Interglacial Chronometer. — Winchell. 73 
This is also the most frayed and smoothed off with age and surface 
disintegration, thus becoming wider and less distinct. 
In 1680, when father Hennepin, the discoverer of the falls of 
St. Anthon}', taken liy the Sioux Indians in the vicinity of La 
Crosse, was led in captivity to lake Mille Lacs, the source of 
the (then) St. Francois river, they left the Mississippi at St. Paul 
and apparently followed this route to avoid the rapids and falls of 
St. Anthony ; for in this valley are several lakes and from them 
flows a canoeable stream to the Mississippi again, northward. 
There is a significant break-down and total lack of the Trenton 
limestone at St. Paul on the left bank, just above Dayton's bluff, 
for a distance of nearly a mile. This break-down occurs on one 
side of the right angle which the river there makes, and directl}' 
where the course of the present river-channel below, if extended 
northwestward without the right-angled turn, would encounter the 
bluff. This fact alone is significant of changes in the course of 
the gorge of the Mississippi as occupied and eroded at different 
epochs in the past. On following up this intimation, the inquir- 
ing geologist ascertains that there is not only no known existence 
nor any sign of the Trenton limestone anywhere northwestwardly, 
and that the St. Peter sandstone a lower stratum occurs in out- 
crop in the low grounds intervening between the mouth of Trout 
l)rook and the mouth of Rice creek, but also that on either side, at 
a short distance, the Trenton still exists. On the southwest side 
it rises into a conspicuously hilly tract, and includes some of the 
highest beds belonging to this formation known in this part of 
the state. On the northeastern side it is less prominent, occur- 
ring so far as known, mostlj' as remnants of the outrunning fringe 
of the formation. But still further east, across a wider valley, a 
conspicuous spur of the higher beds of the Trenton shoots off 
northeastwardly, diverging from St. Paul and passing into Wash- 
ington county at Castle. This shows that at some former time 
there was a great vallej' northward from St. Paul, whose east and 
west sides diverged from the break-down in the Trenton which 
has been mentioned. One portion of this great valley, lower now 
than the rest, extends northwestwardly to the mouth of Rice's 
creek and there encounters the present Mississippi river six miles 
above the falls of St. Anthony. In this poitiou of this vallej" lie 
McCarron, Bennett, Josephine, Johannah and Long lakes, con- 
nected with the Mississippi, either toward the north or toward the 
