£82 GREENLAND OR POLAR ICE. 



portion to its depth under water ; light ice conse- 

 quently drives faster than heavy ice, and loose ice 

 than fields : loose ice meeting the side of a field 

 in its course, becomes deflected, and its re-action 

 causes a circular motion of the field. Fields may 

 approximate each other, from three causes : firsts 

 If the lighter ice be to windward, it will, of ne- 

 cessity, be impelled towards the heavier : second- 

 ly^ As the wind frequently commences blowing 

 on the windward side of the ice, and continues 

 several hours before it is felt a few^ miles distant 

 to leeward, the field begins to drift, before the 

 wind can produce any impression on ice, on its op- 

 posite side ; and, thirdly. Which is not an uncom- 

 mon case, by the two fields being impelled to- 

 wards each other, by winds acting on each from 

 opposite quarters. 



The closing of heavy ice, encircling a quantity 

 of bay ice, causes it to run together with such force, 

 that it overlaps wherever two sheets meet, until 

 it sometimes attains the thickness of many feet. 

 Drift-ice does not often coalesce with such ^ 

 pressure, as to endanger any ship, which may hap- 

 pen to be beset in it : when, however, land opposes 

 its drift, or the ship is a great distance immured 

 amongst it, the pressure is sometimes alarming^ 



Icebergs, 



The term icebergs has commonly been applied 

 to those immense bodies of ice, situated on the 



