PROCEEDINGS 



THE GEOLOGICAL SOCIETY OF LONDON. 



Vol. II. 1838. No. 58. 



May 23. — A memoir entitled, a Synopsis of the English series of 

 stratified rocks inferior to the old red sandstone — with an attempt 

 to determine the successive natural groups and formations. By the 

 Rev. Adam Sedgwick, Woodwardian Professor in the University of 

 Cambridge, commenced on the 21st March, was concluded. 



Introduction. — The author, after stating what was now offered to 

 the Society to be only a first approximation, involving many questions 

 of difficulty and doubt, pointed out the principles on which he had 

 undertaken the task. There are two elements of classification ap- 

 plicable to stratified rocks of all ages, viz., physical structure and 

 order of superposition; one giving the mineralogical unity of a 

 group of rocks, the other their relative age. In addition to the two 

 former, are classifications founded on the organic remains in the 

 several groups. In the commencement of geology the last method 

 was only subsidiary to the two former. But after observations had 

 been multiplied, laws respecting the distribution of organic types 

 were discovered, which not merely superseded, in many large for- 

 mations, all classifications founded on mineral structure ; but often, 

 through wide regions, gave indications of succession which were 

 unsupported by the direct evidence of sections. As, however, the 

 (so called) laws respecting the distribution of organic types, are 

 mere general results grounded on actual observation, it is obvious 

 that they can never upset conclusions drawn from the clear and un- 

 ambiguous evidence of sections. The two methods may be used ■ 

 independently, and conspire to the same end ; but in their nature 

 cannot come into permanent collision. 



The author then points out some examples in which these principles 

 had been violated. (1) The attempt formerly made by some geolo- 

 gists to arrange the Stonesfield slate in a tertiary group, merely from 

 the presence of certain fossils of a class not commonly found in second- 

 ary rocks. (2) Some of the doctrines put forth in the papers of M. 

 Deshayes, which if pushed to their utmost extent would make the 

 evidence of sections of no value ; whereas without sections fossils 

 could never have led to any general laws of succession. (3) The 

 recent discussions respecting the age of the culm plants of North 

 Devon. The plants were assumed to be of the age of the greywacke, 



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