1916.] THE POST-GLACIAL ELEVATION. 395 



thickness, the bottom o£ which he did not reach. He 

 describes the peat to be yellow in colour and to have but 

 little recognisable vegetable structure, but still visibly a peat. 

 This deposit was associated with sea gravel which (to use his 

 own words) " exactly resembled that of Fermain Bay." The 

 deposit I have not seen, but I have no doubt that it is 

 correctly described by Mr. Mauger. 



This find has a distinct bearing on the deductions I have 

 drawn from other data. The sea gravel is a sea margin, and 

 the peat is evidently the remains of a marsh on the border of 

 the sea margin. The yellow colour, I believe, is due to the 

 infiltration of the yellow clay which has been deposited 

 over it. 



The yellow clay determines the period, and we may 

 therefore assign the deposit to Mousterian times and thus 

 obtain confirmation of the deposit of the clay by water and of 

 the post-Mousterian submergence. 



Stage 5. 

 THE POST-GLACIAL ELEVATION. 



From the time of the submergence which laid down the 

 upper glacial clay we have but one subsidence recorded on our 

 shores. That one belongs to a very recent period and must 

 be described as the last geological event of any importance, 

 therefore beyond this mention I leave it to a future chapter of 

 this paper. 



The land is now permanently above the sea-level, and as 

 the rise can only be proved by negative evidence it will be in 

 order for me to state the accepted facts which I cannot either 

 support nor contradict from geological data. There are, 

 however, means of judging of the application of the accepted 

 facts by their general agreement with our negative evidence. 



It is believed that the land rose to a height of at least 

 600 feet above the present sea-level, and in doing so caused 

 the channel to become dry land. Sea erosion then set in, and 

 the rivers which flowed down the channel and into the main 

 river (Hurd Deep) were gradually deepened and their beds 

 were cut to lower levels. After a long time a change set in 

 and the land sank again, but only to its present level or 

 near to it. 



Of all this we have only the evidence of our sunken 

 forests which grew at a level now covered by the sea, and grew 

 for a time sufficiently long to form peat beds 12 to 14 feet 

 thick as occur in all the islands. 



