Glaciatlon of Mountat7is, etc. — W. Uphain. 215 
winds was calmest wholly condensed and precipitated upon 
the southern part of the ice-sheet, so that it had a greater 
depth there than far north. The course of stria? and the 
directions in which the drift has been transported, together 
with the recorded observations of the upper limits of the drift 
on mountains, hills, and plateaus, indicate that a line of max- 
imum accumulation of ice extended from Newfoundland 
west-northwest to the southern part of Hudson bay, and 
thence west-southwest to the east base of the Rocky mountains 
between the Old Man and Waterton rivers, about twenty 
miles north of the north line of Montana. From this line or 
belt of its greatest depth the surface of the ice descended both 
to the south and north and the currents of its motion in these 
directions produced the glacial stria? and drift. 
In the culmination of each of the two principal glacial 
epochs, the thickness of the ice-sheet over central Newfound- 
land and Labrador was probably 3,000 to 6,000 feet, increasing 
to 10,000 or 12,000 feet on the Laurentian highlands and in 
the basin of James bay and over the south part of Hudson bay, 
the bottom of which is about 400 feet below sea level. Thence 
westward the ice-sheet in the earlier and more severe epoch 
of glaciation probably decreased in thickness to 8,000 or 
7,000 feet in the region of Reindeer and Winnipeg lakes, and 
farther west it declined to a depth of only 2,000 to 1,500 feet 
at the Cypress and Sweet Grass hills. Contemporaneous with 
this northeastern ice-sheet in its time of maximum extent, 
vast glaciers issuing from the Rocky mountains pushed against 
its western border, and another ice-sheet was formed on the 
Pacific side of the continent, covering nearly all of British 
Columbia. The greatest thickness of this western ice-sheet 
was apparently between latitudes 55° and 60°, and at a distance 
of two hundred to four hundred miles from the coast, attain- 
ing probabh' a depth of a mile or more above the land surface. 
Thence its motion was southward to the northern borders of 
Idaho and Washington, westward through the mountain 
ranges of the coast to the ocean, and northwestward, according 
to Dr. George M. Dawson in the Lewes and Pelly valleys of 
the upper Yukon basin. In the earlier glacial epoch, and })er- 
haps also the later, the northeastern and western ice-fields and 
the glaciers of the Rocky mountains became confluent, so that, 
when they covered their greatest area, one vast sheet of land 
