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highest have to be depressed the lowest to resume their original 
relative position, and that there is plenty of evidence of suc- 
cessive movements of elevation along the same axes, — along 
the Pyrenees, for instance, and along the area we have now 
to do with, viz., Wales and North-Western England; so we 
need not at all assume a uniform elevation or depression over 
the whole of Britain at the same time. 
We start then with this. There was a time when the moun- 
tains which run down through Scandinavia, Scotland, the north 
of England, and through Wales, were so high that icefields 
and glaciers prevailed along the whole range. Now we must 
refer to a few figures. If an elevation of a little over 2,000 feet 
extended over an area so wide as to take in some of the borders' 
of the Atlantic to 300 or 400 miles beyond the coast of Ireland, 
where the sea bottom runs down from 2,130 to 10,700 feet in 
about 15 sea-miles, and it were all uplifted, we should have land 
all over from the Continent 400 miles out into the Atlantic 
beyond the coast of Ireland. The mountain ranges would be so 
much further from the sea, and the climate be less insular and 
less equable. The deep valley running down where now we 
have the Baltic Sea would bring glacier ice from Scandinavian 
fields; and from the Norway coast, probably, other ice would 
creep south. But we need not assume a uniform elevation. 
Probably, the amount of elevation was highest in the mountains, 
and at first, when Scandinavian ice predominated, it overrode 
the Scotch mountains. Scotch glacialists tell us they have 
evidence of this. Precipitation being equal, the more northern 
colder regions generated more ice, even if the mountains were 
not higher. So, from the mountains of Scotland, ice pressed the 
Lake District, from which, again, the ice held back the glaciers 
from the North Welsh heights, and turned them to the East. 
But when submergence followed, the Scandinavian ice 
stopped short of Scotland; and so in turn each more southern 
group of hills was freed to distribute its own ice all round as 
the ground fell easiest for it. 
This is the commencement of the period with which for our 
inquiry we have most to do. What kind of country was here 
before the Glacial Period we have not much to tell. A few 
marine deposits on our eastern coast tell what the creatures 
were that swam the seas some time before, but of the plants 
and animals upon our hills and plains we know but little. 
After the period of extreme glacial conditions the land went 
down, and warm currents from the south and west approached 
the hills. We cannot suppose that all the forms of northern 
life were driven back at once, but by degrees they all retreated 
