Iviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



considered that his former observations on the bed of the English 

 Channel had prepared the way for the hypothesis he now advanced, 

 viz. the former existence of a land barrier composed of crystalline and 

 palaeozoic rocks, crossing from Brittany to the south-east of England, 

 and forming a gulf or bay open to the west. Into this bay the 

 marine fauna represented by the Pholades and their associates ex- 

 tended from the westward, and in the hollow of the bay at a some- 

 what later period, coast-ice brought the boulders from along the old 

 shore-line, which is now represented by a sunken peak in mid- 

 channel lying south-east from the Isle of Wight, and by a shoal of 

 granitic detritus. The author also alluded to the alterations of level 

 which had subsequently taken place, and the partial destruction of some 

 and formation of other deposits by frequent oscillations. That these 

 huge boulders of crystalline and other older rocks, some of which are 

 more than 20 feet in circumference, have been transported by ice, seems 

 probable enough, but there appears to me a physical difficulty in the 

 way of Mr. God win- Austen's theory, that they were stranded in the 

 hollow of this supposed bay. Icebergs or coast-ice charged with such 

 boulders are uniformly moved by currents; and, if this bay were closed 

 up to the eastward, it is difficult to imagine how any current would 

 so set directly into the bay as to strand the floating icebergs in the 

 bight. The same current which brought them in, supposing a 

 current to have set into the bay, would, by sweeping round the coast, 

 have again carried them out to sea ; at the same time, the occurrence 

 of these boulders in the drift-beds is of great interest ; but, without a 

 more careful comparison of the crystalline rocks on the opposite coast 

 and in the Chaimel Islands, it would be difficult to decide from whence 

 they may have been brought. It seems probable, however, that the 

 parent rocks will be found in the Channel Islands, or the numerous 

 reefs by which those islands are surrounded. 



Mr. Martin, in his paper on some geological features of the country 

 between the South Downs and the Sussex Coast, refers the boulder- 

 drift of Mr. Godwin-iVusten to another zone of Wealden drift in 

 addition to those which he had already described as mantling round 

 the nucleus of the Weald, the corresponding parts of which zone he 

 thinks are to be found in the Valley of the Thames. This zone he 

 considers as the remains of the boulder-deposit spread over the 

 tertiary districts of this and the adjoining parts of the North of 

 Europe, before their continuity was disturbed by the upheaval of 

 the great anticlinal axis of the South of England. Mr. Martin 

 regards the country under review as a sectional part of this great 

 anticlinal, and thinks that it must not be considered apart from 

 the wide geological area to which it belongs, and that its phsenomena 

 of arrangement and drift belong to the epoch of that upheaval, thus 

 showing the effect of powerful diluvial currents set in motion and 

 assisted at the same time by the dislocations known to abound in this 

 part of our island, and without the aid of which the author considers 

 we can arrive at no satisfactory conclusion respecting the drifts and 

 other phaenomena of the denudations and other surface-changes here 

 exhibited. 



