298 TJic American Geologist. May, loco 
been undertaken; but Mr. Nutter states that lake Calhoun is 
found to have a depth of 40 feet within 500 feet from its south 
shore. Lake Harriet is reputed to be the deepest of the ser- 
ies, and is said to have maximum soundings of about 80 feet. 
When the ice border receded from this line, masses of the 
ice, which had projected as promontories on the sites of the 
lakes, appear to have been left as vmmelted remnants in front 
of the receding boundary, forbidding the lake basins to be 
filled with gravel and sand while the plains, plateaus, and esker 
or kame hills at their west sides were accumulated. 
COMPARISON WITH OTHER LAKE CHAINS IN MINNESOTA. 
hi Marti?i comity. Beside the conditions thus far set 
forth as the causes of this chain of lakes, it is probably true 
that the interglacial gorge of the Mississippi, as studied out 
by Winchell, passing along this course, was one of the rea- 
sons for the deficiency of the drift to fill these hollows and 
consequently for the ice masses left while the modified drift 
adjoining them was laid down. We cannot, however, ascribe 
to the previous gorge the whole or even the chief agency in the 
origin of the lakes. They dififer from the even more remark- 
able chains of lakes in Martin county, adjoining the south 
boundary of this state; for there the three lake series run 
transversely across the course of marginal moraines and of the 
retiring ice border, they are deep hollows in a region of till, 
with no important modified drift deposits, and they seem clear- 
ly referable altogether to failure of the latest drift to fill and 
obliterate interglacial river courses.* 
In Croiu Wing, Cass, a7id Hubbard counties. The analogues 
of this lake chain are found in areas of modified drift in Crow 
Wing, Cass, and Hubbard counties, where lakes tributary to 
Gull and Pine rivers and to Crow Wing river occur in two in- 
structive series, parallel with marginal moraines of the region, 
and attributable to the same causes as are here presented in 
explanation of the Minneapolis lake series. t 
*Geology of Minnesota, Final Report, vol. i, 1884, pp. 479-485. 
tGeology of Minnesota, Final Report, vol. iv, iSgg, pp. 76, 'j']. 
