120 ANNUAL INCREASE! OF DELTA. [CHAP. XXIX. 



would make extensive inroads whenever the main channel of 

 discharge is altered and there is a local relaxation of the river s 

 power. Every year, as soon as the flood season is over, the tide 

 enters far up each channel, scouring out mud and sand, and 

 sweeping away many a bar, formed during the period of inunda 

 tion. Bringier, an experienced surveyor of New Orleans, told 

 me, that on revisiting the mouths of the Mississippi after an 

 interval of forty years, he was surprised to observe how station 

 ary their leading features had remained. Mr. Dunbar, also an 

 engineer in great practice in Louisiana, assured me that on com 

 paring the soundings lately made by him with those laid down 

 in the French maps of Sieur Diron, published in 1740, he found 

 the changes to be quite inconsiderable. On questioning the 

 pilots on the subject, they stated that the changes from year to 

 year are great, but are no measure whatever of those worked out 

 in a long period, for there seems to be a tendency in the action 

 of the tides and river to restore the old soundings. 



Captain Grahame, also a government surveyor, on comparing 

 the northeast pass with the charts made a century before, found 

 it had not advanced more than a quarter of a mile, and that in 

 the same interval the principal variations at the pass a Loutre 

 had consisted in the filling up of some bayous. Even if we could 

 assume that the progress of the whole delta in twenty-five years 

 was as great as that assigned by Linton to one or two narrow 

 channels and banks, it would have taken several thousand years 

 for the river to advance from New Orleans to the Balize ; but 

 when we take into our account the whole breadth of the delta, or 

 that part of it which has advanced beyond the general coast-line 

 above 100 miles across, we must allow an enormous period of 

 time for its accumulation. 



The popular belief in New Orleans, that the progress of the 

 banks near the mouths of the river has been very rapid, arises 

 partly from the nature of the evidence given by witnesses in the 

 law courts, in cases of insurance. When a ship is lost, the usual 

 line of defense on the part of the pilots, whether for themselves 

 or their friends, is to show that new sand-bars are forming, and 

 shoals shifting their places so fast, that no blame attaches to any 



