8 Prof. BucRLAND and Mr. De la Beche on the 



to a small distance only from their native place. The cliffs at Axmouth and 

 near Sidmouth exhibit deposits of such miscellaneous diluvial gravely resting- 

 on red marl, and adjacent to beds of uniform and angular chalk-flint breccia 

 that rest on the chalk. 



These deposits of breccia on the coast of Dorset seem analogous to those 

 which are found in Normandy, reposing on the similarly corroded surfaces of 

 the chalk, and which occur also on the surface of other formations in that 

 part of Prance, each formation respectively being often covered with a cap- 

 ping of loose angular fragments composed of the hardest materials of the sub- 

 jacent strata. According to M. de Caumont, a breccia allied to the plastic 

 clay formation, and composed of angular chalk flints imbedded in red clay, 

 occasionally attaining the thickness of 80 and 100 feet, occurs in the valley 

 of the Rille, and various adjacent parts of Normandy*. M. de Caumont 

 speaks of aU these breccias under the head of Diluvium, — falling into the same 

 common error with many other Continental geologists, of including under the 

 term Diluvium many pebble beds and breccias which belong to the tertiary, 

 and to older formations. 



Chalk. 



The lofty escarpment of chalk which bounds our field of observation on 

 the north, forms the margin of the chalk downs of the southern part of Dor- 

 setshire, and is the direct continuation of the south frontier of the great chalk 

 basin of Dorset and Hants. Along great part of this south frontier, from the 

 east extremity of the Isle of Wight to the west extremity of Purbeck, and 

 thence to the cliffs of White Nore, where we enter on its history, Mr. Web- 

 ster has shown its position to be sometimes absolutely vertical, but for the 

 most part dipping at a very high angle northwards towards the interior of the 

 basin f . This high inclination ceases a little east of the promontory of White 

 Nore, where the chalk suddenly sweeps round, and dips at an angle of a few 

 degrees only to the north-east. Along the range of its escarpment westward, for 

 nearly twenty miles from White Nore to its termination at Chilcomb Hill, on 

 the east of Bridport, the dip is almost constantly towards the north, at angles 

 varying from 10° to 40°. Its mean elevation along all this range may be taken 

 at about 500 feet. The base of this escarpment appears throughout to be 



* See sections and description in M. de Caumont's Essai sur la Topographic Giognostique 

 (III Calvados ; and De la Beche on the Geology of the North Coast of France, from Fecamp to 

 St. Vaast, in Geol. Trans. Second Series, vol. i. Part I. p. 73 — 89. 



f See Sir Henry Englefield's History of the Isle of Wight, Plate 50 ; and the Geological 

 Transactions, First Series, vol. ii. Plate XI. 



