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 150 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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