IMPKOYEMENT OF MOUTH OF MISSISSIPPI EIYEE. 85 



tion of the same. The matter is very phiiii Avheii v.-e observe the 

 present working of the river; an abrasion takes place on one side) 

 while a corresponding accretion takes place on the other, and in 

 this manner a constant lateral motion takes place which may con- 

 tinue in one direction for an indefinite period, until from some 

 cause or other the motion is changed. 



It is not difficult to comprehend the movement of an island 

 down stream, or the shifting of the point of bifurcation. The 

 upper end of the island is worn away by the current, while at the 

 same time the lower end grows by deposits which take place in the 

 still water. The movement of beflds, on the other hand, partakes 

 of an entirely different nature; these must be destroyed before they 

 can reform. The peninsula like portion of land projecting into 

 the bend is abraded cm both the upper and lower side, until it is 

 finally cut off, the old river bed is abandoned and a new one is 

 formed; the regimen of the river thus disturbed, at once seeks to 

 readjust itself and hence the fearful inroads consequent upon a 

 natural or artificial cut-off. The causes are plain, the absolute 

 slope, and consequently the velocity is increased, while at the same 

 time the reciprocity of curves is broken, and a new bend must re- 

 sult. The remedy in this case is plainly the preservation of the 

 natural bends. 



My object in dwelling upon the foregoing, although foreign to 

 the subject, was simply to illustrate the source of the material re- 

 quisite to form the delta. The material which is carried along b}^ 

 tlie action of the current, will be found to differ very materially 

 along the course of the stream, on the upper portions it is com- 

 posed of sand and gravel, this will be found reduced by attrition as 

 we descend the river, until it is finally reduced to impalpable mud; 

 decomposed vegetation is added by the draining of the forests, and 

 of this composition the delta is formed. I can give no better illus- 

 tration of the delta than the following from a translation of a 

 work by " Reclus." He says: 



"These narrow embankments of mud, brought dov^^n into the open 

 sea by the fresh water, present a striking spectacle. In several 

 places these banks are only a few yards thick, and during storms 

 the waves of the sea curl over the narrov.^ belt of shore, and min- 

 gle with the river. The soil of the banks becomes perfectly spongy ; 

 it is not firm enough to allov^ even willows to take root, and the 



