Rocky Mountains. 41 



the low country, which extends west to the Mississippi. It 

 is characterized by the great extent of the river alluvion, the 

 increased width and diminished velocity of the stream. The 

 river banks are low, but thickly wooded with sycamore, cot- 

 ton wood, river maple, the planeraaquatica, cypress, &c. The 

 river hills, which terminate the alluvial district, are distant 

 and low, and it often happens that the surface descends on 

 both sides, from the immediate banks of the river to these 

 hills. Hence when the waters of the river are sufficiently 

 swollen to flow over its banks, they inundate extensive tracts, 

 from which they cannot return to the channel of the river, 

 and are left stagnant during the summer months, poisoning 

 the atmosphere with noxious exhalations. Many of these in- 

 undated tracts have a soil of uncommon fertility, which it is 

 probable will hereafter be recovered from the dominion of 

 the river, by dykes or levees. 



The beach or sloping part of the immediate bank of the 

 Ohio, throughout its whole extent, is of rather -gradual as- 

 cent, and covered with timber a considerable distance below 

 high- water mark. The average rapidity of the current of the 

 Ohio is about two and an half miles per hour, and the de- 

 scent of its surface nine inches per mile, as estimated by Dr. 

 Drake of Cincinnati. The annual inundations happen in the 

 spring. The range between extreme hig'i and low vvater, in 

 the upper part of the river, is more than 60 feet; but below, 

 where it is not confined by high banks, it is much less. 



About the falls of Ohio, the cane, (myegia macrosperma 

 of PersoonJ begins to be seen, and increases in quantity 

 thence westward to the Mississippi. The " Cave inn Rock," 

 or " House of Nature,'' which we have before mentioned, is 

 an immense cavern, penetrating horizontally into a stratum 

 of compact limestone, which forms the river bank for some 

 distance above Golconda in Illinois. Its entrance is a large 

 and regular arch, placed immediately on the brink of the ri- 

 ver, and a similar form is preserved in some degree through 



vol. i. t> 



