176 



ISLAND LIFE 



PART I 



in arms of the sea, or of the terminal face of the ice-sheet 

 which passes beyond the land into the ocean. In both 

 these cases abundance of rocks and dShris, such as form the 

 terminal moraines of glaciers on land, are carried out to 

 sea and deposited over the sea-bottom of the area occupied 

 by icebergs. In the case of an ice-sheet it is almost certain 

 that much of the ground-moraine, consisting of mud and 

 imbedded stones, similar to that which forms the " till " 

 when deposited on land, will be carried out to sea with the 

 ice and form a deposit of marine " till " near the shore. 



It has indeed been objected that when an ice-sheet 

 covered an entire country there would be no moraines, and 

 that rocks or dShris are very rarely seen on icebergs. 

 But during every glacial epoch there will be a southern 

 limit to the glaciated area, and everywhere near this limit 

 the mountain-tops will rise far above the ice and deposit 

 on it great masses of cUhris ; and as the ice-sheet spreads, 

 and again as it passes away, this moraine-forming area 

 will successively occup}' the whole country. But even 

 such an ice-clad country as Greenland is now known to 

 have protruding peaks and rocky masses which give rise 

 to moraines on its surface ; ^ and, as rocks from Cumberland 

 and Ireland were carried by the ice-sheet to the Isle of 

 Man, there must have been a very long period during 

 which the ice-sheets of Britain and Ireland terminated in 

 the ocean and sent off abundance of rock-laden bergs into 

 the surrounding seas ; and the same thing must have 

 occurred along all the coasts of Northern Europe and 

 Eastern America. 



We cannot therefore doubt that throughout the greater 

 part of the duration of a glacial epoch the seas adjacent to 

 the glaciated countries would receive continual deposits of 

 large rocks, rock-fragments, and gravel, similar to the 

 material of modern and ancient moraines, and analogous 

 to the drift and the numerous travelled blocks which the 

 ice has undoubtedly scattered broadcast over every glaciated 

 country ; and these rocks and boulders would be imbedded 

 in whatever deposits were then forming, either from the 

 matter carried down by rivers or from the mud ground off 

 1 Nature, Vol. XXL, p. 345, "The Interior of Greenland. " 



