III. — On the Geological Relations and internal Strnctnre of the Mag- 

 nesiaii Tjimeslone, and the lower Portions of the Neiv lied Sandstone 

 Series in their Range through Nottinghamsliire, Derbyshire, York- 

 shire, and Durham, to the Southern Extremity of Northwnherland. 



By the Rev. A. SEDGWICK, V.P.G.S. F.R.S. 



WOODWARDIAN PROFESSOR IN THE UNIVERSITY OF CAMBRIDGE. 



[Read November 17th, 1826; April 30th, May 18th, 1827; and March 7th, 1828.] 



Chapter I. § 1. Introduction. 



IT is my intention in the following communication to describe the principal 

 phaenomena exhibited by the great deposit of magnesian limestone which 

 stretches on the eastern skirt of the central chain of our island, from the 

 neighbourhood of Nottingham to the southern extremity of Northumberland. 

 I had, in the year 1821, an opportunity of examining several portions of this 

 deposit (especially in the county of Durham), and of verifying some interest- 

 ing details connected with it which had appeared in the Transactions of the 

 Society*. During a part of the two following summers I examined its whole 

 western escarpment, and most of the localities which seemed likely to show its 

 general relation, or to throw light on the structure of its subordinate parts, 1 

 venture to hope that a connected account of these observations, to which many 

 additions have been made during subsequent visits to certain parts of the for- 

 mation, may not be thought unworthy the attention of this Society. 



After the production of the rocks of the carboniferous order, the earth's sur- 

 face appears to have been acted on by powerful disturbing forces, which, not 

 only in the British Isles, but through the greater part of the European basin, 

 produced a series of formations of very great extent and complexity of struc- 

 ture. These deposits (known in our own country by the name of new red 

 sandstone and red marl, and when considered on an extended scale, com- 

 prising all the formations between the coal-measures and the lias), notwith- 

 standing their violent mechanical origin, have several characters in common, 



* Geol. Trans. Old Series, vol, iv. pp. 3—10. 



