BRITISH POSTGLACIAL &> RECENT DEPOSITS. 437 



1st, That the lower forest-bed points to a former wider 

 extent of land and a climate capable of nourishing and sustain- 

 ing an abundant forest-vegetation. 



2d, That the peat, underneath which these trees He buried, 

 indicates more humid conditions, which brought about the 

 decay and overthrow of the forests, and fostered an abundant 

 growth of marsh-plants. 



3d, That the wide peat-covered plains eventually sank under 

 the sea to a depth below its present level of 25 feet or there- 

 about. Neolithic man was at this time an occupant of the 

 land. 



4th, That by and by the sea again slowly retreated, and 

 wide freshwater lakes made their appearance. 



5th, That the upper forest -bed points to a recurrence of 

 genial climatic conditions probably similar to those underneath 

 which the trees of the lower forest-bed flourished ; and that the 

 land at this time was more extensive than it is now. 



6th, That the upper peat implies more humid conditions, 

 adverse to the growth of great forests but favourable to that of 

 marsh-plants. 



7th, That the beds above the peat indicate a recent encroach- 

 ment of the sea — an encroachment which had probably com- 

 menced before the destruction of the forests was completed. 



We may now take a glance at the Postglacial and Eecent 

 deposits of the Cornish coast. The only accumulations in 

 Cornwall which can be recognised as pertaining to the Ice Age 

 are certain raised -beaches and the peculiar earthy and stony 

 ddbris (" head ") which caps them. These, as we have seen, 

 belong probably to the last interglacial epoch and the final cold 

 stage of the Glacial Period, and we have next to inquire what 

 were the physical and climatic conditions that obtained in 

 Cornwall subsequent to the accumulation of the well-known 

 " head," and the formation of the coarse gravels and stones of 

 the famous stream-tin deposits. The nature of these deposits is 

 revealed to us by the numerous sections which have been made 

 in the search for tin, and there is certainly a marked similarity 



