BEACHES OBSEEVED BY ME. TYEEELL. 217 



these outlets ma}' have flowed to the east and south, passing along the 

 margin of the receding ice into Lake Superior, and thence into the Missis- 

 sippi by the way of the Chicago outlet of the glacial Lake Warren, as 

 Prof J. W. Spencer has named the confluent glacial lake wliich is now 

 reduced and separated into parts as the five great lakes of the St. Law- 

 rence. After tlie glacial melting had proceeded so far as to open the great 

 area of Hudson and James baj's to the entrance of the ocean, Lake Agassiz 

 was tributary for some time to this .inland sea by outlets higher than the 

 Nelson River, while the ice-sheet west of Hudson Bay was withdrawing 

 northward. 



Some of the lowest and latest stages of Lake Agassiz during its de- 

 crease as it was drained away by its northeastern outlets, each in succes- 

 sion lower than the preceding, are shown by Mr. J. B. Tyrrell's observations 

 of beaches on Kettle Hill close south of Swan Lake, on the portage 

 between Lake Winnipegosis and Cedar Lake, and in the vicinity of the 

 Grand Rapids of the Saskatchewan.^ Between the time of formation of 

 the Stonewall beach and that of the Xiverville beach the surface of Lake 

 Agassiz was lowered 45 or 50 feet, from a level slightly higher than Lake 

 Winnipegosis to one slightly lower than Lake Manitoba. The former of 

 these levels seems to be represented near the .mouth .of the Saskatchewan 

 by a beach 140 feet above Lake Winnipeg, or 850 feet above the sea.; and 

 the latter becomes apparently double or triple, being represented by three 

 beach ridges, 95, 90, and SO feet above Lake Winnipeg. These beaches, 

 if my correlation as thus stated is correct, are nearly horizontal throughout 

 their observed extent of nearly 300 miles from south to north, and show 

 that the difiPerential northward uplift of the basin of Lake Agassiz was 

 almost completed before the ice barrier was melted back from the area 

 crossed by the Nelson River. 



According to my correlation of the five shore-lines. noted by Mr. Tyr- 

 rell on Kettle Hill, successively, in descending order, 1,070, 1,015, 995, 955, 

 and 920 feet above the sea, the highest belongs to the Hillsboro stage.of 

 Lake Agassiz; the next two to the Emerado stage, there divided because 

 of northward uplifting of the land; while the lower two are, respectively, 



' "Pleistocoue of the Winnipeg Basin," Am. Geologist, Vol. VIII, pp. 19-28, July, 1891. 



