54 
IOWA ACADEMY OP SCIENCES. 
changes, based on the succession of strata within the county, 
may be represented in the on following diagram: 
Fig. 3. Diagram representing the relative positions of the shore lines as indicated hy 
the general character of the strata within Madison county. 
Note.— A later comparison of outcrops proves that those shales in the upper Des 
Moines which are mentioned in this paper as calcareous, lie a few feet above those to 
the east with which they were compared; hence the local evidence mentioned that 
the upper part of the Des Moines shales becomes calcareous toward the west is want- 
ing.— Author. 
DRIFT SECTION AT OELWEIN, IOWA, 
BY GRANT E. PINCH. 
Just outside the limits of the growing town of Oelwein, Iowa, 
to the southeast, the Chicago Great Western Railroad company, 
in order to lessen a troublesome grade, have excavated a cut 
nearly a mile in length. At the end farthest from the town, 
where it passes diagonally through a lidge, it has a maximum 
thickness of thirty-two feet. This ridge has a northwest- 
southeast trend, and is one of the ordinary gentle swells char- 
acteristic of the drift of this region. 
To pass along the front of so extensive a section, twice the 
depth of ordinary drift cuts, fresh and untarnished by sun and 
rain, is a pleasure to any one, whether geologist or not. The 
great variety of colors — strata black, brown, gray, blue, green, 
and several shades of yellow; the distribution of boulders like 
plums in a Christmas pudding; the intricate twistings and 
turnings of some layers and the unexpected, fantastic intrusion 
of others, all could not help but hold the eyes of both trained 
and untrained observers. 
Though of great interest throughout its entire length, the 
section exposed where the cutting pierces the before-mentioned 
