LANGS VALLEY AND THE PEMBINA EIYER. 57 



a channel 20 to 30 feet lielow the flat lacustrine plain. This lower portion 

 of the river is mostly from 50 to 75 feet wide and 1 to 3 feet deep. The 

 Maple River, flowing south and then noitheast, parallel with the She}'enne, 

 joins this river about 8 miles from its mouth. The large valley of the 

 upper part of the Sheyenne River, and its extensive delta deposited in 

 Lake Agassiz, are attributable to a stream which was doubtless much larger 

 than the present Sheyenne, formed by di-ainage from tlie ice-sheet when it 

 terminated near Devils Lake. At that time, also, a glacial lake in the basin 

 of the Souris outflowed s(iutheastward to the Sheyenne and James rivei-s. 



Langs Vallei/. — During a later stage in the recession of the ice-sheet 

 the glacial Lake Souris was extended west and north of Turtle Mountain 

 and finally found a lower outlet in southern Manitoba. Its outflowing i-iver 

 ran southeasterly from the elbow of the Souris, 18 miles southwest of its 

 mouth, to the Pembina River. Pelican Lake, 11 miles long from northwest 

 to southeast and about a mile wide, occupies a part of the channel of this 

 stream; and a distinct water course of similar width, called Langs Valley,^ 

 eroded 110 to 150 feet below the general level, extends 11 miles between 

 this lake and the Souris. The highest poi-tion of Langs Valley is 1,364 

 feet above the sea, and about 100 feet above the Souris at its elbow, and is 

 inclosed by bluff's 110 feet high. It is a channel similar to that of Lakes 

 Traverse and Big Stone and Browns Valley, eroded by the River Warren, 

 outflowing- fi-om Lake Agassiz. 



Pemhhui River. — The Pembina River^ flows from tlie northern part of 

 Turtle Mountain in a rather crooked easterly course through southern 

 Manitoba and the edge of North Dakota about 130 miles, measured in a 

 direct line, to its mouth at Pembina and St. Vincent. From its junction 

 with the outlet of Pelican Lake to Walhalla, at the base of the First 

 Pembina Mountain, its valley varies from 175 to 450 feet in depth. Rock 

 Lake and Swan Lake, on this part of the river, each several miles long and 

 from a half mile to 1 mile wide, are due to deposits brought into this valley 

 by tributaries after it ceased to be the avenue of drainage from the Souris 



'Named for James Laiii;, wbo was the first iinmigraut here, coming iu 1880. 



•This name is stated by Keating to be from the Ojibway word "auepeminau, which name has 

 been shortened and corrupted into Pembina," meaning the fruit of the bush cranberry ( nburnum 

 opulm, L.). — Narrative of Long's Expedition. Vol. II, p. 38. 



