In short, the glaciers of the Alps-and the statement holds good, as will be seen presently, of other mountain regions are but the dwindled representatives of gigantic predecessors, to which, at any rate on the Swiss lowland, we can hardly refuse the name of ice-sheets.

CHAPTER II

ARCTIC AND ANTARCTIC ICE-SHEETS

LAND-ICE has left its marks on the Alpine region, but in Greenland it is still in possession. The Glacial Epoch belongs to the past in the one, to the present in the other. Every process which has sculptured the surface and formed the glacial deposits of lands wherein a milder climate now prevails, should be found at work in Greenland and the adjacent parts of the Arctic region. Here the results which, in more southern countries, are subjects for conjecture, should be actual matters of fact. Of late years much has been learned about Greenland itself, not only from the members of sundry expeditions to circumpolar regions, but also from the special investigations of Steenstrup, Nordenskiold, Nansen, Peary, and others. From the accounts which have been published we shall endeavour to select those facts which seem likely to throw light on the behaviour and work of ice during a Glacial Epoch.

Greenland is the only very important land mass which, in the Northern Hemisphere, extends beyond the seventy-ninth parallel of latitude. Over almost

the whole region the mean annual temperature is below the freezing-point of water in the extreme north it is probably not higher than 4° F.-while the cold during the long winter months is intense, the January temperature about latitude 70° being often as low as 32°. It is not probable that the climate in any part of Europe during the Glacial Epoch was as severe as this, so that we may regard Greenland as exhibiting a picture of cold the effects of which cannot have been outdone in the past history of that continent.

A study of the Arctic regions quickly impresses one fact upon our minds, viz., the markedly unequal distribution of the larger masses of land-ice. This completely covers a very large part of Greenland, while there are few glaciers of importance in Grinnell Land on the opposite side of Smith Sound.1 The other islands north of the American continent, though some are of a fair size and rise to a considerable elevation, nowhere exhibit an accumulation of ice in any way comparable with that of Greenland. The same is true of the northern part of Siberia; the cold there is no less intense than in the north of the other continent; a very large slice of Siberia is

1 "A very noticeable feature of Grinnell Land is the paucity of glaciers and the non-existence of an ice-cap, such as prevails in North Greenland. In Grinnell Land, north of latitude 81°, no glaciers descend to the sea-level, which they do in the same parallel on the opposite or Greenland coast of Hall Basin." - Captain Feilden, Quart. Jour. Geol. Soc., xxxiv. p. 567.

included within the annual isotherm of 32° F., no inconsiderable piece within that of 5°, while the January temperature of Yakutsk, in latitude 62° north, is as low as 40° F., and the soil is permanently frozen to a depth of about 700 feet. Yet in all this region, notwithstanding the intense cold, glaciers are unknown. The reason is simple: the

air is dry and the snowfall is but light. So far as temperature goes, a Glacial Epoch rules in Siberia, but no marks of ice action will be left behind in the event of its departure.

Something more, however, is necessary for the formation of an ice-cap, namely, a large land area. A mantle of perpetual snow swathes the islands of the Arctic Ocean-not only those of smaller size on the Greenland coast, but also those, both small and large, to the north of the American continent; yet in none is an ice-sheet found; this seems to require a land mass of almost continental dimensions. The more boldly the district is sculptured, the more easily, cæteris paribus, glaciers seem to form. A fairly level island will be merely snowcapped; its shores in summer time may be uncovered and support a scanty vegetation; but in one that rises into mountains, glaciers will stream down the valleys and enter the sea. Still, even here, the amount of ice appears, as might be expected, to be proportionate to the area of the gathering-round. There are important glaciers in Spitzbergen and in Franz Joseph's Land, but these are hardly to be com