CHEMICAL AND -PHYSICAL NOTES. 89 
' Another educational preliminary for the members of a land ex- 
pedition is to acquire as much skill as possible in ski running and 
the method of travel adopted by Nansen in crossing Greenland. For 
this purpose a short visit to Norway in winter would be useful. The 
way into the Antarctic interior will almost certainly be over land ice, 
and if it is the ice which is the parent of the great tabular bergs 
so well known from illustrations, it is probable that travelling over 
it will not be very difficult in so far as the nature of its surface is con- 
cerned. It has long been known that the glaciers of Greenland travel 
much more rapidly than those of Switzerland, but it is only since 
the publication of v. Drygalski’s remarkable observations,* carried on 
throughout the year on the glaciers of the west coast of Greenland, 
that we know that in some cases the motion of the ice reaches the 
astonishing rate of 18 metres in twenty-four hours, and that this rate 
of motion is very little affected by the change of season. According 
to Drygalski, what chiefly affects the motion of a glacier is its mass. 
Great as are the glaciers of Greenland, there can be little doubt that 
the parents of the Antarctic tabular icebergs are many times greater. 
If conditions such as these exist on the Antarctic land, it is little 
wonder that the supply of tabular icebergs is so abundant. Dr. 
Argtowski has described how, on the occasions when he landed on 
the rugged coasts visited by the Belgica, and the weather was calm, 
the thunder of falling ice was continuous. On Heard Island, during 
the short visit which the writer was able to pay it from the 
Challenger, the fall of ice from the western portion was also nearly 
continuous. 
Since the days of Hugi and Agassiz, the intimate structure of 
glacier ice has been the object of much study by Continental and 
chiefly Swiss naturalists. Englishmen, though they frequent glaciers 
as much as any other nation, have generally ignored it. Tyndall, to 
whom we owe so much of our knowledge about ice, recognised the 
existence of the grain of the glacier, as it is called, but made no use 
of it in his speculations with regard to the nature of the motion of 
glaciers. As his theories are independent of this fundamental feature 
of the constitution of glacier ice, they must be pro tanto incomplete. 
The colour of the surface of a glacier, so dazzling in its whiteness that: 
the inexperienced beholder is apt to suppose it covered with freshly 
fallen snow, is due to the disintegration of the compact blue glacier 
ice into its constituent grains under the influence of the radiation 
of the sun. There is no more instructive or more impressive experi- 
* *Gronland Expedition, 1891-1893, unter Leitung von Erich von Drygalaki.’ 
Berlin, 1897. 
