224 B. N. A. BOUNDARY COMMISSION. 

characterized by swamps and lakes. Large areas of comparatively level, 
or only gently undulated ground, are however found in some places. The 
surface of the “ mountain” appears to be that of the drift, as deposited, 
and has been but little modified by subsequent sub-aerial action. The lakes 
ie in basin-like hollows, and notwithstanding their great number, drain- 
age vallies and stream-courses are few and unimportant. A considerable 
quantity of finer material, however, seems to have been removed from 
the hills and ridges, and re-deposited in the hollows, causing the former 
to be stony and gravelly. 
513. In many respects the structure of Turtle Mountain closely 
resembles that of the Coteau, elsewhere described, and from its altitude it 
is entitled to rank as an outlyer of the third steppe. Similar hills, more 
or less well marked, and composed of drift. materials, appear also to 
occur in other parts of the second prairie steppe. These, with Turtle - 
Mountain, form a line east of the escarpment of the third steppe, but 
nearly parallel with it, including from south to north :—Turtle Mountain, 
Moose Mountain, Wolf Hills, File Hills, Little Touchwood Hills, and Touch- 
wood Hills. These elevations do not appear to be connected with anything 
like a continuous escarpment, at least there is no such connection north- 
west of Turtle Mountain ; nor can their arrangement be shown to be due to 
any feature of the underlying rocks. They lie, however, nearly on a line of 
equal altitude on the eastward slope of the plains, and show a rough 
correspondence to the main gaps in the high land, connected with the 
escarpment of the second steppe, to the east.* Putting aside the 
hypothesis of a nucleus of limestone, or other solid rock, for which there 
appears to be no support, these elevations would seem to have been 
formed by the tendency of icebergs bearing debris to congregate in 
certain positions under the influence of currents. A shoal once produced 
in this, or any other way, would ténd to increase rapidly when the water 
became sufficiently shallow for the ice to ground on it, and its extent and 
dimensions would only be limited by the length of time during which 
suitable conditions prevailed, and the erosive power of the currents pass- 
ing over it, 
514. A careful examination of the pebbles of the drift, on the prairie 
east of the first crossing of the Line and Souris River, 170 miles west of 
Red River, gave the following ratios :— 
‘For a description of Moose Mountain. see Exploration of British North America, p. 49. For the 
Touchwood Hills, Report of Progress Geol. Surv, Canada, 1873-4, p. 28. 
