1^,6 SEA AND LAND 



prisoned squadrons of bergs from the several glaciers which 

 have accumulated in the sea during the enduring frost, pour 

 forth into tlie more southern part of the ocean. Then they 

 become separated — the bergs impelled by the deeper cur- 

 rent set forth upon their long cruise toward the mid-Atlantic, 

 while th(^ floes follow the surface stream adown the coast of 

 Labrador ; the former to wander, it may be, for years ; the 

 latter to vanish in the heat of a single summer. 



In the process of destruction which a berg goes through, 

 its decay is aided by the frequent overturns to wliich it is sub- 

 jected. All the ice of the glacial streams, unlike that made 

 in the ordinary way, is moulded into shape under the great 

 strains to which it is subjected in its journey over the surface 

 of the earth. These strains are not all productive of move- 

 ment, but remain as tensions, much like those which we find 

 in unannealed glass, giving the mass a tendency to fly into 

 pieces. Moreover, glacier ice is peculiar in that it is always 

 penetrated by numerous rifts or imperfectly closed fissures, 

 which accelerate its breaking whenever it is violently dis- 

 turbed. Owing to tlie more or less irregular melting which 

 goes on upon the outside of a berg, its centre of gravity grad- 

 ual!)' clianges, so that from time to time it rolls over in the 

 sea. Such accidents are not infrequently observed by Arctic 

 explorers and whalers who haunt the waters where these ice- 

 fields most abound. As may be imagined, when one of these 

 vast masses somersaults, every part of it is subjected to vio- 

 lent stresses which would rack much more solid structures, and 

 also that, when they strand in some shallower part of the sea 

 a like trial of their strength occurs. In fact, when either of 

 these accidents happens, the berg often flies into pieces almost 

 as does a Prince Rupert drop of quickly cooled glass when it 



