BRITISH POSTGLACIAL 6- RECENT DEPOSITS. 435 



The trees which it contains are in many cases rooted in the 

 underlying boulder-clay, so that there can be no doubt that they 

 actually grew in situ. They consist of the usual species — oak, 

 pine, hazel, etc. Some of the flint weapons in the Liverpool 

 Museum are believed to have been derived from this peat-bed, 

 and it is said by Mr. Ecroyd Smith to have yielded bones of the 

 urus and great Irish deer, but Mr. de Eance doubts whether 

 this is the case, and is of opinion that neither animal remains 

 nor any trace of man or his works have yet been discovered in 

 this oldest member of the postglacial series. 



The sand (No. 5) occurs chiefly in the form of sand-hills 

 along the eastern or inner margin of the great plains, but is 

 continued underneath the overlying deposits to the west. It is 

 believed by Mr. de Eance to have been formed by the action of 

 the sea and wind at a time when the land stood at a relatively 

 lower elevation than the present, and the coast corresponded 

 pretty closely with what is now the 25-feet contour-line. The 

 sand was then spread out partly in shallow water and partly 

 upon the beach, and was blown inland so as to form a series of 

 dunes corresponding in character to the sand-hills which fringe 

 the modern coast. They tell us, then, of a time when the land, 

 which, during the growth of the lower buried forest, must have 

 extended much farther out to sea than it now does, gradually 

 became submerged to a depth below its present level of some 

 25 feet or thereabout. Before this submergence was fully 

 accomplished the trees had succumbed to the influence of 

 increasing moisture — marshes gradually extended their bounds, 

 and wide stretches of peat ere long occupied the site of the 

 ancient forest. By and by the sea itself invaded the broad flats, 

 here sweeping away the peat and prostrate timber, and there 

 covering it up with sand and silt and clay (No. 4). At the 

 same time the submerged portions of the river-valleys were 

 filled up and levelled with the floor of the sea. After these 

 conditions had obtained for some time the shallowing sea was 

 here and there excluded from the mud -flats, and wide lakes 

 of fresh water were formed. In these lakes gray silts were 



