544 GREAT DEPTH OF THE MISSISSIPPI. 



ships entering the Mississippi, but the moment that a 

 vessel is inside the bar she is in deep water, quite 

 four or five times the depth of that on the bar. * 



Sir Charles Lyell in his remarks upon Mississippi 

 phenomena notices the fact, that strikes every observant 

 traveller, that the Mississippi is a river having a nearly 

 uniform breadth from its mouth to St. Paul, a distance 

 of 2000 miles from the sea, and Sir C. Lyell asserts 

 that this majestic river for considerable sections of its 

 course cuts a bed for itself out of the soil to a depth 

 of more than 200 feet below the top of the bar, which 

 obstructs its entrance to the sea. f 



The depth of portions of the channel of the Missis- 

 sippi is often very great, sometimes even amounting 

 to as much as 250 feet, while at other points obstruc- 

 tions occur which seriously impede the safe navigation 

 of the river, owing to the fact that throughout its 

 great alluvial plains-track the stream is continually 

 shifting its course. Steamers ascending or descending 

 the river must therefore be guided by river pilots, 

 who have intimate local knowledge of these changes, 

 as banks frequently form, which sometimes entirely 

 close the old channel, while the current rapidly exca- 

 vates a new one in another place. A large number 

 of changes occur in this way every season and require 

 constant watching by specially trained pilots, especially 

 upon the Missouri. 



Another of the dangers incident to navigation on the 

 Mississippi-Missouri system is that arising from what 

 are known as "snags." 



* Physical Geography of the Sea, by Lieut. M. F. Maury, U.S.N., 

 1 6th Edition, 1877, p. 190. 



y Principles of Geology, by Sir Charles Lyell. Edition of 1867, 

 Vol. i., pp. 440 i. 



