320 THE VOYAGE OF THE VEGA. [chap. 



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 

 liappens 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 ^.nally leads to its bursting into 

 a thousand pieces. We have here a Prince Rupert's drop, but 

 one w^hose 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-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 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 

 have there been exposed to a comparatively early summer heat. 

 The bay ice therefore melts away completely during summer, 

 and it is not commonly much pressed together. When all the 

 snow upon it has disappeared, there is to be seen above the 

 surface of the water a little ice of the same colour as the water, 

 while under water very considerable portions of unmelted hard 

 ice are still remaining. This has given rise to the walrus- 

 hunters' statement, which has been warmly maintained, that the 

 ice in autumn finally disappears by sinking. Nearly all the ice 

 we met with in the course of our vo3'age belonged to this 

 variety. 



6. iSea Ice, or heavy ice, which often exhibits traces of having 



