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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 22, 



of Mactra, Tellina, and Cctrdium found at Alphington. To the west, 

 the uppermost portions of the valley accumulations of Cornwall, as 

 those of Pentuan (Section No. 1. PI. VI.), belong to this level (De la 

 Beche, Report on Devon and Cornwall, p. 401). Without multiplying 

 instances, many of which will readily occur to most geologists, evi- 

 dence of a like change of level can be traced up Channel, as far east- 

 ward as the valley of the Ouse in Sussex, where the former spread of 

 the waters of the sea, over the low tract about Lewes, was long since 

 pointed out by Dr. Mantell : here too the amount of elevation most 

 closely corresponds with that on the west. 



The level of many accumulations of sand and shingle, at small 

 heights above the reach of the sea, would also refer them to this last 

 change of relative position. Of these we may notice those of the low 

 ground east of Cherbourg, and those along the west coast of the 

 Cotentin ; like beds may be seen around the Channel Islands, such 

 as those from St. Helier's towards Mont Orgueil, and in Guernsey, 

 particularly about the north end of the island. 



Fig. 2. — Section at St. Sampson's, Guernsey. 



d 



a. Granite. 



b. Surface of the underlying rock covered by rounded pebbles of granite. 



c. Granitic sand with large angular fragments of granite. 



d. Sea-sand with pebbles. 



e. Horizontal layers of sand. 



Fig. 2 was taken from a section of superficial accumulations exposed 

 in St. Sampson's parish : the upper surface of the granite is very un- 

 even ; upon it are rounded boulders of granite, covered by a consi- 

 derable thickness of granitic sand, containing large angular fragments 

 of granite ; above this is pure sea-sand and pebbles, with one principal 

 seam of shingle, the whole so far conforming to the outline of the 

 subjacent rock : the uppermost layers of sand are horizontal and have 

 cut across the lines of deposition of the lower portion of the mass, the 

 result of the movements of the water, under less depths than those at 

 which the sands were accumulated. 



In the construction of the sea-wall from Tor Abbey towards Paign- 

 ton, beds of Sabellaria were cut through at about high-water line ; the 

 upper limit of these animals is below that of mean sea-level ; these 

 beds would thus indicate a rise of at least half the amount of the tide 

 at this place. 



These former upper tidal zones, with their corresponding raised 

 marine and estuary beds, are the only portions of those indications of 



