New Text-Book of Geology; Designed for Schools and Academies

New Text-Book of Geology; Designed for Schools and Academies

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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. 1874 edition. Excerpt: ...some at the close of the Primordial, others at that of the Canadian or Trenton period, and some at the termination of subordinate epochs within these periods. The extermination of species took place at intervals through the periods, as well as at their close; though those at the latter were most universal. With the changes from one stratum to another there were disappearances of some species, and with the changes from one formation to another still larger proportions became extinct. No Primordial species are known to occur in the Canadian period; very few of the species of the Canadian period survive into the Trenton; and very many of those of the early part of the Trenton did not exist in the later part. Thus life and death were in progress together, species being removed, and other species appearing as time moved on. 3. Upper Silurian Era. I. Subdivisions. The Upper Silurian era in North America includes four periods: the Niagara, the Salina, the Lower Helderberg, and the Oriskany. The name of the first is from the Niagara River, along which the rocks are displayed; that of the second, from Salina in Central New York, the beds being the saltbearing rocks of that part of the State; that of the third, from the Helderberg Mountains, south of Albany, where the lower rocks are of this period; that of the fourth, from Oriskany, a place in Central New York, northwest of Utica. 2. Rocks: Kinds and Distribution. The rocks of the Niagara period are: 1. A conglomerate and grit-rock called the Oneida conglomerate, which extends from Central New York southward along the Appalachian region, having a thickness of 700 feet in some parts of Pennsylvania; together with shaly sandstones of the Medina group, which spread westward from Central New York more

Product details

  • Paperback | 100 pages
  • 189 x 246 x 5mm | 195g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236562550
  • 9781236562555