




B. N. A. BOUNDARY COMMISSION. 


formed by the rocky front of the Laurentian; but east of the Red R ri 
it is bounded by the high-lying drift terraces surrounding the Tale ne)0F «. 
the Woods, and forming a part of the drift plateau of northern Minnes esota. 
To the west, it is limited by the more or less abrupt edge of the sec 
prairie level, forming an escarpment, which, though very regular insome _ 
places, has been broken through by the broad valleys of the Assineboir eo ‘ 
and other rivers. The escarpment, where it crosses the Line, is knoy i a 
as Pembina Mountain, and is continued northward by the Riding, Deon Bi at 
Porcupine, and Basquia Hills. The average height above the sea, of this x a a 
lowest level of the interior continental region is about 800 feet ; the lowest | 
part being that surrounding the Winnipeg group of lakes, which have : 
an elevation of about 700 feet. From this it slopes up southward, and — a 
attains its greatest elevation—960 feet—at its termination far south in ish 3 
Minnesota. The edges of this prairie level are also, notwithstanding its — a 
~ apparent horizontality, considerably more elevated than its central line oa. 
: which is followed by the Red River. Its width on the forty-ninth parallel 
is only fifty-two miles; its area, north of that line, may be estimated at 
| 55,600 square miles, of which the great system of lakes in its northern 
cw part—including Lakes Winnipeg, Manitoba, Winnipegosis, Cedar and St. 
ae’ Martin’s—occupies 13,900 miles. A great part of this prairie level is 
A. wooded more or less densely, and much of the low-lying land near the 
" great lakes appears to be swampy and liable to flood. The southern 
part, extending from the boundary line nearly to the south end of Lake 
< , Winnipeg, includes the prairie of the Red River Valley, with an area of — 
about 6,900 square miles; one of the most fertile regions, and, at the 
same time, the most accessible portion of the North-west. 
7. The superficial deposits of this stage are chiefly those of a great 
lake which occupied its area after the glacial submergence. This partof 
the interior of the continent being the last to emerge from the Arctic 
? waters, and having been covered for a long time afterward by aseaof 
, fresh water, held back either by drift deposits, or by rocky barriers, which — 
have subsequently been cut through, and which must have united all the 
y lakes now found in the region into one sheet of water, which extended : 
with narrower dimensions about two hundred miles south of the Boundary 































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; line. . 
‘ The Red and Assineboine Rivers and their tributaries have not yet % 
cut very deeply into its alluvial deposits, and its surface is level and little — 4 : 
furrowed by denudation. ae 
8. The second steppe of the plains, is bounded to the east as already — 
é 
+ 
