122 Henry Bury — Escarpments and Transverse Rivers. 



and formed the bottom of a shallow sea, which passed through the 

 gaps, breaking the Chalk escarpment up into a series of islands." 



No evidence is offered that the sea ever reached the foot of the 

 escarpment at all ; and even if such evidence were produced, we 

 should still ask for proof that it was the sea which formed the gaps, 

 and not the ga23s (as drowned river valleys) which admitted the 

 sea. But it is as an explanation of the transference of quartz pebbles 

 from the Lower Greensand to the Chalk that the hypothesis seems 

 to have been framed, and here the interpolation of a narrow arm of 

 the sea between the two lines of strata would seem to be rather 

 a hindrance than a help to such migration, and it is submitted that 

 unless very strong reasons against it can be given, the hypothesis 

 of transference by transverse rivers is both simpler and more efficient. 

 No less unsatisfactory is the account given of the origin of the 

 transverse rivers themselves. We are told that ' "When the elevation 

 above sea-level "(of the sea-bottom in the Gault)" took place . . . local 

 streams would tend to form, flowing through all the gaps ". But 

 this is by no means obvious. It has been held that the absence of 

 longitudinal rivers running directly to the sea from the Weald is 

 evidence against the marine origin of the escarpments and river 

 system of that region ; and similarly here we might expect that, 

 if the sea entered from the east along the lines of weak strata, 

 it would retreat in the same direction, thereby giving rise at once to 

 a longitudinal drainage. 



It must not be supposed that a subaerial origin for the windgaps 

 is inconsistent with any influence of the "sea in determining the 

 drainage system of the South-East of England. On the contrary, it 

 leaves untouched the question whether that system originated on 

 an uplifted marine plain ; and it is by no means opposed to the 

 possibility that the sea, which seems at one time to have filled the 

 London Basin, may, during periods of temporary dej)ression, have 

 made its way along the foot of the escarpments, as it seems to have 

 done through the drowned valleys of the South Downs in Pleistocene 

 times. 



Nor must I be thought to wish in any way to depreciate the value 

 of Mr. Barrow's work. It is only to some of his theoretical views 

 that I take exception, because they appear to me retrogressive 

 and unsupjDorted by the facts so far before us. If there are other 

 facts necessitating a radical change of view, it is to be hoped that they 

 will soon be published. 



1 Op. cit., p. 40^ 



