South-western Coal District of England. 307 



for the construction of Wells cathedral, Glastonbury abbey, and most of the 

 churches in that neighbourhood. 



The geographical extent of this formation is fully indicated in the Map. 

 Its general boundary is formed by an abrupt escarpment, fronting the north- 

 west, the lower regions of which consist of lias and lias-marl, while the oolite 

 forms the elevated table-land on its summit. After the principal ridges of 

 mountain limestone and old red sandstone, this table-land constitutes the 

 highest ground within our district, attaining near the north-eastern corner of 

 our Map the height of 1000 feet. It is indented near its edges by deep valleys, 

 which often completely surround and insulate extensive portions of it; and 

 even at a considerable distance from the general boundary of the oolite, 

 detached hummocks or outliers of it form abrupt, crested, and conical summits, 

 crowning platforms of lias. Good examples of these outliers are seen in the 

 long ridge of Dundry, which rises 700 feet above the sea, and in the neigh- 

 bouring hill of Stantonbury of equal height*. For the inferences to be drawn 

 in support of the diluvian theory from the facts here stated respecting the 

 physical structure of the hills of lias and oolite, and of the valleys which inter- 

 sect them, we refer to the memoir of Mr. Buckland at page 95 of the present 

 volume. 



Chapter V.— ON THE DILUVIAL AND ALLUVIAL DEPOSITS. 



] . On the diluvial deposits. 



The accumulations of diluvial debris in our district are not very striking 

 or extensive. The valley of the Severn seems to have formed their great 

 receptacle, and it is probable also that the extensive marsh-lands to the south 

 of the Mendips conceal deposits of the same kind. The vale of the Avon 

 exhibits beds of gravel on the south of Bath at Bath-hampton and Bath-wick, 

 and to the west of Bath at Twiverton, Newton, Bitton, and Keynsham. Near 

 the mouth of the Avon we find rolled fragments of all the rocks in the vicinity, 

 from the old red sandstone to the chalk, forming considerable heaps, though 

 covered by peat at the surface. These deposits in the vale of the Avon con- 

 tain the remains of the quadrupeds peculiar to diluvian beds, the bones of the 



* Dundry and Stantonbury hills have been chosen, on account of their natural strength, to 

 form part of the ancient fortified boundary of Wansdyke. Their summits have been strengthened 

 by large entrenched camps. This line of entrenchments ranges over Claverton and Farley downs, 

 and is now mentioned only as deriving its strength from the physical characters of the surface. To 

 the south of these hills a group of small similar outliers are scattered over the elevated lias plains 

 on the north of Timsbury, among which the Barrow hills may be distinguished by their singular tri- 

 cuspidated form. 



