The fossils of the South Downs; or, Illustrations of the geology of Sussex

by Gideon Algernon Mantell

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1822 edition. ...localities, have produced similar examples. Geological Transactions, Vol. iv. p. 419. f From the correspondence of J. Hawkins, Esq. Obtuse rhomboidal crystals, of great beauty, have been found in a chalk-pit near Alfriston; their colour is of a delicate pearl white, and in their general appearance they resemble the double refracting spar of Iceland, except in their inferior degree of transparency. The cavities of echinites are sometimes lined with rhomboidal crystals of carbonate of lime, disposed in lines parallel with the sections formed by the areae of the shell; and the inner surfaces of the terebratulae, are frequently frosted over with drusy crystals of the same substance. 4. Sulphuret of iron, or iron pyrites, in subglobular and irregular masses, is very common in.the upper chalk. The external surface of the specimens is invested by crystals of a pyramidal, octaedral, or cubooctaedral form; and their interior exhibits a radiated structure, possessing a brilliant metallic lustre. When broken and exposed to the action of air and moisture, they undergo decomposition with great rapidity; and even in cabinets, frequently form an efflorescent sulphate of iron, and crumble into dust. This mineral occasionally incloses flints, shells, echinites, &c. and frequently fills up the cavities of the latter. A specimen in my possession, exhibits on the upper side, a sharp cast of the interior of an echino-spatagus; and its base is covered with an elegant group of quadrangular pyramids, evidently the terminations of octaedrons, with their inferior angles concealed. The lower beds of the flinty chalk in South-street, contain detached crystals of sulphuret of iron, remarkable for their neatness and elegant figure. They are usually regular...

108 pages, Paperback

First published September 30, 2010

About the author

English obstetrician, geologist and palaeontologist.