THE SUB-OCEANIC DEPRESSION, ETC. 425 
this region, having little variation of elevation of surface, 
is one well defined physical area with higher lands on 
the north and east and the Pyrenees on the south, and 
open only to the sea on the west. This great area, con- 
sequently, under glacial conditions must have been covered 
by an ice-sheet, or vast glacier, moving constantly westwards, 
and as constantly giving off portions of itself to the sea 
where is now the Bay of Biscay. 
The discharge of glacial ice from the southern part of the 
west coast of France would consequently be of vastly greater 
amount and erosive power than any discharge of land ice 
from the parts of the coast farther north, where neither 
the physical features of the interior land nor the climatal 
conditions would be nearly so favourable for the production 
ot vast masses of moving ice descending to the sea along 
a restricted coast-line. As this constant discharge of glacial 
ice would powerfully erode and cut back the land, the sea 
cliffs would here be more rapidly cut back than farther 
north, and the coast-line would consequently recede and 
form a broad indentation. The great width of the sub- 
merged Continental Platform at the north of the Bay of 
Biscay, from 100 to 200 miles, and its comparative narrow- 
ness off the southern part of its eastern coast, corresponds in 
a remarkable manner with what might be expected to result 
from such localized intensity of erosive action. 
Simultaneously with the great erosion by the glacial ice 
from the northern side of the Pyrenees there would be 
erosive action going on from the movement and discharge of 
the glacial ice produced on the southern side of the western 
end of the range. This would be by no means small. The 
district that now forms the north-western part of the 
Spanish province of Navarra and the whole of Guipuscoa 
consists of mountains rising to 3,000 or 4,000 feet above the 
sea-level, separated by deep valleys. These valleys when 
elevated above the snow-line would be eminently adapted to 
hold snow and form large glaciers. One of these, the 
valley of the River Bidassoa, runs far up into the mountains, 
and bifurcates and ramifies into deep and spacious subsidiary 
valleys that are quite ideal receptacles for the accumulation 
of vast masses of snow. This extensive valley, or rather 
system of valleys, opens out at its seaward termination in 
the very bight of the Bay of Biscay, and but little to the 
south of the Fosse de Cap Breton. 
And along the whole of the south side of the Bay of 
