FORMS OF ICEBERGS 35 



Figs. 12, A F, illustrate a few forms additional to 

 those shown in the photographs. Fig. A shows a 

 large berg probably about 1 50 ft. above the water, 

 weathered into its present shape from a tabular 

 block detached from a glacier: Fig. A was drawn 

 on August 29; by August 30 the collapse of the 

 arch (Fig. B) had converted the berg into two, 

 apparently separate bergs connected below the 

 water-level. A similar alteration of form due to the 

 rupture of a large central aperture is illustrated by 

 Figs. E and F. The black patch in the lower part 

 of the white cliff of the massive tabular berg seen 

 in Fig. C represents an area of brilliant cobalt 

 blue, which probably means that formerly, when 

 the ice was still included in a glacier, there was a 

 channel occupied by a stream: the water subse- 

 quently froze into a brilliant blue mass. A not 

 uncommon type of surface sculpture is shown in 

 Fig. D: unequal melting produced a series of 

 parallel grooves and ridges. 



The life-history of a large iceberg towering 100 

 ft. or more above the sea and with a much greater 

 mass varying according to the density of the ice 

 below the water, would make an interesting 

 story. When calved from the face of a glacier an 

 iceberg may be launched as a flat tabular block 

 a few hundred feet in length; for a time it retains 

 its original form, but as it drifts to sea and is 

 exposed to the wash of the waves and encounters 

 different temperatures, air at high tension, im- 

 prisoned in cavities in the ice, has the pressure 

 reduced and this acts like an internal explosion, 



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