Ch. XVI.] 



ICEBEEGS. 



381 



base of a lofty precipice, the sheet of ice is prevented from 



Neve 



theless, it often continues on shore at the foot of the cliff, and 

 receives accessions of drift snow blown from the land. Under 

 the weight of this snow the ice sinks slowly if the water be 

 deep, and the snow is generally converted into ice by partial 

 liqnefaction and re-congelation. In this manner, islands of 

 ice, of great thickness and many leagues in length, originate, 

 and are eventually blown out to sea by off-shore winds. Tn 

 their interior are enclosed many fragments of stone which 



Fig. 25. 



Iceberg seen 1,400 miles E.N.E. of Enderby's Land. 



Sketched by Mr John M'Nab* 



them 



formation. 



> common 

 melt in la 



moderate 



surface water and the air. Hence their centre of gravity 

 changes continually, and they turn over and assume very irre- 

 gular shapes. 



In a voyage of discovery made in the antarctic regions 

 m 1839, a dark-coloured angular 



mass 



seen 



* Journ. of Roy. Geograph. Soc. vol. ix. p. 526. 



