1s4 The American Geologist. March, 1892 
miles below, and easily seen from the hights at Keokuk, are War- 
saw on the Illinois side, and Alexandria in Missouri. The former 
is of interest as being the home of A. H. Worthen, whose labors as 
state geologist of Illinois placed him in the foremost rank of scien- 
tists. The name,Gate City, was applied to Keokuk in the old days 
of prosperous river traftic, when its position at the head of naviga- 
tion made it the ‘‘entering port” of much of Lowa’s commerce. 
Topography.—The thickness of the surface deposits is not 
such as to materially affect the topographical features of the re- 
gion, and hence these derive their significance largely from the 
subjacent rock surface. A high mural escarpment faces the river 
along the eastern and southern sides. In places this wall is con- 
siderably reduced and toward the south is intersected by the nar- 
row valley of Soap creek, leading in from the northwest. Near 
the lower lock, the escarpment rises in bold outlines, with retreat- 
ing summit, to a hight of one hundred and sixty feet. Farther 
to the north, the bluff presents a steeply sloping face covered 
with superficial deposits. On the south, the escarpment is bold 
and conspicuous, rising to a hight of nearly two hundred feet, 
its face irregularly scalloped by narrow and short ravines. The 
highest points at the north and south are capped, underneath the 
Quaternary, by Coal Measure deposits, while between these points 
varying portions of the underlying rock have been removed by 
pre-glacial erosion. Patches of the St. Louis beds still crown the 
bluff at places north of Main street, while at its foot, erosion has 
extended to the Geode formation of the Keokuk beds. A drain- 
age basin occupies the interior of the city north of Soap creek, 
and opens into the valley of that stream a little above its mouth. 
In this area the rocks above the Geode formation have been largely 
removed, leaving an amphitheatre-like depression, partially filled 
by subsequent deposits. These have suffered considerable de- 
nudation, however, since the time of their deposition. Toward 
the northwest, the surface gradually rises to the narrow undula- 
tory plateau forming the divide between the drainage systems of 
the Mississippi and Des Moines rivers, and broadly scalloped on 
either side by subsidiary drainage basins. At Montrose, the 
blutf recedes from the river, leaving a belt of high bottoms three 
or four miles wide between this point and Fort Madison above. 
Beds of sand and gravel are here found twenty to thirty feet above 
the present high-water level of the river. Between this point 
