lxviii FISHES OF ILLINOIS 



vegetation can grow. Here Nuphar, Nymphcea, Potamogeton, 

 and the limnophilous species of filamentous algae abound. In 

 dry weather the visible flow may almost cease in places, and in 

 flood a full stream may fill the banks even to overflowing; but it 

 is never quite a rushing muddy torrent, nor ever quite a dry 

 creek with scattered pools floored with gravel or naked clay. 



Cache River 



Cache River drains the eastern part of Union county, the 

 southwestern half of Johnson count3 T , the northern part of 

 Massac county, and most of Pulask and Alexander counties. 

 The edges of this basin are not clearly defined, but it probably 

 covers an area of about 623 square miles. It lies entirely in 

 the driftless area which covers the southern point of Illinois, 

 just south of the Ozark ridge. The basin is very largely made 

 up of alluvial bottom-lands which border all the streams, and 

 which in southern Alexander county extend entirely across the 

 state from the Cache River to the Mississippi. These bottom- 

 lands are generally flat, and are interspersed with cypress ponds 

 and marshes, being mostly too wet for cultivation without a 

 very thorough system of drainage. They are subject to annual 

 inundations from the floods of the rivers, and are generally 

 covered with timber, now being rapidly removed for lumber. 

 The most elevated portions of these bottom-lands, however, 

 have a light, rich, sandy soil, very productive when cultivated. 

 Farther from the streams, the surface of the country is roughly 

 broken. 



The Ohio River may, at one time, have discharged wholly 

 or in part through " Cache valley," which crosses southern 

 Illinois a few miles north of its present course. Its point of 

 connection with Cache valley is immediately north of Metropolis, 

 where for a distance of 4 to 5 miles a clay deposit has accumu- 

 lated in the line of the old valley. The surface of this clay 

 deposit stands only about 75 feet above the present stream, and 

 is much lower than the surface of the Tertiary deposits on either 

 side. It is not known as yet, whether the channel formerly 

 constituted the sole line of discharge for the Ohio or not. 

 Possibly the river divided its waters between the Cache and its 

 present channel. The bluffs of the powerful stream which 

 excavated the valley of the Ohio extend from the Mississippi 

 half-way across Alexander county, and then turn northeast, 



