E. W. Eilgard— Geology of the Delta., 



Art. jay.— On the Geology of the Delta, and the Mudlumps of 

 the Passes (f the Mississippi; by EuG. W. Hilgard. 



A glance at the map shows that in descending the Mississippi 

 from New Orleans, we find a narrow strip of land only | to 3 

 miles wide, dividing the river from the waters of the Gulf: from 

 the head of Oyster Bay opposite Pointe a la Hache (about half 

 way between the city and the head of the Passes), clown to 

 the mouths. Such, at least, is the case on the left bank ; on tl it- 

 right, the "neck" begins a few miles below Fort Jackson. 

 Down to the forts, the aspect of the " Coast" is generally pretty 

 much the same, where its original character has not been lost by 

 cultivation or encroachment of the river. Nearest the river, 

 and highest above water level, are the sandy "willow bat- 

 tures," where the willow, mingled with and occasionally re- 

 placed by the cottonwood, forms the predominant growth. Be- 

 yond lies a belt of woodland, timbered chiefly with hve-oak, 

 magnolia, and cottonwood, often deeply veiled with long-moss ; 

 this belt embraces the richest and most durable soils of the 

 ''Lower Coast," and is mostly occupied by magnificent planta- 

 tions of sugar cane and orange orchards. Beyond these, loom 

 in the distance the sombre-hued, moss -curtained denizens ot 

 the^ cypress swamp, their tops forming a level platform sharply 

 defined against the horizon. Between the swamp and the wa- 

 ter's edge, seaward, there usually intervenes a zone of reeds, 

 with here and there a stunted cypress, bay, or candleberry busli, 

 where the salt water has but slight access. 



Whde such is the general order of succession of these belts 

 of vegetation where they coexist, either or both of the two 

 middle ones may locally be absent. Such is always the case 

 where the "neck" is very narrow, as happens below the forts. 

 Thence to the mouths of the passes, the willow batture and the 

 reed mai-sh alone, with few exceptions, form the barrier be- 

 tween the river and the sea ; it is traversed by numerous smah 

 bayous, some of which are in great part the work of the duck- 

 hunters that supply the New Orleans market, and whose pur- 

 suit leads them to penetrate the marsli for the purpose of reach- 

 mg the favorite resorts of their game. These bayous increase 

 in frequency as we descend, and in approaching the mouths oj 

 the passes, the intervals between them become smaller, uutij 

 they gradually become sheets of water dividing islands ; and 

 Imally, just inside the bar, we have the latter resolved into nu- 

 merous individual "mudlumps," dotting the surface of the sea, 

 on both sides of the main channel. 



