Elements of Geology

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John Murray, 1865 - 794 pagina's
 

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Pagina 416 - Germany, is an alternation of thin beds of blue or grey limestone, having a surface which becomes light-brown when weathered, these beds being separated by dark-coloured narrow argillaceous partings, so that the quarries of this rock, at a distance, assume a striped and riband-like appearance. The Lias has been divided in England into three groups, the Upper, Middle, and Lower.
Pagina 392 - The regular and uniform preservation of this thin bed of black earth over a distance of many miles, shows that the change from dry land to the state of a fresh-water lake or estuary, was not accompanied by any violent denudation, or rush of water, since the loose black earth, together with the trees which lay prostrate on its surface, must inevitably have been swept away had any such violent catastrophe taken place.
Pagina 308 - When we have once arrived at the conviction that the nummulitic formation occupies a middle place in the Eocene series, we are struck with the comparatively modern date to which some of the greatest revolutions in the physical geography of Europe, Asia, and northern Africa must bo referred.
Pagina 502 - ... which contains a larger proportion of hydrogen than wood does. A continuance of decomposition changes this lignite into common or bituminous coal, chiefly by the discharge of carburetted hydrogen, or the gas by which we illuminate our streets and houses.
Pagina 731 - ... or in the dry way, but that they have been derived from liquid solutions, or in the wet way — a process requiring a far less intense degree of heat. Thermal springs, charged with carbonic acid and with hydrofluoric acid (which last is often present in small quantities), are powerful causes of decomposition and chemical reaction in rocks through which they percolate.
Pagina 5 - ... we infer that these strata have been generally spread out by the action of water, from what we daily see taking place near the mouths of rivers, or on the land during temporary inundations. For, whenever a running stream charged with mud or sand has its velocity checked, as when it enters a lake or sea, or overflows a plain, the sediment, previously held in suspension by the motion of the water, sinks by its own gravity to the bottom. In this manner layers of mud and sand are thrown down one...
Pagina 416 - ... assumed that the 17.6 cc. of milk taken for the determination will weigh 10 times as much as 2 cc. of warm butter fat. It is important that the final readings be taken while the fat is still warm. On account of the unavoidable contraction of the fat while taking these readings it is customary to read from the bottom of the lower to the top of the upper meniscus. The result is usually within 0.2 per cent of that found by the gravimetric method. The column of fat should be of a clear yellow color...
Pagina 67 - Britain,' you will learn that in Wales, and the contiguous parts of England, a maximum thickness of 32,000 feet (more than six miles), of carboniferous, Devonian and Silurian beds, has been measured, the whole formed whilst the bed of the sea was continuously and tranquilly subsiding. In illustration of a movement of the same kind, I need scarcely remind you of the coal-measures of South Wales, with their numerous under-clays, each containing Stigmaria, a...
Pagina 118 - Fig. 87, but also in No. 4, or the higher gravels, as at St. Acheul, in the suburbs of Amiens, where the old alluvium lies at an elevation of about 100 feet above the level of the river Somme. At both levels fluviatile and land-shells are met with in the loam as well as in the gravel, but there are no marine shells associated, except at Abbeville, in the lowest part of the gravel, near the sea, and a few feet only above the present high-water1 mark.
Pagina 60 - An epoch still more remote presented itself, when even the most ancient of these rocks, instead of standing upright in vertical beds, lay in horizontal planes at the bottom of the sea, and was not yet disturbed by that immeasurable force which has burst asunder the solid pavement of the globe. Revolutions still more remote appeared in the distance of this extraordinary perspective. The mind seemed to grow giddy by looking so far into the abyss of...

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