The Student's Elements of Geology

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John Murray, 1878 - 672 Seiten
 

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Seite 143 - cainos, recent, because the fossil shells of this period contain an extremely small proportion of living species, which may be looked upon as indicating the dawn of the existing state of the testaceous fauna, no recent species having been detected in the older or secondary rocks. The term Miocene (from
Seite 444 - named by Agassiz Cephalaspis, or " buckler-headed," from the extraordinary shield which covers the head (see Fig. 502), and which has often been mistaken for that of a trilobite, such as Asaphus. A species of -Pteraspis, of the same family, has also been found by the Rev. Hugh Mitchell in Fig. 503.
Seite 275 - separate Scinde from Persia, and which form the passes leading to Caboul; and it has been followed still farther eastward into India, as far as eastern Bengal and the frontiers of China. posed by him to be related both to the bear and to the Kinkajou (Cercoleptes). This creature appears to be the oldest known tertiary
Seite 580 - la Beche, has intruded itself into the carboniferous slate and slaty sandstone, twisting and contorting the strata, and sending veins into them. Hence some of the slate rocks have become " micaceous; others more indurated, and with the characters of mica-slate and gneiss; while others again appear converted into a hard zoned rock strongly impregnated with feldspar."f
Seite 549 - from the crater of every active volcano to a great depth below, perhaps several miles or leagues, and the effects which are produced deep in the bowels of the earth may, or rather must, be distinct; so that volcanic and plutonic rocks, each different in texture, and sometimes even in composition, may originate simultaneously
Seite 559 - rocks, are frequently observed to contain metals, at or near their junction with stratified formations. On the other hand, the veins which traverse stratified rocks are, as a general law, more metalliferous near such junctions than in other positions. Hence it has been inferred that these metals may have been spread in
Seite 26 - the ample limits of his domain, and admit, at the same time, that not only the exterior of the planet, but the entire earth, is but an atom in the midst of the countless worlds surveyed by the astronomer. The materials of this crust are not thrown together confusedly ; but distinct mineral masses, called rocks, are
Seite 197 - Crag may be partly derived from this source. White or Coralline Crag.—The lower or Coralline Crag is of very limited extent, ranging over an area about twenty miles in length, and three or four in breadth, between the rivers Stour and Aide, in Suffolk. It is generally calcareous and marly—often a mass of comminuted shells,
Seite 29 - are all characterized by stratification or fossils, or by both. Volcanic Rocks.—The division of rocks which we may next consider are the volcanic, or those which have been produced at or near the surface whether in ancient or modern times, not by water, but by the action of fire or subterranean heat. These rocks
Seite 528 - of stratified clay, the laminae of which are occasionally subdivided by thin arenaceous layers. These strata dip to the NW, and rest on a mass of columnar lava (see Fig. 599) in which the tops of the pillars are weathered, and so rounded as to be often hemispherical. In some places in the adjoining

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