664 THE ICE AGE ZzV NORTH AMERICA. 



back only five to ten miles ; and in the main Leaf Hills, as 

 before noted, the two moraines are united. Across the Mis- 

 sissippi basin the glacial recession between them uncovered 

 an area mainly twenty to forty miles wide. The portion of 

 the ice-sheet nearest to Little Falls at the time of the Leaf 

 Hills moraine was in the vicinity of Fish- Trap Lake and Lake 

 Alexander, in northwestern Morrison county, only twenty 

 miles distant. There, as in the Leaf Hills, this moraine and 

 that of Fergus Falls come together. Ascendiug the Mississippi, 

 a distance of eighty miles intervened between Little Falls and 

 the ice-border at the time of the Leaf Hills moraine, which 

 extends approximately parallel with the river and ten to twenty 

 miles from it on its northwest side in passing north-northeast- 

 ward from Morrison county. 



During the formation of the tenth or Itasca moraine, and 

 of the eleventh or Mesabi moraine, crossing the lake region at 

 the head of the Mississippi, the gravel and sand of the modi- 

 fied drift were probably wholly deposited north of Little Falls. 

 Later moraines, formed at times of halt or read van ce, inter- 

 rupting the recession of the ice-sheet between northern Minne- 

 sota and Hudson Bay, have not been determined, but I believe 

 that they exist and await discovery when the glacial drift of 

 that wooded and very scantily inhabited region shall be fully 

 explored. The many beaches of Lake Agassiz, all showing an 

 ascent northward when compared with the level of the present 

 time, but with this ascent gradually decreased during the suc- 

 cessive stages of the lake, probably find their explanation in 

 the manner of retreat of the ice in Canada, interrupted there, 

 as farther south, by pauses and the formation of moraines. 



Contemporaneously with the deposition of the glacial flood- 

 plain at Little Falls and the accumulation of the Leaf Hills, 

 the ice-front forming the north shore of Lake Agassiz crossed 

 the Eed River Valley between Fargo and Grand Forks, and ex- 

 tending northwesterly across northern Dakota, as shown by 

 its moraines remarkably developed along the south side of 

 Devil's Lake and onward to Turtle Mountain. Toward the 

 east, the ice-sheet at this time had receded from the south- 

 west part of Lake Superior, which was held about five hundred, 

 feet higher than now and overflowed to the St. Croix and 



