24 
IOWA ACADEMY OF SCIENCES. 
In 1888, Calvin* first called attention to this channel in dis- 
cussing the deep well put down at Washington. This old valley 
has at this point been cut down 350 feet below the present sur- 
face, or to 419 feet above sea level. It has been cut almost 
entirely through the Kinderhook; and the base is 285 feet below 
the nearest outcrops of rock (Augusta) on Crooked creek, or 324 
feet below the higher rock surface underlying the prairies near 
Keota. At Washington there is no definite evidence bearing on 
its width. 
In the northwestern corner of the county evidence of a simi- 
lar erosion is seen. In passing up English river the sharp bluffs 
of indurated rocks abruptly disappear. The bottom land 
expands on the south to a width of a mile and half or more. It 
is bordered by gently rounded hills of drift rising sixty to 
seventy feet above the river, or to an elevation of about 800 
feet. This bottom land extends some six miles, when the hills 
close in on the river, and within a short distance a rock outcrop is 
found. A number of wells have been bored on the top of these 
drift hills, some being carried 100 feet or more below the level 
of the river, and yet in no case has the underlying rock been 
encountered. 
In the southeastern portion of the county, near the great 
bend in Crooked Creek, similar relations obtain. There is the 
same marked absence of rock outcrops, the same soft drift 
topography, and the numerous deep wells, drawing their supply 
of water from deeply buried gravel beds. 
In the region near Deep River, in Poweshiek county, the 
limestone surface is usually encountered about 200 feet below 
the general level of the drift upland, and yet one boring was 
carried to a depth of 450 feet, or to within about 460 feet of sea 
level, before encountering rock. There is thus evidence in this 
region of a broad and deep channel lying at a level of between 
300 and 400 feet below the present surface, and running in a 
northwest - southeast direction. 
Towards the southeast the evidence of such buried channels 
becomes more and more abundant. In Des Moines county, near 
Kossuth, a channel has been found, the base of which lies 342 
feet below the present surface, or 274 feet above tide. A short 
distance west of Sperry two wells have been driven 360 feet to 
rock, while neighboring wells encountered the limestone at from 
*Am. Geol., I, 23-31. Minneapolis, 1888. 
