112 ME. A. J. JTTKES-BKOWNE ON THE AGE AND [May I907, 



In the second place, the broken and fragmentary state of the 

 plateau, the rounded edges which border many of the isolated parts 

 of it, and the numerous deeply-cut valleys by which it is traversed, 

 prove that it has been subjected to the erosive action of rain and 

 rivers for a long period of time. Its dissection into separate hills 

 and plateaus can hardly have been effected within the limits of 

 Pleistocene time ; and there are good reasons for thinking that the 

 present system of watercourses could not have been established on 

 its surface, but must have originated on the surface of other beds 

 which covered it to a considerable thickness. 



We have, therefore, to consider whether this plateau may not 

 date back to Mesozoic or early Tertiary times, and whether it may 

 not have been buried beneath a certain thickness of Cretaceous or 

 Eocene deposits, or both, to be denuded of this covering and 

 revealed during the progress of later Tertiary time. 



The structure of the country which extends from the Haldon 

 Hills through the east of Devon furnishes us with evidence of 

 two epochs, during which such a plain might have been formed. 

 These are the early part of the Cretaceous Period and the early 

 part of Eocene time. 



At the beginning of the Cretaceous Period the greater portion of 

 England and Wales was land, and it was only in consequence of 

 continued subsidence that the Cretaceous sea gradually spread 

 eastward, and by its advance formed a plane of marine erosion 

 across the basset-edges of the older rocks, passing from the surface 

 of the Upper Oolites in Dorset to that of the Trias and Permian 

 in Devon. 



The Cretaceous sands lie upon the Permian conglomerates through- 

 out the whole area of the Haldon Hills, and there is no reason to 

 suppose that the Cretaceous planation cut down to any lower 

 formation along the same line of longitude in Devon. South of the 

 Teign estuary we find a large area of Permian conglomerate, the 

 base of which nowhere rises much above sea-level, while its surface 

 reaches to heights of over 500 feet, yet no trace of Cretaceous sand 

 in situ has been observed upon it. These sands did, no doubt, 

 originally extend over the entire area between the Haldon Hills and 

 the shores of Torbay, but in all probability at a high relative level 

 above the present surface of the ground, with always a considerable 

 thickness of Permian deposits between them and the older Palaeozoic 

 rocks. 



The next period at which extensive planation took place in 

 Devon is that of the Eocene. Throughout the eastern part of East 

 Devon this plane probably lay principally upon the Chalk, but west 

 of Honiton and Sidmouth it seems to have passed on to the surface 

 of the Greensand. Mr. Clement Reid has expressed the opinion 

 that the deep gravel which caps the Haldon Hills is Eocene, and of 

 the same date as the Bagshot gravels of Dorset. It is true that he 

 regarded them both as river-gravels, but their mode of occurrence 

 on Haldon as a plateau-gravel seems to me sufficient to make such 

 a view of their origin almost impossible, seeing that they extend 



