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1919 
this is suggested by the absence of overlapping or any appearance 
of gradual passage from the Pleistocene to the Neolithic fauna — 
it is probable that other than climatic causes were in operation, 
of which the isolation of Britain from the Continent appears to 
be the most effective, indeed, restriction of the area of the 
unglaciated region would render it inadequate to provide food 
for the larger mammalia. The length of time represented 
by such a break would depend upon the existence of land 
connexion with the Continent and the reafforestation of 
Southern Britain. 
The elevation that continued into Neolithic times probably 
represents recovery from a depression that may have caused 
isolation, but any evidences of such a change are now covered 
by the sea. In referring to Scotland during the Mecklenburgian 
or fourth Glacial Epoch, Dr. James Geikie says: “The seas 
tenanted by an Arctic fauna then stood some 130 feet or there- 
abouts above the present level, while the lowlands were treeless 
tundras clothed with arctic plants” ( 60 , p. 270). “The 
succeeding Lov r er Turbarian Epoch (=Lower Azilian) was 
marked by depression, the British area being separated from the 
Continent ” ( 60 , p. 289). Dr. A. Strahan says that the Neolithic 
submergence of at least 50 or 60 feet “ appears to be the last 
of a series of oscillations w-hich have affected the southern portion 
of our Islands ” ( 175 , pp. 474, cii.). 
The soundings of the English Channel reveal the existence 
of a valley of depression (Admiralty Charts), and show that a 
considerable elevation of the area would now be necessary to 
unite England with the Continent, in spite of the shoaling in 
the Straits of Dover. A much knver sea level even than the 
present would therefore have been sufficient to prevent 
migration. If the earth movements that caused the late 
Pleistocene changes of level w T ere due to the imposition of 
the load of ice and its release, or if the level of the sea was raised 
by the flow of water from melting ice, the comparatively rapid 
final recession of the ice-sheets must have resulted in submer- 
gence of only a temporary character. 
Although the foregoing solution of the problem depends 
to some extent upon a chain of probabilities, it is submitted that 
