484 THE GLACIAL LAKE AGASSIZ. 



portion for about 75 miles, and from 1 foot to 16 inches per mile farther 

 north. Before the lake in Minnesota had fallen below its highest eastern 

 beach in the south half of its explored extent the rise of the land and 

 diminution of attraction of the waning ice-sheet had caused a slightly lower 

 ])arallel beach, three-fourths of a mile to IJ miles distant, to be formed 

 through the northern third of Clay County; and this secondary beach, 

 sometimes double or triple, is observable at several places along the next 

 30 miles northward. At the nortliwest side of Maple Lake definite beach 

 ridges belonging to the Herman stages of Lake Agassiz lie successively 

 about 8, 15, 30, and 45 feet below its highest beach. Yet all these shore- 

 lines were formed while the relative heights of the land and the lake 

 continued stationary or with only slight change, not sufficient for the 

 formation of any secondary beach ridge, along a distance of some 75 miles 

 northward from Lake Traverse and Herman. 



The Norcross beaches in Minnesota have been explored and their 

 height measured through the same extent of 140 miles, in which the upper 

 Norcross beach ascends northward. about 65 feet by a slope that increases 

 slightly from south to north, averaging nearly 6 inches per mile. In like 

 manner the northward ascents of the Tintah, Campbell, and McCauleyville 

 beaches in Minnesota, and of the lower beaches formed on this east side of 

 the lake during its outflow to the northeast, show a gradual decrease nearly 

 as on the west in North Dakota and Manitoba. 



But comparison of the western and eastern shores i-eveals another very 

 interesting feature of the levels of this glacial lake, namely, an ascent from 

 west to east similar to that from south to north, but of less amount and 

 diminishing in a similar ratio between the successive stages of the lake. 

 On the latitude of Larimore and Grand Forks the ascent of the highest 

 Herman stage of Lake Agassiz above a line now level is approximately 

 33 feet in about 70 miles from west to east, the rate per mile being very 

 nearly half as much as froni south to north; and in the later Herman 

 stages it is diminished to about 30, 25, and 20 feet. On the Norcross 

 shore-lines this ascent toward the east is approximately 10 feet in about 60 

 miles, and it is reduced in the McCauleyville stages to only 3 or 4 feet in 

 about 50 miles; yet it continues through all these stages approximately half 



