170 ARTIFICIAL LEVEES. [CHAP. XXX. 



being seen at a and b. The banks are higher than 

 the bottom of the swamps, f g and d e ; because, 



Section of channel, bank, levees (a and b), and swamps of Mississippi 



River. 



when the river overflows, the coarser part of the sedi 

 ment 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 receive its vast burden of water and 

 mud : and if it went to Lake Pontchartrain, it would 

 have to excavate a new valley like a b c, many times 

 deeper than the bottom of that lagoon. 



The levee raised to protect the low grounds from 

 inundation, was at first, when we left New Orleans, 

 only four feet high, so as not to impede our view of 

 the country from the deck ; but as we ascended, both 

 the natural bank and the levee became higher and 

 higher, and by the time we had sailed up sixty-five 

 miles, I could only just see the tops of tall trees in 

 the swamps. Even these were only discernible from 

 the roof of the cabin, or what is called the hurricane 

 deck, when we had gone 100 miles from New 

 Orleans. 



