THE ARCTIC SEAS. 123 



of the air in their immediate neighbourhood, the 

 moisture of the atmosphere is condensed around 

 them; and hence they are often enveloped in fogs, 

 so as to be invisible within the length of a few 

 fathoms. A momentary relaxation of vigilance on 

 the part of the mariner, may bring the ship's bows 

 on the submerged part of an iceberg, whose sharp 

 needle-like points, hard as rock, instantly pierce the 

 planking, and perhaps open a fatal leak. Many 

 lamentable shipwrecks have resulted from this cause. 

 In the long heavy swell, so common in the open sea, 

 the peril of floating ice is greatly increased, as the 

 huge angular masses are rolled and ground against 

 each other with a force that nothing can resist. 



These ice-islands are quite distinct in their nature 

 from the field-ice, which so largely overspreads the 

 surface of the sea, and are believed to be entirely of 

 land formation, consisting of fresh water frozen. 

 The process of their formation is interesting: the 

 glens and valleys in the islands of Spitsbergen are 

 filled up with solid ice, which has been accumulating 

 for uncounted aees; these are the sources from 

 whence the floating icebergs are supplied. Perhaps 

 as Ions; asro as the creation of man, or at least as the 

 deluge, these glaciers began in the snows of winter ; 

 the summer sun melted the surface of this snow, and 

 the water thus produced, sinking down into that 

 which remained, saturated it and increased its density. 



7 J 



The ensuing winter froze this into a mass of porous 

 ice, and superadded a fresh surface of snow. The 

 same process again going on in summer, of water 

 percolating through the porous crystals, which in its 



