Ice Age in Xorfh Americd and Europe. — rphani. 103 
the Thames, and the simihtr traces of man in high terraces of 
the Somme valley, attest his existence there before the maxi- 
mum stages of the uplift and of the Ice age. America ap- 
pears also to have been already peopled at the same early time. 
The accumulation of the ice-sheets, due to snowfall upon 
their entire a"reas, was attended by fluctuations of their grad- 
ually extending boundaries, giving the Scanian and Norfolk- 
ian stages in Europe, and an early glacial recession and re- 
advance in the region of the Moose and Albany rivers, south- 
west of Hudson bay. 
2. Kansan stage. Farthest extent of the ice-sheet in the 
Missouri and Mississippi river basins, and in northern New 
Jersey. The Saxonian stage of maximum glaciation in Eu- 
rope. 
Area of the North American ice-sheet, with its development 
on the Arctic archipelago, about 4,000,000 square miles ; of 
the Greenland ice-sheet, then somewhat more extended than 
now, 700,000 square miles or more, probably connected over 
Grinnell land and Ellesmere land with the continental ice- 
sheet [the area of Greenland is approqimately 680,000 square 
miles, and of its present ice-sheet, 575,000 square miles] ; of 
the European ice-sheet, with its tracts now occupied by the 
White, Baltic, North, and Irish seas, about !2, 000,000 square 
miles. 
Thickness of the ice in northern New England and in cen- 
tral British Columbia, about one mile ; on the Laurentide high- 
lands, probably two miles ; in Greenland, as now, probably one 
mile or more, with its surface 8,000 to 10,000 feet above the 
sea; in portions of Scotland and Sweden, and over the basin 
of the Baltic sea, a half mile to one mile. 
3. Helvetian ok Aftonian stage. liecession of the ice- 
sheet from its Kansan boundary northward about 500 miles to 
Barnesville, Minn., in the Red river valle}' ; 250 miles or more 
in Illinois, according to Leverett ; but probably little between 
the Scioto river, in Ohio, and the Atlantic coast, the maximum 
retreat of that portion being 25 miles or more in New Jersey, 
A cool temperate climate and coniferous forests up to the re- 
ceding ice border in the upper Mississippi region. Much eros- 
ion of the early drift. 
The greater part of tli ' drift area in Russia i)ernianently I'e- 
