of Spitzbergen.

Glacier-ice shows a great disposition to fall asunder into smaller
pieces without any perceptible cause. It is full of cavities,
containing compressed air, which, when the ice melts, bursts its
attenuated envelope with a crackling sound like that of the electric
spark. It thus behaves in this respect in the same way as some
mineral salts which dissolve in water with slight explosions.
Barents relates that on the 20/10th August 1596 he anchored his
vessel to a block of ice which was aground on the coast of Novaya
Zemlya. Suddenly, and without any perceptible cause, the rock of ice
burst asunder into hundreds of smaller pieces with a tremendous
noise, and to the great terror of all the men on board. Similar
occurrences on a smaller scale I have myself witnessed. The cause to
which they are due appears to me to be the following. The ice-block
while part of the glacier is exposed to very severe pressure, which
ceases when it falls into the sea. The pressure now in most cases
equalises itself without any bursting asunder, but it sometimes
happens that the inner strongly compressed portions of the ice-block
cannot, although the pressure has ceased, expand freely in
consequence of the continuous ice-envelope by which they are still
surrounded. A powerful internal tension must thereby arise in the
whole mass, which finally leads to its bursting into a thousand
pieces. We have here a Prince Rupert's drop, but one whose diameter
may rise to fifty metres, and which consists not of glass but of
ice.

Glacier ice-blocks occur abundantly on the coasts of Spitzbergen and
north Novaya Zemlya, but appear to be wanting or exceedingly rare
along the whole north coast of Asia, between Yugor Schar and Wrangel
Land. East of this they again occur, but not in any great numbers.
This appears to show that the Western Siberian Polar Sea is not
surrounded by any glacial lands. The glacier ice is commonly of a
blue colour. When melted it yields a pure water, free of salt.
Sometimes however it gives traces of salt, which are derived from
the spray which the storms have carried high up on the surface of
the glacier.

3. Pieces of ice from the ice-foot formed along the sea beach or the
banks of rivers. They rise sometimes five or six metres above the
surface of the water. They consist commonly of dirty ice, mixed with
earth.

4. _River Ice_, level, comparatively small ice fields, which, when
they reach the sea, are already so r