240 A NATURALIST ON THE "CHALLENGER." 



B.K, M.D., of the late Arctic Expedition, describes a similar 

 stratification as occurring in Arctic ice. He had opportunities 

 of examining the ice closely at leisure, and describes each 

 stratum as consisting of an upper white part merging into a lower 

 blue part, the colour depending on the greater or less number 

 and size of the air-cells in the ice.* 



Towards the lower part of the cliffs, the strata are seen to be 

 extremely fine and closely pressed, whilst they are thicker 

 with the blue lines wider apart, in proportion as they are traced 

 towards the summits of the cliffs. In the lower regions of the 

 cliffs, the strata are remarkably even and horizontal, whilst 

 towards the summit, where not subjected to pressure, slight 

 curvings are to be seen in them corresponding with the in- 

 equalities of the surface and drifting of the snow. 



In one berg there was in the strata at one spot, somewhat 

 the appearance of complex bedding, like that shown in iEolian 

 calcareous sand formations, such as those of Bermuda.! The 

 strata were often curved in places, but always in their main line 

 of run, horizontal, i.e., parallel to the original flat top of the berg. 

 The strata in the cliff at the level of the wash-line of a 

 rectangular berg 80 feet in height, were so thin and closely 

 packed, that they looked almost like the leaves of a huge book 

 at a distance, for by the lap of the waves the softer layers had 

 been to some extent dissolved out from between the harder. 

 In one berg where the face of the cliff was very flat and seen 

 quite closely with a powerful glass, the fine blue 

 bands were seen to be grouped, the groups being 

 separated by bands in which no lines were visible, 

 or where these were obscured by the ice frac- 

 turing with a rougher surface, not with a per- 

 fectly even and polished one, as existed where 

 ^r.^,.^ ^ , ,, the blue bands showed out. 



STRUCTURE OF ICE. 



a a Blue bands, bb The cliff surfaces, where freshlv fractured, show 



Layers without striae. 



an irregular jointing and cleavage of the entire 

 mass, very like that shown in a cliff of compact limestone. In 



* "Observations on Arctic Sea Water and Ice." Proc. Boy. Soc, 

 No. 189, 1878, p. 547. 

 t See p. 20. 



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