the geology and extinct volcanos of central france

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Seite 23 - Dome and the neighbouring domitic puys, consisting almost wholly of felspar, and therefore possessing the lowest possible specific gravity, and at the same time a very rude and coarse grain and highly porous structure, is precisely that species of lava which we should expect a priori to have possessed the minimum of fluidity when protruded into the air; * * See Considerations uii Vulcauuu, p.
Seite 8 - JEtao., when, in 1669, half their town was overwhelmed by one of its currents of lava. In the year 1751 two members of the Academy of Paris, Guettard and Malesherbes, on their return from Italy, where they had visited Vesuvius and observed its productions, passed through Montelimart, a small town on the left bank of the Ehone, and, after dining with a party of savans resident there, amongst whom was M.
Seite 33 - This amount of excavation can only be attributed to the river which still flows there, because the undisturbed and perfect state of the cone of loose scoriae demonstrates that no denuding wave, deluge, or extraordinary body of water has passed over this spot since the eruption.
Seite 32 - A constant emanation nation of carbonic acid gas takes place from its sides and bottom ; its mephitic qualities have b.een ascertained by repeated experiments.'* The surface of the last-mentioned current ' has been forced into cultivation by the most assiduous industry. The process is to break up all the projecting masses of basalt by blasting ; and from their fragments and scoriae, aided by dressings, a soil has been created and clothed with vineyards, which almost rivals the well-known fertility...
Seite 23 - ... hundred feet high. Exhausted by this effort, it proceeded but a short way down the bed of the stream towards the north, and stopped where the village of Mazayes now stands. The baffled waters of the Sioule here, as at Pont-Gibaud, obstructed by the rocky dyke thus suddenly thrown across their channel, must have given birth to a lake by their stagnation ; and would probably have ended, as in the other instance, by wearing away a passage parallel to their former one, had not the hill forming their...
Seite 37 - Vache, the point to wliich the lava rose in the crater is still marked by a projecting ridge of light scoriaceous matter of a reddish yellow colour, rich in specular iron, and considerably decomposed by sulphureous vapours; apparently part of the frothy scum which formed upon the surface of the ebullient lava, and adhered to the side of the vase at the moment of its being emptied.
Seite 49 - ... dykes of the same rocks.* The opposite sides of each excavation generally offer corresponding sections, the same beds being visible at similar heights on both declivities, but varying occasionally in thickness. This is universally the case in all the narrower gorges near the base of the mountain, where the diminished slope caused the lavacurrents to increase in width as much as in length ; and in these situations the same bed or series of beds often extends over a surface of many square miles,...
Seite 109 - The leading idea which is present in all our researches, and which accompanies every fresh observation, the sound which to the ear of the student of Nature seems continually echoed from every part of her works, is — Time! — Time! — Time!
Seite 111 - ... kinds of deer, the bear, hyaena, and many beasts of prey ranged the forest, or pastured on the plain, and were occasionally overtaken by a fall of burning cinders, or buried in flows of mud, such as accompany volcanic eruptions. Lastly, these quadrupeds became extinct, and gave place to [Post-Pliocene] mammalia, and these, in their turn, to species now existing. There are no signs, during the whole time required for this series of events, of the sea having intervened, nor of any denudation which...

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