420 W. UPHAM ESKER NEAR AVINNIPEG, MANITOBA 



in this respect that have been made known in the extensive literature of 

 glacial geolog3^ 



■ Apparently a readvance of the ice-front from the north and west to 

 an extent of about 1,000 feet beyond its former place, along this distance 

 of about 1 mile, satisfactorily accounts for these sections of till above 

 the esker gravel and sand. Such oscillation of the ice-wall required possi- 

 bly only two or three summers, but more likely the summers of a decade, 

 more or less, averaging a little cooler than the preceding and following 

 years of relatively rapid wane and withdrawal of the ice-fields at the end 

 of the Glacial period. The thin gravel beds at the surface above much 

 of the till sheet may have been formed a few j^ears later, when the pre- 

 viously onfiowing border of the ice was melting away. 



In passing we may add that the whole duration of Lake Agassiz in 

 this basin of the Eed Eiver and Lake Winnipeg, with retreat of the ice 

 boundary across the 1,000 miles from western Minnesota to Hudson Bay, 

 appears to have measured only about a thousand ^^ears, as estimated from 

 the amount of its wave erosion and beach sand accumulation, in compari- 

 son with the much greater amount of similar work done by Lake Michigan 

 and others of the Great Lakes of the Saint Lawrence Basin since the 

 Ice Age. As a very small part of that time of duration of the glacial 

 lake and departure of the ice-sheet from its area, we may reasonably 

 infer that the time occupied in the accumulation of the kames and esker 

 near Winnipeg must have been short, probably not exceeding 20 or .30 

 years. 



Depth of the Esker shown by Wells 



To provide water for the workmen in the excavation, a well 45 feel: 

 deep had been dug or bored at its bottom about a half mile from Birds 

 Hill Station before my visit in 1887. It was wholly in the same forma- 

 tion of gravel and sand, showing for this deposit there a thickness of 

 about 90 feet below the crest of the esker, or some 40 or 50 feet below 

 the general level of the fiat valley plain. 



Again, about a third of a mile farther east a second well, recently dug 

 or bored for the workmen of the Winnipeg pit, goes down below that pit 

 40 feet in the same stratified drift to water. Like the preceding well, it 

 gives a depth of 90 feet for the esker deposit. The important and very 

 significant feature thus proved is that the fluvial gravel and sand con- 

 tinue about 40 feet lower than the level of the surrounding country. As 

 will be more fully explained on later pages, this implies that a very large 

 part of the general drift-sheet was material contained in the ice-sheet, 

 borne along by it above the subglacial land. 



