Class-book of GeologyMacmillan and Company, 1891 - 516 páginas |
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Términos y frases comunes
abundant abundantly accumulated acid Ammonites basin beds bones bottom Brachiopods calcareous calcite Cambrian carbonate of lime Carboniferous Chapter characteristic chiefly clay containing corals Cretaceous crinoids crystalline crystals decay deposits detritus Devonian earth earth's crust Eocene eruptive rocks Europe evidence example extinct fauna feet thick felspar fishes fissures formations fossils genera geological history geologist glacier globe gradually granite gravel ground iron Jurassic kinds known lakes land lava layers limestone living lower marine marls mass materials Mesozoic miles Miocene molten mountains natural North occur Old Red Sandstone organic remains original Palæozoic period Permian plants and animals Pliocene present preserved probably quartz rain regions represented rivers sand schists sea-floor sediment sedimentary rocks shales sheets shells siliceous Silurian slopes soil solid sometimes species stone strata stratified stream structure substance surface terrestrial Tertiary trace Triassic Trilobites upper valley various vegetation vent volcanic
Pasajes populares
Página 11 - Time, which antiquates antiquities, and hath an art to make dust of all things, hath yet spared these minor monuments.
Página 57 - The travertine of Tuscany is deposited at the Baths of San Vignone at the rate of six inches a year, at San Filippo one foot in four months. At the latter locality it has been piled up to a depth of at least 250 feet, forming a hill a mile and a quarter long and a third of a mile broad.
Página 262 - ... globe, is by no means a proof of the freshwater origin of the latter fishes. The immense interval of time implied by the comparison renders its value somewhat problematical. Sir A. Geikie, in referring to the fishes of the Old Red Sandstone, says : " That some of the fishes found their way to the sea, as our modern salmon does, is indicated by the occasional occurrence of their remains among those of the truly marine fauna of the Devonian rocks.
Página 227 - Yet there can be no doubt that the planet must have had a long history before the appearance of any of the solid portions now to be seen.
Página 69 - Britain by land, as in late pleistocene times the land extended over the greater part of what is now the bed of the North Sea as far as Shetland and into the Atlantic beyond the Hebrides.
Página 321 - The stream not improbably descended from the north or northwest. It carried down the drifted vegetation of the land, with occasional carcases of the iguanodons and other terrestrial or amphibious creatures of the time. Beyond the area overspread by the sand and mud of the delta, the ordinary marine sediments accumulated, with their characteristic organic remains. From Yorkshire, England, they stretch eastward through north\vestern Germany, and are found at the base of the Cretaceous system through...
Página 139 - A mass of matter composed of one or more simple minerals, having usually a variable chemical composition, with no necessarily symmetrical external form, and ranging in cohesion from loose debris up to the most compact stone." It is in this sense that the word rock is used in geology. In common usage, however, the term is restricted to consolidated beds. It is also true that the word rock is more commonly used in speaking of large masses while still in the ground; while to smaller pieces...
Página 136 - ... salt lakes. A few small deposits are due to the action of sulphuric acid upon limestone; and the hydration of anhydrite may be responsible for a small amount of gypsum. The color varies from pure white to gray, brown, pink and black. Massive gypsum is generally distinctly granular. It is so soft as to be easily cut with a knife. The strata vary in thickness from a few inches to twenty, thirty or forty feet. It occurs at many points both east and west of the mountains in Colorado. TRAVERTINE,...
Página 366 - It is undoubtedly the greatest triumph of geological science to have demonstrated that the present plants and animals of the globe were not the first inhabitants of the earth, but that they have appeared only as the descendants of a vast ancestry, the latest comers in a majestic procession, which has been marching through an unknown series of ages. At the head of this procession we ourselves stand, heirs of all the progress of the past and moving forward into the future wherein progress towards something...
Página 228 - Towards the centre of the nebula the heaviest elements might be expected to condense, and there the high temperature would longest continue. The sun is the remaining intensely hot nucleus of the original nebula, from which heat is still radiated to the furthest part of the system. When a planetary ring broke up, and by the heat thereby generated was probably reduced to the state of...