132 CREVASSES AND INUNDATIONS. [CHAP. XXX. 



towers of New Orleans in the distance, they should be hurried 

 into a wilderness, and perish there. 



I was shown the entrance of what is called the Carthage 

 crevasse, formed in May, 1840, and open for eight weeks, during 

 which time it attained a breadth of eighty feet. Its waters 

 were discharged into Lake Pontchartrain, when nothing was 

 visible between that great lagoon and the Mississippi but the 

 tops of tall cypress trees growing in the morass, and a long, nar- 

 narrow, black stripe of earth, being the top of the levee, which 

 marked the course of the river. 



The reader may naturally ask why the Mississippi, when it 

 has once burst through its bank, and taken this shorter cut to the 

 sea, does not continue in the same course, reaching the salt water 

 in a few miles instead of flowing two hundred miles before it 

 empties itself into the Gulf. I may remark in reply, that the great 

 river does not run, as might be inferred from the description of 

 some of the old geographers, on the top of a ridge in a level plain, 

 but in a valley from one hundred to two hundred and fifty feet 

 deep. 



Fig. 9- 



^J?^_jg&amp;gt;jjj._ 



c 

 Section of Channel, Bank, Levees (a and b), and Swamps of Mississippi River. 



Thus a b c may represent the cavity in which the river flows, 

 the artificial levees at the top of the banks being seen at a and b. 

 The banks are higher than the bottom of the swamps, f g and 

 d e ; because, when the river overflows, the coarser part of the 

 sediment is deposited at a and b, where the speed of the current 

 is first checked. It usually runs there with a gentle current 

 among herbage, reeds, and shrubs ; and is nearly filtered of its 

 earthy ingredients before it arrives at the swamps. It is probable 

 that the Mississippi flows to the nearest point of the Gulf, where 

 there is a sufficient depth or capacity in the bed of the sea to 



