232 SCANDINAVIA ONCE ENCRUSTED CHAP. xiu. 



trict, and is very commonly from north to south, or if it be 

 twenty or thirty or more degrees to the east or west of north, 

 still always corresponds to the direction in which the large 

 angular and rounded stones have travelled. These stones 

 themselves also are often furrowed and scratched on more 

 than one side, like those already spoken of as occurring in 

 the glacial drift of Bedford (p. 165), and in that of Norfolk 

 (pp. 213 and 218). 



When we contemplate the area which is now exposed to 

 the abrading action of ice, or which is the receptacle of mo 

 raine matter thrown down from melting glaciers or bergs, we 

 at once perceive that the submarine area is the most exten 

 sive of the two. The number of large icebergs which float 

 annually to great distances in the northern and southern 

 hemisphere is extremely great, and the quantity of stone 

 and mud which they carry about with them enormous. Some 

 floating islands of ice have been met with from two to five 

 miles in length, and from one hundred to two hundred and 

 twenty-five feet in height above water, the submerged por 

 tion, according to the weight of ice relatively to sea water, 

 being from six to eight times more considerable than the part 

 which is visible. Such masses, when they run aground on 

 the bottom of the sea, must exert a prodigious mechanical 

 power, and may polish and groove the subjacent rocks after 

 the manner of glaciers on the land. Hence there will often 

 be no small difficulty in distinguishing between the effects of 

 the submarine and supramarine agency of ice. 



Scandinavia once covered with Ice, and a Centre of 

 Dispersion of Erratics. 



In the north of Europe, along the borders of the Baltic, 

 where the boulder formation is continuous for hundreds of 

 miles east and west, it has been long known that the erratic 



