294 ASSINNIBOINE AND SASKATCHEWAN EXPEDITION. 



their sides an opuntia is very common. The prairie on the 

 west of the Souris as well as on the east is treeless, but the 

 banks of Plum Creek support a thin belt of small forest 

 trees, such as oak and ash, with a few ash-leaved maple. 



The annual fires prevent the willows 

 and aspens from covering the country, 

 which they would undoubtedly do until 

 replaced by other species, if not de- 

 stroyed to within a few inches of the 

 root every time the fire sweeps over 

 them. The banks of the Souris here are 

 not more than 40 feet high, with level 

 prairies on either hand, a few miles 

 beyond the Snake Hills. Within four 

 miles of the mouth of Plum Creek, 

 Oak Lake, several miles in diameter, 

 attracted the hunting portion of our 

 party ; they brought back some peli- 

 cans and a score of duck. Thunder 

 storms as usual to day and yesterday. 



On the 1st July we arrived at the 

 Souris Sand Hills, and made a section 

 of the river bank where a land slip 

 had produced a fine exposure to the 

 water's edge. The formation con- 

 sisted of five feet of blue clay above 

 the level of the river, supporting four 

 feet of ferruginous sand and gravel, 

 on which reposed twelve feet of sandy 

 loam and sand to the prairie level. 

 The blue clay, capped by the ferru- 

 Section on theLittk Souris, g mous sant [ ? wag traced for a distance 



►showing ancient Beaches 0 



(6, c, d, /, g) oi I \ miles, and snowed a dip to the 

 with Lignite Boulders. SO uth of two feet in the mile, the 



