o02 The American Geologist. xovcnib.i-. iwt> 
raiiic. there was for a time u great lake formed north of tliis Fox 
ridge divide. It was deep enough to float ice-floes and probably 
bergs from the edge of the ice sheet further north. These 
formed a bouldery beach along the margin, particularly along the 
southern side. Of the two outlets indicated, the western one 
cut down more rapidly, and formed part of the course of the 
Missouri. As erosion proceeded the boulder}^ margin I)ecame a 
ridge, because it^'ielded less rapidly to degradation than the soft 
clays and loose sands adjacent. 
For this glacial lake we propose the name lake Arikaree, after 
the Indian tribe whose home formerly occupied a considerable 
portion of its ai'ea. 
EDITOEIAL COMMENT. 
An lNTER(iLACIAL CHRONOMETER; A CORRECTION. 
In an article in the August number of the (tEologist (1802), 
entitled "An Approximate Interglacial Chronometer," is an ol)- 
vious error. It is plain to anyone who carefully studies the 
map given on plate v[ that the '• interglacial gorge " which is 
represented to extend from the mouth of Bassett's creek, on the 
west side of the river, to the mouth of Nine-mile creek, .should 
be continued, and actually was continued, further north wanl. and 
to the mouth of Rice creek, where the •• pre-glacial gorge" is 
represented to begin. If the interglacial erosion l)egan l)ecause 
the first glacial epoch displaced the river from any portion of its 
bed, the gorge that was the result of such interglacial erosion 
must have begun where the displacement l)egan. The displace- 
ment began at the mouth of Rice creek, at that time, and not at 
the mouth of Bassetts creek. This will make the interglacial gorge 
extend, as the Trenton limestone is known on each side of the river 
to extend, to near the mouth of Rice creek, increasing the result 
that expresses interglacial time to about fifteen thousand years. 
It was an oversight in the calculation, due to the use of an old 
map showing the gorge through the western limits of Minut'npo- 
lis made in discussing the post-glacial recession of the falls of 
St. Anthony. The reader should understand the dotted lines 
that outline the interglacial gorge to be continued northward to 
the point where the pre-glacial gorge begins, and should sul)sti- 
tute 15,000 years for 9,750. 
