Advanced Text-book of Geology, Descriptive and Industrial

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William Blackwood & Sons, 1856 - Geology - 325 pages
 

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Page 220 - With respect to the fishes of the tertiary epoch, " they are so nearly related," says M. Agassiz, " to existing forms, that it is often difficult, considering the enormous number (above 8000) of living species, and the imperfect state of preservation of the fossils, to determine exactly their specific relations. In general, I may say that I have not yet found a single species which was perfectly identical with any marine existing fish, except the little species which is found in nodules of clay,...
Page 312 - Switzerland to the longitudinal deposits of stony detritus which are found at the bases and along the edges of all the great glaciers. The formation of these accumulations is thus explained by Professor Agassiz : — The glaciers, it is well known, are continually moving downwards, in consequence, probably, of the introduction of water into their fissures, which, in freezing, expands the...
Page 225 - ... 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 be referred. All the mountain chains, such as the Alps, Pyrenees, Carpathians, and Himalayas, into the composition of whose central and loftiest parts the nummulitic strata enter bodily, could have had no existence till after the middle Eocene period."— Manual, p. 232. A still more...
Page 7 - In the preceding chapter we have endeavoured to explain that the object of geology is to investigate the structure of the earth, in as far as that structure is accessible to human investigation. Combining all we know of this rocky structure, from the top of the highest mountain to the bottom of the deepest mine, it forms but an insignificant film of the four thousand miles which lie between the surface and centre of the globe. This film or outer portion is spoken of as the " crust of the globe" in...
Page 287 - The laws of the organization of the earth are distinct and fixed as those of the animal frame, simpler and broader, but equally authoritative and inviolable. Their results may be arrived at without knowledge of the interior mechanism ; but for that very reason ignorance of them is the more disgraceful, and violation of them more unpardonable. They are in the landscape the foundation of all other truths...
Page 120 - The stratified rocks of the highest antiquity, such as the oldest gneiss or quartz rocks, have very seldom borne gold : but the sedimentary accumulations which followed, or the Silurian, Devonian, and Carboniferous (particularly the first of these three), have been the deposits which, in the tracts where they have undergone a metamorphosis or change of structure by the influence of igneous agency, or other causes, have been the chief sources whence gold has been derived.
Page 247 - ... deposits, marl is the only one whose formation deserves particular notice. This substance may be looked upon as the limestone of the superficial accumulations, just as the chalk, oolite, lias, zechstein, mountain limestone, and cornstone, were the calcareous beds of their respective formations. It occurs in various states of purity, from a marly clay, which will scarcely effervesce' with acids, to a shell-marl containing from 80 to 90 per cent, of lime. Marl-clay, for instance, occurs as a whitish...
Page 225 - When we have once arrived at the conviction that the numraulitic 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 be referred. All the mountain chains, such as the Alps, Pyrenees, Carpathians, and Himalayas, into the composition of whose central and loftiest parts the nummulitic strata enter bodily, could have had no existence till after...
Page 259 - The trunks of the trees gradually decay until they are converted into a blackish brown substance resembling peat, but which still retains more or less of the fibrous structure of the wood; and layers of this often alternate with layers of clay and sand, the whole being penetrated, to the depth of four or five yards or more, by the long fibrous roots of the willows. A deposition of this kind, with the aid of a little infiltration of bituminous matter, would produce an excellent imitation of coal,...

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