792 WALLACE W. ATWOOD 
west the narrowing is symmetrical, and the terminus of the range is 
lobate in form, being sharply defined at the north and south by the 
valleys of the Weber and Provo rivers respectively. To the east the 
narrowing is not so pronounced or symmetrical, and, associated with 
the general flattening-out of the range in that direction, helps to 
account for the less conspicuous terminus at the east. 
All the great canyons of the Uintas head near the crest of the range 
and descend approximately north or south. Since the axis of the 
range is nearer the north than the south margin, the north slope 
canyons are shorter than those on the south slope. All of the larger 
canyons have the characteristic U-shaped form due to glaciation. 
They have been well cleaned out by the ice in their upper portions, 
but in the middle and lower portions they contain heavy morainic 
deposits. 
On the north slope, at the heads of the canyons, the basins vary 
from one to twelve square miles in area, while on the south slope they 
commonly include from twenty to thirty square miles (see Fig. 1). 
This difference, which had a very notable influence on the size of 
the glaciers, is consistent with the general structure of the range and 
will be discussed later. 
THE EXTENT OF GLACIATION 
At the period of maximum extension the ice covered by far the 
greater portion of the mountains west of Longitude 109 degrees, 40 
minutes, and in a few cases extended beyond the mountains into the 
lower country to the north and south. The maximum extension of 
glaciation in an east-west direction was 82 miles, and in a north- 
south direction 42 miles. ‘The total area covered by ice was some- 
thing over 1,000 square miles. The portions of the range that rose 
above the ice near the crest-line were lofty peaks and narrow, rugged 
divides (see Figs. 2 and 3). Near the western end of the range in 
the region about Hayden Peak, Bald Mountain, Reids Peak, and 
Mount Watson, there was a great ice cap (see Fig. 1). Above this 
ice cap a few lofty summits (Fig. 2) rose as nunataks and helped to 
direct the movement of the ice into the canyons leading from this 
great center of accumulation. Six of the larger glaciers in the western 
portion of the range originated in this ice cap. 
