita rated 4.0 out of 5 stars, ships from Newport Coast, CA, UNITED STATES, published 2010 by Cambridge University Press.
