250 GEOLOGY OF THE ISLE OF WIGHT, 



estuary exactly in the position, which we should, by analogy with 

 the Thames, have ascribed to the ancient river Frome. 



Among the tributaries of this ancient Frome we may mention 

 on the north side the Stour, the Avon, the Anton, and the Itchin ; 

 on the south side, the small stream which traverses the Chalk 

 escarpment at Oorfe, the three rivers of the Isle of Wight, and in 

 all probability a tributary between the Needles and the coast of 

 Dorset, in the great gap now occupied by the sea. The northern 

 boundary of the basin of this old river can be traced without 

 difficulty, but of the southern boundary a very small portion only 

 is left. It runs south of Dorchester, across the Isle of Purbeck, 

 and reappears in the extreme south point of the Isle of Wight. 

 The valleys in the south side of Rew, Week, and Boniface Downs 

 are therefore almost the only survivors of another river system 

 next on the south to that of the Frome. 



This small portion of watershed does not follow the crest of 

 either the Brixton or Sandown anticline, but lies among the 

 Downs where a southerly and south-easterly dip has fairly set in. 

 An explanation of this fact would probably be forthcoming, could 

 we tell what was the form of the land which once lay to the south. 



