Chap. X. 



CLEAVAGE OF ICE. 



209 



edges with zigzag fracture, almost as in diamond cleavage of 

 slate ; this condition may have been produced by peculiar 

 exertion of pressure in this particular berg. 



When the lower cliff of the two storied berg, described and 

 figured in the text, had a shot fired into it, large masses of ice 

 fell, raising a considerable swell in the sea. The pieces of 

 the cliff split off in flat masses parallel with the face of the 

 cliff, just as I noticed to be the case in the splitting of the 

 glacier cliffs at Heard Island, and did not tumble forward but 

 slid down the face of the cliff, keeping their upper edges, parts 

 of the old plateau surface, horizontal. 



The ice floated round the ship in some quantity ; it was 

 opaque and white-looking, somewhat like white porcelain, and 

 the shattered fragments had remarkably sharp angular edges, 

 showing that the ice was very hard and compact, far more so 

 than its appearance in mass would 

 lead one to suppose, since it looks 

 at a distance as if it were hardly con- 

 solidated, but merely closely pressed 

 snow. Its manner of cleavage only 

 gives evidence at a distance of its 

 very compact nature. 



Many of the floating fragments were 

 traversed by parallel veins of trans- 

 parent ice, which were those which, 

 when seen on a cliff surface, look 



blue. A shot fired at the top of the higher cliff produced 

 no effect, the ball apparently going in without splitting off any 

 ice at all. 



The greater approximation of the strata towards the base of 

 the bergs is no doubt due to the increasingly greater pressure 

 sustained by them. The blue lines seem to represent successive 

 slight surface thawings of superimposed falls of snow. In 

 these lines of clear transparent ice, a complete fusion of the 

 snow particles has taken place. The opaque white ice between 

 them though, as appears from its fracture, very compact, is 

 less so than these bands, as shown by its being melted 

 sooner.* 



There can hardly be a doubt that the ice must be of increas- 

 ing density from its summit downwards. 



Several small bergs were passed, which showed hardly any 

 blue stratification in their cliffs ; the top surfaces of these 

 showed rounded conical hillocks, and a general appearance 

 of formation by wind drifting of the snow. What few bands 

 were present, were conformable in curve with the irregular 



* See preceding page. 



14 



FRACTURE OF ICE CLIFF. 



