46 THE POLAR WORLD. 



which are the cause of so much delay and danger. They are icebergs when they 

 tower to a considerable height above the waters, and ice-fields when they have a 

 vast horizontal extension. A floe is a detached portion of a field ; pack-ice, a 

 large area of floes or smaller fragments closely driven together so as to oppose a 

 firm barrier to the progress of a ship ; and drift-ice, loose ice in motion, but not 

 so firmly packed as to prevent a vessel from making her way through its yield- 

 ing masses. 



The large ice-fields which the whaler encounters in Baffin's Bay, or on the 

 seas between Spitzbergen and Greenland, constitute one of the marvels of the 

 deep. There is a solemn grandeur in the slow majestic motion with which 

 they are drifted by the currents to the south ; and their enormous masses, as 

 mile after mile comes floating by, impress the spectator with the idea of a 

 boundless extent and an irresistible jDow^er. But, vast and mighty as they are, 

 they are unable to withstand the elements combined for their destruction, and 

 their apparently triumphal march leads them only to their ruin. 



When they first descend from their northern strongholds, the ice of which 

 they are composed is of the average thickness of from ten to fifteen feet, and 

 their surface is sometimes tolerably smooth and even, but in general it is cov- 

 ered with numberless ice-blocks or hummocks piled upon each other in wild con- 



AMONG HUMMOCKS. 



fusion to a height of forty or fifty feet, the result of repeated collisions before 

 flakes and floes were soldered into fields. Before the end of June they are cov- 

 ered with snow, sometimes six feet deep, wdiich melting during the summer 

 forms small ponds or lakes upon their surface. 



