BOULDER PAVEMENT. 



389 



changing fast, and is becoming more undulating, patches of 

 aspens showing themselves on the prairie ; here and there, 

 however, the remains of a heavier growth are visible in 

 clusters of blackened trunks ten to fourteen inches in 

 diameter. "During the afternoon we anchored to measure 

 the rate of the current. The river is 200 yards broad, 

 and it flows three miles and a half an hour ; its average 

 depth is seven and a half feet. 



Some remarkable exposures of drift, consisting of clay, 

 enclosing horizontal tiers of boulders, (c,/,) often occur 

 after entering the wooded parts of the South Branch of the 

 Saskatchewan. The drift is exposed in cliffs at the bends 



Horizontal tiers of Boulders in drift on the South Branch, with polished Boulder 

 Pavement at the edge of the River. 



of the river, from fifty or eighty feet in altitude. The 

 fragments of shale, slabs of limestone, and small boulders 

 imbedded in the clay (d) are not arranged according to 

 the position they would assume if dropped by floating ice ; 

 some of them stand in the drift with their longest axis 

 vertical, others slanting, and some are placed as it were 

 upon their edges. They have the same forced arrangement 

 and position as the shale, &c, in the blue clay at Toronto. 



c c 3 



