2887.} 445 [Upham. 



to the Leaf Hills moraine. At the west end of the Leaf Hills and 

 thence through a distance of fifty miles northward, this stage of 

 recession carried the ice-border back only five to ten miles \ and in 

 the main Leaf Hills, as before noted, the two moraines are united. 

 Across the Mississippi basin the glacial recession between them 

 uncovered an area mainly twenty to forty miles wide. The por- 

 tion 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 Al- 

 exander, in northwestern Morrison county, only twenty miles dis- 

 tant. There, as in the Leaf Hills, this moraine and that of Fergus 

 Falls come together. Ascending 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 north- 

 west side in passing north-northeastward 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 modified drift were 

 probably wholly deposited north of Little Falls. Later moraines, 

 formed at times of halt or re- advance, interrupting the recession of 

 the ice-sheet between northern Minnesota and Hudson bay, have 

 not been determined, but I believe that they exist and await dis- 

 covery when the glacial drift of that wooded and very scantily in- 

 habited 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 successive stages of the lake, probably find their expla- 

 nation 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 Red river 

 valley between Fargo and Grand Forks, and extended northwest- 

 erly across northern Dakota, as shown by its moraines remarkably 

 developed along the south side of Devil's lake and onward to Tur- 

 tle mountain. Toward the east, the ice-sheet at this time had 

 receded from the southwest part of lake Superior, which was 

 held about 500 feet higher than now and overflowed to the Saint 

 Croix and Mississippi rivers by the way of the Bois Brule river 

 and Upper Saint Croix lake. It seems nearly certain also that the 



