ARCTIC ICE. 89 



against her sides ; and instances have been known wherein 

 a ship so circumstanced has been crushed hke an egg- 

 shell : or should her timbers be able to resist the terrible 

 force of these fragments, they will continue to pile over 

 one another like rocks, and finally either break or over- 

 whelm the vessel by their weight. In such case, all hands 

 must quit her, and provide for their safety as well as they 

 can. 



Another kind of ice remains for observation, in many 

 respects differing from the former, and which has long 

 engaged the attention of the naturalist ; that is, the ice 

 berg. From chemical experiments, it is well known that 

 the freezing process approximates to that of boiling in its 

 effects. The result in both is nearly ahke. For instance, 

 sea water boiled evaporates nearly free from the salts 

 which it is known to contain in combination. If the 

 vapour so raised be condensed, the quantity of water free 

 from salt is nearly two thirds of the whole. Repeated dis- 

 tillations will make the product more pure ; but this pro- 

 portion rudely taken is tolerably near the truth. Now it is 

 known also, by those who have had an opportunity of 

 ascertaining the fact, that about two thirds of the sub- 

 stance of the ice berg is fresh water. Ships going into 

 the Greenland seas and Davis's Straits in pursuit of the 

 whale, are accustomed to have on board only a supply of 



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