138 DAVENPORT ACADEMY OF SCIENCES. 



on the "Physiography of Iowa," by Professor Samuel Calvin, 

 State Geologist of Iowa : ^ 



' 'The state is simply an extensive plain— over large areas a very 

 monotonous plain — lying between the great rivers and rising but 

 little above them at any point. The relief is small. The zero 

 point on the river gauge at Keokuk has an elevation above tide 

 of 477 feet; the elevation at Sibley, the highest important railway 

 station in Iowa, is 1,572 feet. It is probable that Ocheyedan 

 mound or some of the morainic prominences in Osceola county 

 rises 100 feet higher than Sibley, l)ut even then there is less than 

 r,20o feet of difference between the lowest and the highest points 

 in the state. 



"On the eastern border of the state the Mississippi flows in a 

 gorge, which at New Albin and Lansing, measured from the sum- 

 mit of the bluffs facing the valley, is 400 feet in depth. . . The 

 depth of the Mississippi gorge diminishes toward the south. The 

 valley of the Mi,s.souri is very different from that of the Missis- 

 sippi. It is bordered by a series of high bluffs unique in appear- 

 ance, and more unique in structure, for they have been built up 

 largely of fine dust transported by the winds. The constantly 

 shifting meanders of the stream and the great width of the allu- 

 vial flood plain are among the striking characteristics of this 

 peculiar valle3^ 



" Another of the larger topographic features is the great water- 

 shed. This is the ill-defined ridge which extends in a sinuous 

 course from Dickinson county to Wa3'ne and forms the line of 

 parting between the waters flowing to the Mississippi on the one 

 side and to the Missouri on the other. The watershed is in 

 realit}' the southward extension of the noted ridge of the Dako- 

 tas and southwestern Minnesota, known as the Coteau des 

 Prairies. An area somewhat greater than two-thirds of the 

 state lies east of the watershed; less than one-third lies on the 

 west. 



" On the basis of the effect produced by the great ice sheets of 

 the glacial epoch, the surface of Iowa may be divided into two 

 parts, to be known respectively as the Driftless Area and the 

 Drift-covered Area." 



The Driftless area covers only a small area — Allamakee and 

 portions of Winneshiek, Fayette, Claj^ton, Dubuque, and Jack- 

 son counties. It is a land of thin .soils, high, rocky precipices, 

 long, steep hills and deep rock-cut valleys. The Drift-covered 

 area occupies much the larger portion of the state. It presents 

 four well-defined areas, each having at the surface a sheet of drift 



I. .A.tlas of the State of Iowa. Published under the direction and supervision of M. 

 Huebinger, C. E. By the Iowa Publishing Co., Inc. Davenport, Iowa. 1904. P. 25S. 



