Geological Society. 425 



POSITIVE GEOtOGY. — EXTENSIVE RECOGNITION OF SILURIAN AND 

 DEVONIAN SYSTEMS ON THE CONTINENT. 



We may congratulate ourselves on the advance that has been 

 made during the past year, by the extension of our knowledge as 

 to the existence of the Silurian, Devonian and Carboniferous 

 systems over large districts of the continent of Europe. In my last 

 address I endeavoured to explain the reason why the old red 

 sandstone formation, which occupies so very extensive a place in 

 England, had been scarcely anywhere recognised on the Continent ; 

 namely, because we had till lately failed even in our own country to 

 refer to this system those extensive slaty forms of it, which, both 

 here and upon the Continent, had been referred to the grauvv^acke 

 of the Wernerian series, and had applied the name of old red sand- 

 stone only to a part of this formation, which had hitherto been con- 

 sidered as the type of the whole, namely, to the red marly, sandy, 

 and conglomerate strata of Herefordshire and the adjacent counties, 

 omitting the Killas and other slate-rocks of the Devonian system, 

 which Iiave now been shown to appertain to it. 



I further stated, that it would probably be found that this Devo- 

 nian system includes a large amount of strata upon the continent of 

 Europe, which had been hitherto known by the Wernerian name 

 Grauwacke ; and expressed my satisfaction that this name was likely 

 to retain its place in the nomenclature of geology, as a generic term 

 co-extensive with the transition series of the school of Freyberg, and 

 divisible into three great subordinate formations, namely, the De- 

 vonian, Silurian, and Cambrian systems. 



The labours of Professor Sedgwick and Mr. Murchison in the 

 Rhenish provinces and adjacent parts of Germany, in the summer of 

 1839, have furnished important additions to our knowledge of the 

 older rocks of the continent, and brought them into comparison Avith 

 the recently established pateocoic types of England ; the first efforts 

 of those authors were directed to the right bank of the Rhine, 

 where taking the coal-field of Westphalia as a fixed horizon, they 

 proceeded to deduce therefrom the descending order of the older 

 formations which emerge southwards from beneath that deposit, and 

 established a perfect sequence along a frontier of fifty miles in 

 length, from a true coal-field with carboniferous limestone down- 

 wards into Silurian rocks, by passing through an intermediate group 

 loaded with Devonian fossils*. 



a date anterior to their present curvilinear disposition in the form of basins. 

 He further shows, that the act of denudation was not confined to the di- 

 strict of the Weald along the lines of movement in which the greatest 

 elevations took place, but equally laid bare the highest summits of the 

 chalk hills and elevated plains, and swept away much of the contents of 

 the basins ; and endeavours to establish the connexion of these elevations 

 and subsidences with diluvial action, by showing that an adequate cause 

 for this action may be found in the elevatory movements produced by 

 forces acting upwards from the interior of the globe. 



* This order wjis not made clear until some startling difficulties were 

 overcome. All the German authorities had laid down as one continu- 



