33 
:879-] Relations to that of the Glacial Epoch. 
inental ice such a condition of things as this may appear 
ncredible ; but if the principles we have been considering 
ie correct , it follows as a necessary consequence. If, during 
he Glacial Epoch, the quantity of ice annually formed in 
'Jorth-western Europe was much in excess of the quantity 
nelted, enormous ice-sheets must of necessity have been 
ormed. 
The thickness of the sheet or sheets covering that region 
irould depend, as has been shown, upon the area covered and 
he rate of snowfall, or, rather, the rate at which the ice was 
ieing formed. The sheet, as has also been shown, must 
ave been thickest at the centre or centres of dispersion — if 
here were more than one — and thinnest at the edge. The 
xtent of area covered by ice on North-Western Europe 
lust have been great ; so also must have been the amount 
f snowfall. If we assume that the Glacial epoch was due 
o an increase in the eccentricity of the earth’s orbit, it 
dIIows that the amount of snowfall on the ice-sheet, during 
ummer at least, must have been excessive. Owing to the 
earness of the sun in perihelion at that season, the amount 
f evaporation in the Atlantic would be greater than at 
resent. The aqueous vapour thus raised would be carried 
orth-eastward by the south-west winds, which would then 
—for reasons which have been stated at length elsewhere — be 
luch stronger than they are at present. The vapour on reaching 
he ice-sheet would be condensed by the cold, and fall as snow. 
)wing to the rapid accumulation of the ice over so large an 
rea, and the consequent difficulty in getting rid of it, a con- 
ition of things similar to that which now obtains in the 
mtarCtic regions would ere long result. 
That such a condition as this, to which we are led by 
heoretical considerations, did actually prevail during the 
ilacial epoch is now established by the faCts of observation. 
Norway we know was the great centre of dispersion of the 
:e, and here it has been found that the sheet attained its 
reatest thickness. It has been shown by Mr. Amund 
lelland that its thickness there was over a mile. Scotland 
ras also a subordinate centre of dispersion, and we know 
iiat the ice moving off it was sufficient to prevent that 
ountry from being overridden by the great mass of ice 
owing outwards in all directions from the Scandinavian 
entre. It was sufficient, but little more, for the Scandina- 
ian ice filling the German Ocean, and passing over the 
Orkney and Shetland Islands, was so powerful as to bend 
ack the Scottish ice, and force it to turn round, after it had 
VOL. ix. (n.s.) 
D 
