62 PHYSICAL GEOGEAPHY. 



valuable nor so numerous as they are on many of the other 

 rivers of the eastern system. 



Iowa fixer. The Iowa river rises in Hancock county, in 

 the midst of a broad, fiat, or slightly undulating drift-region. 

 The first rock exposed in its valley is the sub-carboniferous 

 limestone, which occurs in the form of rocky banks to the 

 stream in the southwestern corner of Franklin county. The 

 river then enters Hardin county, and cuts across the north- 

 eastern corner of the Iowa coal-field in a southeasterly 

 direction, and enters the region of the sub-carboniferous 

 limestone again, which it crosses, continuing in the same 

 direction, and enters the region of ttie Devonian strata near 

 the southwestern corner of Benton county. It continues in 

 the region occupied by the Devonian rocks all the way to its 

 confluence with the Cedar, having made an abrupt bend to 

 the southward in the northern part of Johnson county. 

 From the point of its confluence with the Cedar it is known 

 to traverse a part of the region occupied by the sub- 

 carboniferous strata, but they being the friable ones of the 

 Kinderhook formation, no exposures of them are to be seen 

 along that part of its course. Below its junction with the 

 Cedar, and for some miles also above that point, its valley is 

 broad and flat, especially upon its northern side. Bluffs 

 of from one hundred to one hundred and fifty feet in height, 

 border the southern side of the valley, near the foot of 

 which the river runs until it enters the flood-plain of the 

 Mississippi. 



Above the point just named the valley is generally broad, 

 with gently sloping sides, seldom too steep to be readily 

 cultivated, and everywhere very beautiful if not romantic. 

 The exposures, along its course, of the sub-carboniferous and 

 Devonian limstones are usually in the form of low cliffs or 

 smaller ledges, and long distances often occur without an 

 exposure of rock of any kind to be seen, for the whole valley 

 is covered with excellent soil and deep subsoil derived from 

 the drift which profusely covers the whole region. The 

 valley has generally a well-marked flood-plain, and more or 



