226 THE GLACIAL LAKE AGASSIZ. 



LATER OUTLETS NORTHEASTWARD. 



When the outlet of Lake Agassiz was changed and an avenue of dis- 

 charge toward the northeast was obtained, the south end of the lake at 

 first fell only 15 feet below the McCauleyville beach and the bed of Lake 

 Traverse. Its numerous stages, recorded by the .shore-lines of thie whole 

 time of northeastward outflow, until the retreat of the ice-sheet uncovered 

 the present course of the Nelson, were in succession each lower than the 

 preceding by the following- amounts, as determined mostly by leveling on 

 the latitude of Glad.stone, Manitoba, 308 miles north of Lake Traverse and 

 84 miles north of the international boundary: The first, second, and thu'd 

 Blanchard beaches, respectively, about 20, 15, and 15 feet; the Hillsboro 

 beach, 12 or 15 feet; the Emerado beach, about 30 feet; the Ojata beach, 

 25 feet; the Gladstone beach, 20 feet; the Burnside beach, again 20 feet; 

 the Ossowa beach, 15 feet; the Stonewall beach, 20 feet; and the Niverville 

 beach, 45 feet. Thence to the earliest level of Lake Winnipeg there was 

 again a fall of about 45 feet, and erosion by the Nelson River has since 

 lowered this lake about 20 feet. 



As soon as the ice upon Hudson and James bays and the adjoining- 

 country had so receded as to give to Lake Agassiz an outlet lower than the 

 River Warren, it began to be drained in that direction, perhaps flowing at 

 first across the watershed between the Poplar and Severn, and later along 

 lower courses, including- the canoe route by the Hill and Hayes rivers. 

 Each of its successive outlets was probably eroded to a considerable depth, 

 being occupied by the outflowing river during the time of formation of two 

 or more beaches, until the retreat of the southeastern border of the portion 

 of the ice-sheet remaining west of Hudson Bay finally permitted ch-aiuage 

 to take the course of the Nelson, the ice-dammed Lake Agassiz being thus 

 changed to Lake Wiimipeg. The northeastern outflow commenced when 

 the lake at the latitude of the south end of Lake Winnipeg stood about 

 1,000 feet above the present sea-level, and it was gradually lowered to 730 

 feet, when the Nelson, between its successive lakes, began to erode the 

 shallow channel of the upper part of its course. 



Inspection of the series of vertical intervals between the successive 

 levels of the lake during its northeastern drainage suggests that proliably 



