Collected Papers on Some Controverted Questions of GeologyMacmillan, 1895 - 279 pagina's |
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Collected Papers on Some Controverted Questions of Geology (1895) Joseph Prestwich, Jr. Geen voorbeeld beschikbaar - 2008 |
Veelvoorkomende woorden en zinsdelen
50 feet Aberdare Air in gallery antiquity areas Artesian beds bore-hole causes chalk plateau Coal-measures Colliery convection currents Cornwall crater Croll crust distance district duct Dukinfield earth effects Eocene eruption escape estimated evidence explosions Fahr feet deep fissures flints forms Geol geological periods Geologists Glacial epoch Glacial period glaciers Granite Greenland ground heat height holes hypothesis ice-sheet Journ lava lignite limestone lode mass mean annual mètres miles Miocene mountain Neolithic observations Palæolithic Physicists Plate Plateau drift plateau implements Pliocene Postglacial Preglacial Pregny present pressure question rate of increase rocks rude Sandstone Scrapers sea-level SECOND GROUP shaft Silurian specimens springs strata stream surface temperature Temp temperature Temperature at Depth Tertiary thermometer thermometric gradient thickness tion Triassic tunnel Uniformitarians valley drifts valley implements vapour ventilation Vesuvius volcanic West Yoke West Yoke Type Wheal
Populaire passages
Pagina 81 - If any doubt should suggest itself whether this fluid is actually generated within the lava, or only rises through it, having its origin in some other substance, or in some other manner, beneath, it must be dispelled by the evidence afforded in the extremely vesicular or cellular structure of very many erupted lavas, not merely near the surface, but throughout their mass, showing that the aeriform fluid in these cases certainly developed itself interstitially in every part.
Pagina 83 - The heat from which terrestrial volcanic energy is at present derived is produced locally within the solid shell of our globe by transformation of the mechanical work of compression or of crushing of portions of that shell, which compressions and crushings are themselves produced by the more rapid contraction, by cooling, of the hotter material of the nucleus beneath that shell, and the consequent more or less free descent of the shell by gravitation, the vertical work of which is resolved into tangential...
Pagina 80 - THE main agent in all these stupendous phenomena — the power that breaks up the solid strata of the earth's surface, raises, through one of the fissures thus occasioned, a ponderous column of liquid mineral matter to the summit of a lofty mountain, and launches thence into the air, some thousand feet higher, with repeated explosions, jets of this matter and fragments of the rocks that obstruct its efforts — consists unquestionably in the expansive force of some elastic aeriform fluid struggling...
Pagina 72 - ... are older than the valley drifts, I do not see how we are to avoid the conclusion, that not only was the plateau race not contemporary with the valley men, but also that the former belonged to a period considerably anterior to the latter — either an early glacial or a pre-glacial period.
Pagina 36 - ... the surface for great lengths of time. But either the evidence is insufficient or it points to slight temporary effects, except in one case, which is of more importance, and on which the greatest stress is laid, namely, that of Diirnten in Switzerland. There beds of lignite with mammalian remains are intercalated between two glacial deposits. Admitting the fact that the lignite rests on beds of undoubted glacial (groundmoraine) origin, and that the trees grew on the spot where their stumps and...
Pagina 1 - ... addition to the inherent difficulties of all dramatic work, there are just now many passing currents and sidewinds of modern public feeling to be understood and allowed for, many shoals and sandbanks of prejudice and cliquism to be left on one side. But land is in sight at last. HENRY ARTHUR JOXES. THE POSITION OF GEOLOGY THE position of geology in this country at the present time, more especially as relates to the later geological periods, is anomalous and possibly without precedent. On one...
Pagina 213 - After most careful consideration of the subject, and consultation with others who have also been engaged in this enquiry, it has been thought best to confine the observations, as much as possible to the temperature of the streams of water immediately issuing from the unbroken portions of the rocks and veins. The reasons for this preference are ; — that the temperature of the air in...
Pagina 103 - It is known that in several vents lava remains permanently fused without permanently overflowing. This shows that heat is brought up from below, not by continual supplies of melted rock, but by intensely heated gases passing through the lava. Under this view any disruption in the crust which is sufficient to permit the passage of steam at an enormous pressure, would originate a volcano. And much of the lava poured out might consist of the materials of the crust itself, fused by the passage of the...
Pagina 63 - Amongst these are the natural flints which have been selected for use as hammer or trimming stones, the result being that the flint has become chipped at the ends or round the sides undesignedly, but still in a manner that could not have resulted from natural wear. In a similar way, some are roughened at the end like the large pebbles or balls used at a later neolithic period, exhibiting patches of rough abraded surface, the result of repeated blows.