THE SHF>YENNE DELTA. 317 



JMucli ;illu\'iuin was also supplied from the erosion of the Sheyeuue 

 Valley, which, with that of the Big Coulee (the avenue of discharge from 

 the glacial Lake Souris to the Sheyenne and Lake Agassiz), probably 

 averages three-fourths of a mile in width and 150 feet in depth along a 

 distance of 200 miles. This channel is cut in the drift sheot, mainly till, 

 and in the underlying, easil}- eroded Cretaceous shales. The volume of the 

 material supplied from it would be equal, according to these estimates, 

 to about three-fourths of the Sheyenne delta, or perhaps three-eighths of 

 both the delta and the finer clayey sediments that were deposited farther 

 out in the lake. But the valley of the Sheyenne, in considerable portions 

 of its extent, was also a preglacial valley. If it retained in a considerable 

 degree its trough-like form beneath the ice-sheet, as was evidently true 

 of the Minnesota Valley,^ its erosion and its tribute to the Sheyenne delta 

 would be less than the proportion estimated. 



FROM SHELDON NORTH TO THE NORTHERN PACIFIC RAILROAD. 



(PLATES XXVII AND XXVIII.) 



The Herman beach, terrace-like, at Hugh Mcintosh's house, in the 

 south edge of the northwest quarter of section 8, Sheldon, has its crest 

 1,083 to 1,084 feet above the sea. His well, near the top of the beach, 22 

 feet deep, is soil and sandy clay to a depth of 7 feet, then sand 15 feet to 

 water. Till rises to the surface 20 rods farther west. About 30 rods east, 

 on laud 10 feet lower, a well 10 feet deep is all caving sand below the black 

 soil, which is 1 or 2 feet deep. 



Maple River in section 32, Highland, about 2 miles northeast from its 

 most southern bend, 1,019 feet. It is 20 to 40 feet wide and 1 to 3 feet 

 deep, with cobbles and bowlders in many portions of its channel. Herman 

 beach, a sand and gravel deposit, extending a quarter of a mile from south 

 to north on the verge of the bluff of till west of Maple River in tlie north- 

 west part of this section 22, 1,072 to 1,077 feet. In the north edge of the 

 northwest quarter of this section, the northeast corner of section 31, and 

 the east edge of section 30, it is a plateau-like tract a fourth of a mile wide, 

 with a subsoil of sand and fine gravel, 1,086 feet, from which both east and 



"'The Minnesota Valley in the Ice age," Proc, A. A. A. S., Vol. XXXII, for 1883, pp. 213-231. 

 Geology of Minnesota, Vol. I, 1884, pp. 479-485, 581 ; Vol. II, 1888, p. 134. 



