Icebergs iipon Drift 435 



innumerable fissures render the glaciers porous and permeable 

 to water. The dilatation of the water freezing in the crev- 

 ices, constantly tends to the enlargement of the glacier, which 

 must advance in the direction where there is the least resist- 

 ance, xllthoupjh, in some cases, the weight will add to its 

 progression, it is owing to this expansion, principally, that, at 

 certain seasons, the glaciers constantly tend to advance. It 

 would seem that fissures, precisely analogous to those of the 

 Alps and Spitzbergen, are seen on the glaciers or fixed ice- 

 bergs of the Antarctic regions. 



Captains Pendleton, Messrs. Ash and Davison, and Captain 

 Frederick G. Low, of Gloucester, all speak of the enormous 

 fissures or chasms which are found on the surface of the 

 glaciers, at the height of many hundred feet above the sea. 

 These fissures are described as running parallel with the 

 shore, and are often several miles in length. The observers 

 have particularly noted their length and width, from being 

 often obliged to walk along them for a great distance before 

 finding a place narrow enough to be crossed in safety. Cap- 

 tain Barnham judged that they were sometimes over five 

 hundred feet deeo, as he has been unable to see the bottom 

 when looking down. Captain Low informs me, by letter, 

 that he measured the depth of one eighteen inches wide, into 

 which he fell when the ice was covered with snow, although 

 he saved himself bv extendinsr his arms, and found it seventv- 

 five feet deep. The description given by all, of the extreme 

 beauty of the azure light reflected from the walls of the 

 fissures, strikingly reminds one of the accounts, given by 

 Agassiz and others, of the same appearance in the fissures of 

 the Swiss glaciers, a peculiarity of color which Agass'z says 

 is witnessed only in the mountain waters. 



Prof. Forbes says that these singular vaults on the Alps 

 have all the grotesque varieties of outline which are so much 

 admired in calcareous caverns, but which here show to far 

 greater advantage, in consequence of their exquisite transpa- 

 rency and lustre, and from being illuminated, instead of by a 



