ASSINIBOINE, QU'APPELLE AND SOUEIS RIVERS. 59 



10 feet in 15 miles to Long Lake, through which old channel of the 

 Assiniboine its waters were discharged into/ this river 20 miles east of 

 Portage la Prairie.^ 



The excavation of the Assiniboine basin, before mentioned in con- 

 nection with the description of Pembina, Riding, and Duck mountains, 

 depressing much of its area hundreds of feet below the great plains 

 farther south, was effected by preglacial rivers. Over the irregular surface 

 thus sculptured a thick covering of glacial di-ift is spread somewhat uni- 

 formly, so that the preglacial contour is preserved in the broader outlines 

 of the country; but the smaller inequalities of the surface and the present 

 watercourses have been formed during Glacial and Recent time. 



While Lake Agassiz held nearly its highest level, the Assiniboine 

 brought into its west side a vast delta, of gravel and sand, which extends 

 from Brando'n 75 miles east to Portage la Prairie, and from Treherne, 

 Glenboro, and Milford 40 miles north to Gladstone and Neepawa. Its area 

 is fully 2,000 square miles, and its depth probably averages 50 feet, with a 

 maximum of about 200 feet. 



Qu^Appelle and Souris rivers. — The QuAppelle or Calling- River and 

 the Souris or Mouse River are the largest tributaries of the Assiniboine. 

 Each of these streams has an interesting glacial history, which is recorded 

 in the topographic features of their valleys and areas of di'ainage. The 

 Qu'Appelle Valley was eroded by the outlet of a glacial, lake in the basin 

 of the South Saskatchewan River. The description, map, and sections 

 given by Hind^ show that this valley is quite uniformly about 1 mile wide, 

 and is eroded from 110 to 350 feet below the general level of tlie region 

 through which it lies, this height being reached by steep blufts on each 

 side. Its length from the elbow of the South Saskatchewan to its junction 

 with the Assiniboine is about 270 miles, the general coiu'se being a little 

 to the south of east. Of this extent the west end of the valley for about 

 12 miles is occupied by the River that Turns, and the remainder by the 

 Qu'Appelle, the summit or height of land in this channel at the divide 



'Compare H. S. Treherne's description of this vicinity, "An ancient outlet of Lake Manitoba," 

 Ninth Annual Report of the Geol. and Jsat. Hist. Survey of Minnesota, for 1880, pp. 388-392. 



- Report ot the Assiniboine and Saskatchewan Exploring Expedition, 1859, by Henry Youle Hind. 



