Physical Geography. 209 



however, be very erroneous. In the first place there is 

 no reason to believe that the outliers in Buckingham- 

 shire, near Aylesbury and Quainton, mark the original 

 limits of the Purbeck strata, for the whole country has 

 suffered so much by denudation, that we may be sure 

 that these beds originally spread further. Again, 

 on the south, the Wealden strata of the Isle of Wight 

 are thick, and dip northerly between Cowleaze Chine 

 and Compton Bay, and originally must have spread to 

 some unknown distance beyond the coast cliffs, and, 

 indeed, we may be sure that they now occupy part of 

 the bottom of the sea beyond the coast line. Crossing 

 the Straits of Dover to the Bas Boulonnais, we find the 

 Weald Clay much attenuated, but passing under the 

 Cretaceous strata for some unknown distance. Taking 

 all these points into account it would probably not be 

 too much to add one-half to the 20,000 square miles, as 

 being nearer the original area of the Delta, or 30,000 

 square miles in all. The area of the Delta of the 

 united great rivers of the Granges and Brahmaputra, 

 from the sea to the latitude of Rajmahal, is usually 

 estimated at about 40,000 square miles, and therefore 

 it would probably be under the mark to estimate the 

 size of our old river as being quite as large as the 

 largest of these great rivers of India. At the very 

 least it must have been as extensive as the Delta of the 

 Quorra in Africa, the area of which has been estimated 

 at 25,000 square miles. 



Facts such as these are sufficient to prove that 

 this ancient stream was, in its day, a first class conti- 

 nental river. Away to the west of a great plain, through 

 which it flowed, lay the granite hills of Devonshire, 

 separated by a broad flat valley from what are now the 

 mountains of Wales. The old Mendip Hills, which, as 



p 



