Relation of Ldfaijette Uplift to Qlacintion. — Uphaxi. 341 
western Europe. The ice surface over Sweden, and over the 
Laurentide highlands of Canada and the basins of lakes Su- 
perior and Winnipeg, was probably one to two miles higher 
than the land, equaling or exceeding the Greenland ice-sheet, 
which rises in its central part 8,000 to 10,000 feet above 
the sea. 
Nature and Source of Epeihogenic Movements. 
LeConte, in his recent presidential address before the Geo- 
logical Society of- America, expresses tiie opinion that "no 
adequate cause has been assigned snid no tenable theory pro- 
posed" to account for the widespread epeirogenic movements 
which have occurred through all the earth's histor3^ but per- 
haps never on a grander scale than dui ing the latest and pres- 
ent, comparatively short. Quaternary era. It seems to me, 
however, that these great but slow and long continued crustal 
movements are a part of the results of the earth's contraction 
by the gradual and constant cooling of its interior. The crust, 
being hard and rigid, must adapt itself by deformation to the 
very slowly diminishing mass of the plastic or molten interior. 
This is effected, as I believe, between the times of great fold- 
ing and upheaval of mountain chains, by the moderate distor- 
tion of the earth's general form, uplifting parts f>f the conti- 
nental areas and depressing other lands or mostly parts of the 
ocean basins, until the accumulating gravitative stress of the 
deformed crust, when thus broadly uplifted and elsewhere 
depressed, shall be sufficient to crumple some belt into a moun- 
tain range. Then the elevated or protuberant areas sink to an 
isostatic condition, with the formation of faults and tilting of 
large crustal blocks, producing extensive monoclinal moun- 
tains, such as are exemplified by the latest movements of the 
Sierra Nevada and Wasatch mountain belts, and even by the 
origin of many minor mountain ranges of the Great Basin of 
the western United States. 
This view I first stated in 1889,* and have since given it 
prominence in numerous papers touching on tiie causes of the 
Ice age. Like LeConte, in his address before quoted, I think 
that "elevation was, at least, one cause, probably the main 
=*= Wright's Ice Age in North America, ayjpendix, pp. 573-595. Compare 
Appalachia, vol. vi, 1891, pp. 191-207 (also in the Popular Science 
Monthly for Sept., 1891). 
