424 
THE VOYAGE OF THE VEGA. 
[chap. 
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 Spitz- 
bergen 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-fcot 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 rotten that they soon 
melt away and disappear. 
5. The walrus-hunters’ Bay Ice ; by which we understand level 
ice-fields formed in fjords and bays along the coast, and which 
