Discourses Biological and Geological: Essays

Macmillan, 1894 - 388 páginas

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Página 14 - Globigerince, with the granules which have been mentioned, and some few other calcareous shells ; but a small percentage of the chalky mud — perhaps at most some five per cent, of it — is of a different nature, and consists of shells and skeletons composed of silex, or pure flint. These silicious bodies belong partly to the lowly vegetable organisms which are called Diatomaceoe, and partly to the minute, and extremely simple, animals, termed Radiolaria. It...
Página 13 - Globigerince of every size, from the smallest to the largest, are associated together in the Atlantic mud, and the chambers of many are filled by a soft animal matter. This soft substance is, in fact, the remains of the creature to which the Globigerina shell, or rather skeleton, owes its existence — and which is an animal of the simplest imaginable description. It is, in fact, a mere particle of living jelly, without defined...
Página 22 - This is a kind of shell-fish, with a shell composed of two pieces, of which, as in the oyster, one is fixed and the other free. " The upper valve is almost invariably wanting, though occasionally found in a perfect state of preservation in the white chalk at some distance. In this case, we see clearly that the sea-urchin first lived from youth to age, then died and lost its spines, which were carried away. Then the young Crania adhered to the bared shell, grew and perished in its turn; after which,...
Página 32 - Indians. Crocodiles of modern type appear ; bony fishes, many of them very similar to existing species, almost supplant the forms of fish which predominate in more ancient seas ; and many kinds of living shell-fish first become known to us in the chalk.
Página 244 - But the great tragedy of Science — the slaying of a beautiful hypothesis by an ugly fact...
Página 6 - Or, to take a more familiar example, the fur on the inside of a teakettle is carbonate of lime, and, for anything chemistry tells us to the contrary, the chalk might be a kind of gigantic fur upon the bottom of the earth-kettle, which is kept pretty hot below.

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