79 



It is however not without variety in its topography since 

 a large part of it is a northeasterly sloping plateau of 

 Mesozoic sediments etched into somewhat irregular surface 

 contour, and overlapping a lower plain having the irregular 

 features of the great pre-Cambrian shield. 



In the belt traversed by the railway lines, a threefold 

 division of prairie steppes rising one above the other to 

 the west is clearly recognizable, though the term prairie 

 may not be applicable farther north. These three divi- 

 sions are here adopted for descriptive purposes and a 

 fourth is added to include the broken, hilly country of the 

 foothills. 



The first and eastern division comprises the plain east 

 of the Cretaceous deposits which rise as a low escarpment 

 to form the plateau. The second extends from the edge 

 of this plateau westward to the erosion remnants of former 

 Tertiary deposits and the third from this line westward 

 to the foothills. 



First Division. — This division is the lowest in elevation 

 and is essentially a region of lakes, with the exception that 

 in the southern part the inequalities of the rock surface 

 have been smoothed over by the deposition of clays and 

 silts in glacial Lake Agassiz. This forms the rich farming 

 country of southeastern Manitoba, where the extreme 

 evenness of surface is noticeable because of the general 

 absence of timber. This plain is however being partly 

 forested by the individual efforts of the farmers. 



The surface features east and north of Lake Winnipeg 

 differ from those to the west in having the mammillated 

 character typical of a region underlain by Pre-Cambrian 

 rocks with but a thin mantle of drift. The large lake 

 basins are due mainly to the removal of Palaeozoic rocks 

 from the older westerly dipping rock surface. 



Traces of the margin of glacial Lake Agassiz remain 

 in distinctly marked beaches resting on the slopes which 

 rise upward to the Cretaceous plateau. 



The railway ascends to the Cretaceous plateau up 

 the wide delta and valley of the ancient Assiniboine river, 

 where it entered Lake Agassiz. The present drainage of 

 this region is northward to Hudson bay by Nelson river. 



Second Division. — This division is the lower or eastern 

 portion of the plateau and is underlain by a succession of 

 shale beds and other equally soft rocks. The surface is 

 about 1,000 feet (304 m.) above the Manitoba lakes or 



