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SMITHS* INIAN MISCELLANEOUS COLLECTK INS 



[vol. 47 



and very sparingly upon one or two other glaciers, may be termed 

 ice dykes. These consist of narrow crevasses, two to fifteen inches 

 across, completely filled with columnar ice, the columns being ar- 

 ranged horizontally, in a double series, at right angles to the walls 

 of the crevasse. In general the inner ends of the columns of each 

 series interlock at the center and the crevasse is completely filled. 



' "'*: 



Fig. 75. — Ice dyke, Lefroy glacier. 



In a few cases the columns do not meet and a narrow space is left, 

 exceptionally the columns are more or less uniformly curved. These 

 dykes are formed, in all probability, by crevasses becoming filled 

 with water and then freezing from the walls inward, the columns 

 forming at right angles to the freezing surface. The ice structure 

 conies out imperfectly in a photograph (fig. 75). In some few cases 

 ice dykes were noted which contained granular, instead of columnar 

 ice, which must have had an entirely different history. 



1 1. I J cat Reflection? — Still another phenomenon not known to have 

 been previously reported was observed as the snow was leaving that 

 portion of the glacier usuall) bare in the summer. It consists of a 

 large melted area upon the northern side of the boulders protruding 



