THK WORLD'S WONDERS. <![)<) 



deep, which, melting during the summer, forms small ponds or 

 lakes upon their surface. 



Frequently ice-fields are whirled about in a rotary motion, 

 which causes their circumference to gyrate with a velocity of 

 several miles per hour. When a field, thus sweeping through the 

 waters, comes into collision with another which may possibly be 

 revolving with equal rapidity in an opposite direction when 

 masses often twenty or thirty miles in diameter, and each weigh- 

 ing many millions of. tons, clash together imagination can hardly 

 conceive a more appalling scene. The whalers at all times require 

 unremitting vigilance to secure their safety, but scarcely in any 

 situation so much as when navigating amidst these fields, which 

 are more particularly dangerous in foggy weather, as their 

 motions cannot then be distinctly observed. No wonder that 

 since the establishment of the fishery numbers of vessels have 

 been crushed to pieces between two fields in motion, for the 

 strongest ship ever built must needs be utterly unable to resist 

 their power. Some have been uplifted and thrown upon the ice ; 

 some have had their hulls completely torn open ; and others have 

 been over-run by the ice, and buried beneath the fragments piled 

 upon their wreck. 



The icebergs, which, as their name indicates, rise above the 

 water to a much more considerable height than the ice-fields, 

 have a very different origin, as they are not formed in the sea 

 itself, but by the glaciers of the northern highlands. As our 

 rivers are continually pouring their streams into the ocean, so 

 many of the glaciers or ice-rivers of the Arctic zone, descending 

 to the water-edge, are slowly but constantly forcing themselves 

 farther and farther into the sea. In the summer season, when 

 the ice is particularly fragile, the force of cohesion is often over- 

 come by the weight of the prodigious masses that overhang the 

 sea or have been undermined by its waters ; and in the winter, 

 when the air is probably 40 or 50 below zero, and the sea from 

 28 to 30 above, the unequal expansion of those parts of the 

 mass exposed to so great a difference of temperature cannot fail 

 to produce the separation of large portions. This is the gener- 



