Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/399

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The Basin of London, (Pl. 68.) affords an example of a similar disposition of the Tertiary strata reposing on the Chalk. The Basins of Paris, Vienna, and of Bohemia, afford other examples of the same kind. (See Pl. 1. Figs. 24—28.)

The Secondary and Transition strata of the central and North Western districts of England, are marginal portions of the great geological Basin of Northern Europe; and their continuations are found in the plains, and on the flanks of mountain regions on the Continents. The section (Pl. 66. Fig. I.) shows the manner in which the Strata of the Transition Series are continued downwards between the Coal formation and the older members of the Grauwacke formation through a series of deposites, to which, Mr. Murchison has recently assigned the name of the "Silurian system.". This Silurian System is represented by No. 11, in our Section, Fig. I. The recent labours of Mr. Murchison in the border counties of England and Wales have ably filled up what has hitherto been a blank page, in the history of this portion of the vast and important Systems of rocks, included under the Transition series; and have shown us the links which connect the Carboniferous system with the older Slaty rocks. The large group of deposites to which he has given the appropriate name of Silurian system, (as they occupy much of the Territory of the ancient Silures,) admits of a four-fold division, which is expressed in the section Pl. 66. Fig. 1. This section represents the exact order of succession of these Strata in a district, which must henceforth be classic in the Annals of Geology.

In September, 1835, I found the three uppermost divisions of this system, largely, developed in the same relative order of succession on the south frontier of the Ardennes, between the great Coal formation and the Grauwacke. See Proceedings of the Meeting of the Geological Society of France at Mézieres and Namur, Sep. 1835, (Bulletin de Ia Société Géologique dc France, Tom. VII.) The same subdivisions of the Silurian system, maintain their relative place and importance over a large extent of the mountainous district of the Eifel, between the Ardennes and the Valley of the Rhine; and are continued East of the Rhine through great part of the duchy of Nassau. (See Stiffts Gebirgs-Karte, von dem Herzogthum-Nassau. Wiesbaden, 1831.)

These general dispositions of all strata in the form of Troughs or Basins have resulted from two distinct systems of operations, in the economy of the terraqueous globe; the first producing sedimentary deposites, (derived from the materials