Transactions of the Geological Society Volume 2, PT. 2

Transactions of the Geological Society Volume 2, PT. 2

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1827 edition. Excerpt: ...and hypothetical character. Whatever doubts may exist as to the exact manner in which many of these rocks have been produced on the surface of the globe, still enough is known and generally recognized concerning the phaenomena in which they originate, to show that with them the collocation of similar beds is no proof of their contemporaneous production. In the sedimental and arenaceous rocks, we infer the age of a whole stratum or series of strata from the observed geological relations of one of their parts, notwithstanding the solutions of continuity or the concealment of intervening portions, that may separate this from the remaining mass. But amongst volcanic rocks we know that by the side of a mass of early date, one of recent formation may be produced tomorrow, exactly similar to the former in mineral composition. And in reality the natural tendency of the volcanic phaenomena is by no means to produce vast and extensive formations at a single epoch; but on the contrary, to form partial masses, one by one, at very distant intervals of time, which yet often agree most closely in their mineralogical characters. This is a consideration too much overlooked by some late authors, who, assuming the contemporaneous formation of whole districts of trachyte or basalt, have inferred their place in the geological series by the observed relations of one or two isolated members. In the case under consideration, if we assume that the graystone of Ponza, Ventotiene, and San Stefano, belongs to the same period, which their nearly equal state of preservation seems to authorize, (and perhaps the analogous formations of Procida, Ischia, and the Phlegraean fields may be referred to the same age, ) the superposition of this rock in Ponza to the trachyte, more

Product details

  • Paperback | 86 pages
  • 189 x 246 x 5mm | 168g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236651847
  • 9781236651846