58 THE GLACIAL LAKE AGASSIZ. 



basin. In crossing the Red Rivei- Valley the Pembina runs in a channel 

 only 20 to 40 feet deep. Its descent from the northern base of Turtle 

 Mountain to Walhalla is about 700 feet, and thence to its mouth 186 feet, 

 its junction with the Red River being 748 feet above the sea. Long or 

 White Mud River, Clear Water or Cypress River, and Tongue River are its 

 chief tributaries, all from the south side. 



Assinihoine River. — The largest tribvitary of the Red River is the 

 Assiniboine, which di'ains a basin in Assiniboia, Manitoba, and North 

 Dakota, 300 miles wide from south to north and 400 miles long from west 

 to east. From its source in the south edge of Saskatchewan, 50 miles 

 southwest of the Porcupine Hills, the Assiniboine flows south-southeasterly 

 200 miles, to a point about 50 miles below the mouth of the Qu'Appelle 

 and 40 miles west of Brandon; thence it flows easterly about 150 miles to 

 its mouth. Its height above sea-level at the mouth of the Qu'Appelle 

 is 1,264 feet; at the bridge of the Canadian Pacific Railway near Brandon, 

 1,161 feet; at the mouth of the Souris, about 1,075 feet; at Portage la 

 Prairie, 842 feet, and at its junction with the Red River in Winnipeg, 724 

 feet. During its high stages of water the Assiniboine has been navigated 

 by steamboats to Fort Pelly, about 90 miles above the mouth of the 

 Qu'Appelle. Along this portion it varies from 10 to 25 rods in width. 



The highest floods of the Assiniboine at Portage la Prairie .and along 

 a considerable distance eastward rise only 12 to 15 feet above its lowest 

 stage, but they then attain a height only a few feet below the highest 

 portions of the adjoining country, much of which is submerged. At this 

 extreme height, which the river reached and maintained from the 3d to the 

 15th of May, 1882, the only time of such high water since 1860 or 1861, 

 it ovei-flowed near the former site of the fort of the Hudson's Bay Company, 

 2 miles southwest of Portage la Prairie, and a portion of its flood passed 

 north in shallow, winding watercourses to Lake Manitoba, making a 

 descent of about 40 feet in the distance of 15 miles between the river and 

 the lake. Near the same time Lake Manitoba also reached its highest 

 stage, about 8 feet above its lowest level, rising until it ovei'flowed south- 

 ward across the east part of township. 13, range 6, and thence eastward 

 through the southern row of sections in township 13, range 5, fiiUing 



