340 THE GLACIAL LAKE AGASSIZ. 



Elk Valley, for 12 miles from Elm Grove and McCanna north to the 

 Forest River, is nearly constant in elevation, which is 1,155 feet on its 

 west border and 1,1 o5 feet near its east side, its average width being about 

 4 miles. 



Ujjper Herman beach, a definite and massive ridge of sand and fine 

 gravel, 25 to 40 rods wide, for a half mile south from the South Branch of 

 Forest River, in the west part of the northwest quarter of section 14, Elk- 

 mount, 1,173 to 1,178 feet, passing north and northwest, with a descent of 

 12 to 15 feet on the east and a depression of 4 to 8 feet on the west. 



Beyond this branch of the Forest River, in the north half of section 

 lO, Elkmount, the beach ridge, similar in outline, with its crest at 1,174 to 

 1,179 feet, is the site of an abandoned railway grade, on accoimt of which 

 its material is Avell exhibited. It is sand and gravel, and three-fourths of 

 the pebbles, mostly less than 2 inches in diameter, are dark-gray slat}' 

 shale. Twenty miles to the south-southeast the same shale in small grains 

 makes fully two-thirds of a stratum of sand that extends from 20 to 60 feet 

 in depth in the well at the Sherman House, Larimore. Pebbles of it were 

 also observed in kame-like deposits of gravel and sand near Balaton, Lyon 

 County, in southwestern Minnesota. During the further exploration of the 

 western shore of Lake Agassiz this shale was discovered in place, and is 

 found to be the bed-rock, of Cretaceous age, which forms the conspicuous 

 escarpment of the Pembina Mountain, though even there it is generally 

 covered and concealed by drift. 



Natural surface at the northwest corner of section 3, Elkmount, on the 

 line between Grand Forks and Walsh counties, 1,181 feet. The upper 

 HeiTQan shore passes north-northwesterly through this corner of section 3 

 and the east part of section 33, Medford, to the Middle Branch of Forest 

 River (farther east formerly called Salt River), which it reaches near the 

 center of the east half of section 28. It has only scanty deposits of beach 

 gravel and sand, nowhere forming a ridge; instead, the surface is mainly 

 till, very flat east of this shore, but undulating or rolling westward. 



The South and Middle branches of Forest River occupy valleys 25 to 

 40 feet deep and 20 to 30 rods wide. They are bordered with groves, or at 

 least a continuous line of trees, along the greater part of their course. 



