Age of the St. Croix Dalles — Upham. 349. 
direction thence through central and northern Minnesota. 
This principal interlobate line or belt was similar to those 
lying in succession between the Superior, Chippewa, Green 
Bay, Michigan, and more eastern lobes of the very broad 
Laurentide part of the continental glacier, as mapped by 
Prof. T. C. Chamberlin.* 
\\ hy the Keewatin glacial currents were finally 
stronger than those from the Lake Superior region, pushing' 
them back or overriding a part of that ice lobe, I have ex- 
plained by the climatic conditions attendant on the pro- 
gressive melting of the ice borders mainly from southwest 
to northeast and from west to east, enabling the gray drift 
to spread over the red drift on the east side of the Keewatin 
lobe, in eastern Minnesota, from St. Paul northeast and 
north to Taylor's Falls and Rush City.t 
2. It was suggested by Moses Strong, of the Wis- 
consin Geological Survey, that the St. Croix, or more prob- 
ably a branch of it, may formerly have flowed through the- 
ravine, about three-fourths of a mile east of the Upper 
Dalles, in which the railroad runs south from the station 
of St. Croix Falls, that channel being abandoned when 
the present channel in the Dalles became deep enough, 
through erosion, to carry all the water. J 
Berkey and Elftman, in their papers before cited, argue 
that the preglacial upper part of the St. Croix passed west 
of the Dalles, the former regarding it as probably tributary 
southwestward to the Mississippi, and the latter tracing its 
course in coincidence with the Sunrise river and Chisago 
lake to rejoin the present St. Croix valley farther south. 
Mr. Rollin T. Chamberlin thinks that the preglacial 
St. Croix river, flowing past the site of the Dalles in the 
channel mentioned by Strong, may have continued past 
Dresser Junction, and along Horse creek valley to the Ap- 
ple river, which lower down empties into the present St. 
Croix. 
* Geolog>^ of Wisconsin, vol. i, as before cited; U. S. Geol. Survey, 
Third Annual Report, for 1881-82, pi. xxviii, and Seventh Annual Re- 
port, for 1885-6, pi. viii. 
t Changes in Currents of the Ice of the Last Glacial Epoch in East- 
ern Minnesota, Proceedings of the Am. Assoc, for Auv. of Science, 
vol. xxxii, for 1883, pp. 231-234; Geology of Minnesota, vol. ii, 18S8, pp, 254- 
256, 409-417, 463, 603-605. 
t Geology of Wisconsin, vol. ill, 188(i, p. 416. 
