48 



THE POLAE WORLD. 



FORMS OF ICEBERGS. 



be utterly unable to resist their power. 



which may posaibly be revolving >vith equal rapidity in an opposite direction 

 — when masses not seldom twenty or thirty miles in diamater, and each weigh- 

 ing many millions of tons, clash to- 

 gether, imagination can hardly con- 

 ceive a more appalling scene. The 

 whalers at all times require unremit- 

 ting 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 can not then be distinctly ob- 

 served. No wonder that since the 

 establishment of the fishery numbers 

 of vessels have been crushed to pieces 

 between two fields in i^jotion, for the 

 strongest ship ever built must needs 

 Some have been ujilifted and thrown 

 upon the ice ; some have had their hulls completely torn open ; and others 

 have been overrun by the ice, and buried beneath the fragments piled upon 

 their wreck. 



The icebei'gs, which, as their name , 



indicates, rise above the water to a J7^ 3-r"-.— ==_ . 



much more considerable height than 



the ice-fields, have a very different or- ^ 



igin, as they are not formed in the J^ 



sea itself, but by the glaciers of the 

 northern highlands. As our rivers 



are continually i:)Ouring their streams " ,^, ?:^ 



into the ocean, so many of the gla- "- 



ciers or ice-rivers of the Arctic zone, -_ ^ 



descending to the water-edge, are 

 sloAvly but constantly forcing them- 

 selves farther and farther into the 



sea. In the summer season, when ^ -^ ^ 



the ice is particularly fragile, the 

 force of cohesion is often overcome 

 by the weight of the prodigious mass- 

 es 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 expan- 

 sion of those i:)arts of the mass ex- 

 posed to so great a difference of temperature can not fail to produce tlie sep- 

 aration of large portions. 



m 



FORMS OF ICEBERGS. 



