CONDITIONS OF CONTINENTAL ICE. 247 



The thickness of the sheet or sheets covering that 

 region would depend, as has been shown, upon the 

 area covered and the rate of snowfall, or, rather, the 

 rate at which the ice was being formed. The sheet, 

 as has also been shown, must have been thickest at 

 the centre or centres of dispersion — if there were 

 more than one — and thinnest at the edge. The 

 extent of area covered by ice on North -western 

 Europe must have been great ; so also must have 

 been the amount of snowfall. 



That such a condition as this, to which we are led 

 by theoretical considerations, did actually prevail 

 during the Glacial Epoch is now established by the 

 facts of observation. Norway we know was the 

 great centre of dispersion of the ice, and here it has 

 been found that the sheet attained its greatest thick- 

 ness. It has been shown by Mr. Amund Helland that 

 its thickness there was over a mile. Scotland was 

 also a subordinate centre of dispersion, and we know 

 that the ice moving off it was sufficient to prevent 

 that country from being overridden by the great mass 

 of ice flowing outwards in all directions from the 

 Scandinavian centre. It was sufficient, but little more ; 

 for the Scandinavian ice, filling the German Ocean and 

 passing over the Orkney and Shetland Islands, was so 

 powerful as to bend back the Scottish ice and force it 

 to turn round after it had entered the German Ocean, 

 and pass obliquely over the flat lands of Caithness. 

 It was also sufficient to fill the entire Baltic and to 

 pass over on Germany, down even to the foot of the 

 Saxon uplands. All this has now been completely 

 established by the observations of geologists. 



