

s 





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the m; 



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inee ft 

 ilize to 



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 findt 



fluvia 



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Ch. XIX.] 



GROWTH OF THE MISSISSIPPI DELTA 



4G1 



sheets or layers, which the keels of vessels plough through, 



up a furrow of clear blue water, which forms a dark 



turning 



streak in the 



mi 



We may infer, 



summer 



sea is 



turbid and depositing mud, and in winter, when the 

 making reprisals on the delta, there is a large amount of 

 sediment dispersed far and wide and carried by currents to 

 the deeper and more distant parts of the gulf.' 



We learn from the recent survey of Humphreys an< n 



mouths 



or passes has been advancing for some time at the rate of 

 262 feet a year ; but this fact supplies us with no data for 

 estimating the rate of growth of the whole delta in past 

 times. On comparing a 

 years old, executed by Captain Gould * between the years 



map 



maps 



wards by the "United States surveyors (that by Talcott 

 1888, and that of Humphreys and Abbot in 1860), it app< 

 that the land at the South Pass 



in 



map 



having advanced, has receded about four miles within the 



limits 



last century. This return oi the sea to its old 

 less owing to this pass having ceased to be a great channel 

 of discharge, so that, instead of new additions being made 

 to the banks, there has been a loss even of some of the land 

 that had been gained. The denudation in such cases may 



feet, but it shows not only 



many 



estimate 



& 



the land by observations made during short periods, but how 

 extensively the coarse materials first thrown down on the 

 bars may subsequently be removed and spread out in thin 



strata over large spaces 



Even if we compare the two 



American surveys already alluded to, of 1838 and 1860, we 

 find that in this interval of twenty-two years a bank of new 

 land in the Pass a l'Outre, measuring two miles east and 

 west by half a mile north and south, had been lost or 

 away by the waves. 



cut 



may 



i 



* Capt. Richards, of the Hydrographical Office, had the kindness to show me the 



original of this map. 



