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 Spitzbergen are 
filled up with solid ice, which has been accumulating 
for uncounted ages; these are the sources from 
whence the floating icebergs are supplied. Perhaps 
as long ago 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. 
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: 
