130 THE GLACIAL LAKE AGASSIZ. 



line of the western of these ice-lobes coincided nearly with the Red and 

 Minnesota rivers and the njDper Des Moines, its southern end being near 

 Des Moines, in central Iowa. This may be named the Minnesota lobe of 

 the ice-sheet. Farther west the Dakota lobe stretched from the Souris 

 basin and the region of Turtle Mountain south across the east half of 

 North and South Dakota to Yankton, its central line being along the 

 valley of the James or Dakota River. In Manitoba the glacial currents, 

 passing to the Minnesota and Dakota ice-lobes, moved to the south- 

 southeast and south, as noted at several localities on the Winnipeg River 

 above Lac du Bonnet, on Lakes Winnipeg, Winnipegosis, Manitoba, and 

 St. Martin, at Stonewall and Stony Mountain, and on the Assiniboine; 

 and these currents are remarkably contrasted with the southwestward 

 striae of the contiguous region of the Lake of the Woods and the country 

 extending thence east and north. These converging striae in western 

 and eastern Manitoba probably were engraved mostly during the reces- 

 sion of the glacial boundary, when Lake Agassiz was extended over the 

 greater part of the Red River Valley. On the east this lake appears 

 to have been bounded by a vast ice-lobe outflowing from the region of 

 Lake Superior and James Bay southwest and south to the Lake of the 

 Woods and Lake Itasca, representing the earlier convergent ice-lobes of 

 the northeastern and of the western and southern portions of Mimiesota, 

 while on the west it was bounded by the representative of the Dakota 

 ice-lobe, then outflowing from the region of Lake Manitoba and Riding 

 Mountain southward to the terminal moraine of Pilot Knob, the north 

 side of Devils Lake, Turtle Mountain, and the Tiger, Brandon, and 

 Arrow hills. 



1 Trmisportatlon of bowlders. — Nearly everywhere the greater part of the 

 drift is derived from formations not far distant, varying from a few miles 

 to 25 or 50 miles away, in the direction from which the ice-sheet moved; 

 but mingled with this material from comparatively near sources are other 

 portions, both of the fine detritus and of the small and large rock masses, 

 which have been transported longer distances, as the Archean bowlders of 

 northern Montana and the upper Saskatchewan district, derived from the 

 Archean belt east and north of Lake Winnipeg and about Reindeer Lake. 



