2i6 
lOWA ACADEMY OP SCIENCES 
and gravelly, and in many places show some signs of assortment of 
material approaching stratification. Gravel banks and sand banks, well 
stratified, are shown at the top of all the higher hills in the drift. The 
crests of the conical hills are crowned with caps of small boulders and 
cobble stones, so thick-set as to make cultivation impossible. Such hills 
are well shown at the southeast corner of the Fayette County Poor Farm, 
the cemetery being located on the top of the highest one. These facts 
seem to establish a kame — or esker — like nature of the hills and ridges 
of the Iowan border. It is probable that the present elevations in the 
drift surface mark the positions of depressions in an ice sheet of irregu- 
lar surface as it began to melt. The lowest points of these depressions 
received the materials from the melting slopes. All materials were 
washed along except the largest boulders, and somewhat assorted by 
water. Steep kettle-hole depressions in the ice account for the formation 
of the conical hills, with their caps of cobble stones. Long, gravelly 
ridges mark the position of longer depressions with more gentle slopes. 
When the melting had progressed so far that the divides between the 
depressions in the ice had sunk as low or lower than the original 
depressions, the remaining fragments of the ice sheets slowly melted in 
place, depositing the remainder of their detritus without washing or 
assortment, and the accumulated boulders of the earlier stages of melt- 
ing w^ere left lying on the surface of this till. 
Perhaps the most interesting point to the observer in this region is 
the three phases exhibited in the valley of each stream that begins in 
the Iowan drift and fiows outward across the border into the Loess- 
Kansan. 
The first phase, that in the Iowan, is a valley broad and shallow, often 
nearly as wide as long. The contour exhibits no sharp lines. The low, 
convex divides, with gentle undulations, separate the streams, w’hich 
course gently through broadly concave sloughs in which they have done 
very little work since the close of the Iowan ice period. 
The second phase of each valley begins where the wide slough bot- 
tom narrows down to a point from which the stream fiows through a 
small V-shaped gorge trenched into limestone. This stage of each valley 
is narrow with rather steep, but smooth and rounded, sides of limestone 
which stand out clean and unweathered. The narrow floor of each valley 
is in places covered with a thin layer of till, as is well shown just above 
the county bridge four and one-half miles south of West Union. Also 
along the line of the Chicago, Milwaukee & St. Paul Railroad, just above 
where it intersects an unfinished railway grade two and a half miles 
east of Randalia, the drift for a distance of a half mile has almost oblit- 
erated the valley of the stream. But even here low hills of limestone 
are exposed to the east of the stream. In general these valleys are sharply 
defined and little affected by drift deposits. A broad belt of sandy soil, 
flanking at either side this stage of the valleys, is a constant feature. It 
stretches outward from the top of the inner valley for a distance of a 
fourth to a half mile or more. 
