
GLACIAL PHENOMENA AND SUPERFICIAL DEPOSITS. 237 
over the low country of the Red River Valley. By such a series of 
suppositions, nearly all the observed phenomena may be accounted for; 
while it is easy to attribute the uniformity of the plains, to the action of 
such a glacial sheet planing its surface ; but an almost infinite amount of 
force, acting from behind, must be among the first of the assumptions; a 
force capable of moving the supposed great ice-mantle across the 
northern transverse watershed, down into the valley of the Saskatch- 
ewan, lying athwart its course, and then for hundreds of miles up the north- 
eastward slope of the plains. 
545. The main facts to be accounted for are these :—A plateau in 
continuation of the high land stretching eastward from the mountains ; 
thinly covered with drift material of the nature of shingle, in which 
quartzite fragments from the slopes of the Rocky Mountains greatly pre- 
ponderate, 
A lower region to the southward, also characterized by quartzite 
drift, in which, when most perfectly sheltered from the north, northern 
and eastern drift, rarely occurs; but appears to increase in abundance in 
exact proportion to the deficiency of the northern barrier. 
A second lower region to the north, thickly covered with glaciated 
northern arid eastern debris, with comparatively little intermixture of 
western material, and heaped up especially on the foot of the plateau 
before mentioned. 
546. From a careful examination of the Coteau and its surroundings 
in the vicinity of the Boundary-line, I have been lead to the opinion that 
not glacier-ice as such, but sea borne icebergs only, can account for the 
phenomena there presented. From the great similarity of the natureof 
the Coteau in all parts of its length, and its essential unity, it would seem 
that the nature of the origin of any one part must be that of the whole. 
Without therefore at the present time entering at any length into the 
general question of glaciation, it may be well to attempt to account as 
far as possible for this its greatest record on the plains. 
547. It will be shown subsequently, that a depression of the continent 
amounting to at least 4,000 feet, as marked in the Rocky Mountain region, 
has taken place in post-tertiary times, and during the subsidence and 
emergence preceding and following the period of greatest depression, it 
would seem that most of the features of the later deposits of the plains 
were produced. To account for the Coteau deposit, it must be supposed 
that from some cause the level of greatest deposition of drift material, for 
some time coincided with its general altitude ; but whether this line was 
