OTHER FORMATIONS DISPOSED IN BASINS. 395 



The Basin of London, (PI. 68.) affords an example of a 

 similar disposition of the Tertiary strata reposing on the 

 <]Ihalk. The Basins of Paris, Vienna, and of Bohemia, 

 afford other examples of the same kind. (See PI. 1. Figg. 

 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 Continent.* 



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 ma- 



* The section (PI. 66. Fig. 1.) shows the manner in which the Strata of 

 the Transition Series are continued downwards between the Coal forma- 

 tion 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 Sj'stem is represented by No. 11, in our 

 Section, Fig. 1. The recent labours of Mr. Murchison in the border coun- 

 ties 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 

 oi! 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, 1 835, 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 Grau- 

 wacke. See Proceedings of the Meeting of the Geological Society of France 

 at Mezieres and Namur, Sep, 1835, Bulletin de la Societc Geologique de 

 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, (StifRs Gebirgs-Karte, von dcm Herzogthum-Nassau. Wiesbaden, 

 1831.) 



