1870. | BROWN—PHYSICS OF ARCTIC ICE. 699 
6. Inferences from the foregoing Fucts—I conceive that we are 
justified in concluding from the data which we at present possess 
that the following were the changes which Scotland underwent 
during the glacial epoch :— 
(a.) That after the Tertiary period the country was covered with 
a.great depth of snow and ice, very much as in Greenland at the 
present day; but possibly some of the mountain-tops appeared as 
islands. During this and the subsequent period glaciers ploughed 
their way down from the inland ice, and icebergs broke off and 
reached the sea through the glens, then ice-fjords. This glacier- 
covering must, to a considerable extent, have extinguished the pre- 
existing fauna and flora, though I do not agree with Mr. Jamieson 
that the flora and fauna were wholly extinguished. To this period 
we owe the “ till,” though I consider that this till was forming also 
during the subsequent period, and, in fact, as long as the country 
was swathed in ice and snow. All this period also the laminated 
clays were beginning to form from the clay-laden subglacial rivers. 
(G.) After this the country sank gradually, as Greenland is now 
sinking, to the depth of several hundred feet; and during this 
period most of the glacial laminated fossiliferous clays were formed. 
During this period boulders were deposited from the icebergs broken 
off from the glaciers of Scotland, as well as from the icebergs and 
other floating ice drifted both from the north and south, as was also 
the case during the former (@) period. I consider now that the greater 
portion of the boulders and other moraine was deposited from home 
bergs ; for the fact seems often to be lost sight of by some theorists 
that bergs broke off from glaciers of the country, as well as floated 
south from Scandinavia. What the extent of this submergence 
was is yet sub judice. The extent of submergence in Wales seems 
to have been 1800 feet or more; but in Scotland fossil shells of that 
period have never been found much above 500 feet, though Mr. 
Jamieson thinks he saw marine beds as high as 1500 feet. How- 
ever, until we have more positive evidence, we are justified in con- 
cluding that from 500 to 600 feet was the amount of subsidence. 
It is very suggestive that, on comparing Lyell’s Map of Britain sunk 
600 feet’, the very parts under the sea are almost identically those 
on which the greatest amount of fossiliferous Boulder-clay ws now 
ound. 
‘ (y.) The country seems then to have emerged from the water, 
but no doubt slowly, until the glaciers finally left the country, un- 
less, perhaps, as in Norway, in the mountains, though it appears 
that the rivers, from the melting of the ice and the glaciers them- 
selves, had disarranged the beds considerably, leaving behind them 
much débris of rocks &c.* 
1 « Antiquity of Man,’ p. 287, fig. 40. 
2 Hitherto this has been argued on hypothetical grounds ; but since this paper 
was written, in a memoir read before the Edinburgh Geological Society (May 6, 
1869, ‘Transactions,’ vol. i. p. 330, and ‘ Geol. Mag.’ vol. vii. p. 296), “On two 
River Channels buried under the drift,’ by Mr. James Croll, of the Geological 
Survey of Scotland, this rise has been lifted out of the range of hypothesis into 
