• 



2 Prof. BucKLAND and Mr. De la Beche on the 



escarpment of the chalk downs and the sea. We shall designate this tract 

 by the general appellation of the Weymouth District : it is a tract of no 

 small importance in the geological history of England : — 



1. Prom its position near the south-western termination of several principal 

 formations of this island, including tertiary strata, chalk, greensand, Purbeck 

 and Portland beds, several members of the oolite formation, and lias. 



2. As exhibiting a coast section which forms an interesting object of com- 

 parison with the north-eastern terminations of the same strata on the coast 

 of Yorkshire, which have recently been so well described by Mr. Phillips*, 

 and with their appearance across the Channel on the coast of Normandy, the 

 details of which have been described by Mr. De la Beche in the Geological 

 Transactions f, and subsequently by M. de Caumont in his Essay on the 

 Department of Calvados J. 



3. As affording remarkable examples of violent disturbances which have 

 affected all these strata since the period of their consolidation ; producing 

 elevations, depressions, fractures, and denudations, connected and continuous 

 with those which have operated so extensively in Purbeck and the Isle of 

 Wight, and through the wealds of Sussex and Kent. 



We shall take a short review of the general physical features of this district 

 before we enter upon geological details. It will be seen by reference to our 

 map§, which is on the same scale as the Ordnance Survey, that the physical 

 features of the coast are: — 1. On the east a range of high cliffs extending 

 from the chalk of White Nore to the flat marsh lands of Lodmore near Wey- 

 mouth. 2. The marsh lands of Lodmore, divided only by a bank of pebbles 

 from the waters of Weymouth Bay. 3. A low range of cliffs, extending from 

 Weymouth Harbour to Portland Ferry. 4. The remarkable accumulation of 

 pebbles called the Chesil Bank, extending from the northern extremity of 

 Portland about sixteen miles north-westward to Burton Castle, and causing 

 the sea to be separated from the main land along nearly half this district by a 

 backwater called the Fleet. 3. A succession of cliffs rising gradually from Bur- 

 ton towards the west till they attain their highest elevation of about 600 feet 

 in the summit of the Golden Cap Hill, between Bridport and Charmouth. 



The physical features of the interior divide it into two distinct compart- 

 ments, which we shall call the Vale of Weymouth and the Vale of Bredy. 



The Vale of Bredy is bounded on the north and east by lofty escarpments of 



* Illustrations of the Geology of Yorkshire, by John Phillips, Esq. F.G.S. York, 1829. 

 ■j- Geological Transactions, Second Series, vol. i. Part I. p. 40 — 47. 



;J; Essai stir la Topographie Geognostique du Departement du Calvados, par M. de Caumont. 

 Caen, 1828. § Plate I. 



