64 PHYSICAL GEOGRAPHY. 



seldom exceed forty feet in height. The valley throughout 

 is broad and shallow, at least in appearance, and its borders 

 are indistinctly denned from the upland. Below the con- 

 fluence of the Shellrock, the drainage area of the river is 

 greatly reduced in width ; at one point in the southwestern 

 part of Linn county, it scarcely reaches ten miles in width. 



Although exposures of the underlying strata are so much 

 more numerous than they are along any other river hitherto 

 described, their cliffs are seldom high, and the stream meets 

 with comparatively little obstruction from them from the fact 

 that its course coincides so nearly with the trend of the 

 formation it flows upon. 



The valley of the Cedar is one of the finest regions in the 

 State, and both the main stream and its tributaries furnish 

 abundant and reliable water power, both as regards constancy 

 of flow and security of mill-sites. 



Wapsipinicon river. This river, in each corresponding 

 portion of its course, is so similar to the Cedar in all respects 

 that it hardly requires a separate description. It rises near 

 where the Cedar does, and runs parallel with and near it 

 along almost its entire course, the upper half of which is 

 upon the same formation — the Devonian. In the northeastern 

 part of Linn county it enters the region occupied by the 

 Niagara limestone, upon which it continues until its con- 

 fluence with the Mississippi. The features produced in its 

 valley by this formation are similar to those produced by the 

 Devonian strata along the upper part of the same valley, and 

 also along the Cedar. 



A striking peculiarity of this stream is the narrowness of 

 the area drained by it compared with its length. It is 

 upward of one hundred and eighty miles long, and the width 

 of its drainage area, in its widest part, is only about twenty 

 miles, and toward the lower portion of its course this area is 

 reduced in some places to ten or twelve miles in width. In 

 consequence of this, the stream is not subject to extravagant 

 floods, and its "mill- sites, which are very numerous, are hence 

 more than usually secure. 



