THE TOPOGRAPHY AND HYDROGRAPHY OF ILLINOIS lxiii 



with a fall of about 60 feet. North Fork in the first mile of its 

 course has a fall of about 30 feet. In the remaining 35 miles a 

 descent of about 60 feet is made. The banks of this stream are low 

 and subject to frequent overflow. In southeastern Hamilton county 

 the course of the North Fork is entirely lost for about 3 miles as it 

 crosses a swamp. 



The course of the main stream is crooked and the current 

 sluggish, with long stretches of quiet water where soft black ooze 

 can accumulate year after year, and where a typically lacustrine 

 vegetation can grow. Here Nuphar, Nymphcsa, Potamogeton, and 

 the limnophilous species of filamentous algas abound. In dry 

 weather the visible flow may almost cease {h 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 IJfnion county, the south- 

 western half of Johnson county, the northern part of Massac county, 

 and most of Pulaski and Alexander counties. The edges of this 

 basin are not clearly defined, but it probably covers an area of about 

 600 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 dis- 

 tance of 4 to 5 miles a clay deposit has accumulated 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 



