192 W. TJPIIAM — PLEISTOCENE AND PRESENT ICE-SHEETS. 



of Norway, have also contributed much to our knowledge of the ice-sheets 

 of the Pleistocene or glacial period. The vast ice-sheets of that time, 

 however, are adequately exemplified at the present day only by the 

 Antarctic and Greenland ice-sheets, less completely and on a much 

 smaller scale by the yet very instructive Malaspina glacier, and in some 

 respects they may be profitably compared with the Muir glacier, which 

 is the most fully studied ice-field of America or perhaps of the world. 



The Antarctic Ice-sheet. — Land ice surrounds the south pole to a distance 

 of 12 to 25 degrees from it, covering, according to Sir Wyville Thomson, 

 about 4,500,000 square miles. Its area is thus slightly greater than that 

 of the Pleistocene ice-sheet of North America, which covered about 

 4,000,000 square miles, while the confluent Scandinavian and British 

 ice-sheets appear to have enveloped no more than 2,000,000 square miles, 

 including the White, Baltic, North and Irish seas, whose areas were then 

 occupied by the continental mer de glace. Whether the Antarctic ice- 

 sheet covered an equal or greater extent in the Pleistocene period, con- 

 temporaneous with the glaciation of now temperate regions, we have no 

 means of knowing. Along a portion of its border of perpendicular ice- 

 cliffs Sir J. C. Ross sailed 450 miles, finding only one point low enough 

 to allow the upper surface of the ice to be viewed from the masthead. 

 There it was a smooth plain of snowy whiteness, extending as far as the 

 eye could see. That this ice-plain has a considerable slope from its cen- 

 tral portions toward its boundary is shown by its abundant outflow into 

 the sea, by which its advancing edge is uplifted and broken into multi- 

 tudes of bergs, many of them tabular, having broad, nearly flat, tops. 

 As described by Moseley in " Notes by a Naturalist on the Challenger" 

 these bergs give strange beauty, sublimity and peril to the Antarctic 

 ocean, upon which they float away northward until they are melted. 

 Many parts of the borders of the land underlying this ice-sheet are low 

 and almost level, as is known by the flat-topped and horizontally strati- 

 fied bergs, but some other areas are high and mountainous. Due south 

 of New Zealand the volcanoes Terror and Erebus, between 800 and 900 

 miles from the pole, rising respectively about 11,000 and 12,000 feet above 

 the sea, suggest that portions or the whole of this circumpolar continent 

 may have been recently raised from the ocean to form a land surface, 

 which on account of its geographic position has become ice-clad. 



The Greenland Ice-sheet. — Inside its border of mountains Greenland is 

 enveloped by an ice-sheet which lias a length of about 1,500 miles, from 

 latitude 60° 40' to latitude 82°, with a probable average width of 400 

 miles or more, giving it an area of 600,000 square miles. On the easf 

 this ice-sheet in some places stretches across the mountains, and the coast- 

 consists of its ice-cliffs; and on the west glaciers flow from the inland ice 



