49 



bt'tween Lake roiitchiirtrain and Lake Boriiiie. This stream is evideinly 

 a former distributary of the main stream. The bays along the edge of 

 the delta of which Barataria. Timbalier Jind Terre Bonne are examples, 

 show liow tlie advancing d(4ta arms extend around areas of gulf and 

 hem them in. Notice particularly Bay :Marchand, at the mouth of Bayou 

 la Fourche. and the separation of Timbalier and Terre Bonne bays by the 

 long narrow delta of Bayou Terre Bonne. 



This inclosing process is aided by the formation of barrier beaches 

 from point to point by wave action. True delta area is further indicated 

 by the straighter course of the river below Baton Rouge. The river is 

 very meandering through the whole length of the alluvial valley on 

 account of the gentle sloiie of the river bed. but below Baton Rouge it 

 becomes increasingly straight, altliough in the distance of two hundred 

 forty miles the fall is but five feet, or one-fourth inch per mile. As 

 streams always acquire the meandering habit on gentle slopes, this ap- 

 parent contradiction of the law of streaui tiow furnishes an interesting 

 problem. I propose this explanation: Tlie river flowing into the gulf 

 produces a current some distance out from the shore along the sides of 

 which the sediment is deposited more rapidly than in the swifter central 

 line of liow. Finally the narrow mud banks appear above the surface 

 along the course laid out by the current in the still waters of the gulf. 

 The tendency to meander shown at the head of the delta indicates the 

 inclination of the stream to conform to law. The stream is forming 

 meanders. Below New Orleans an abrupt bend appears as an apparent 

 refutation of tlie explanation of the straight lower course. This bend 

 represents an accident in the direct forward movement of the delta. Ob- 

 serve the streams lieginning near the eastern curve of this bend and the 

 tract of land extending east and partially inclosing Lake Borgne and 

 Mississippi Sound on the south. These streams and this strip of land 

 indicate a former course of the river. A crevass across the narrow south 

 bank caused the abandonment of the part below and the abrupt turn of 

 the river. A crevass called "The Jump.'" twenty miles above the mouth 

 of the river, indicates iiow a repetition of the above accident may occur. 

 A submarine fan is approaching the surface outside of this gap. The 

 southeast trend of the river through the delta and of the main area of 

 the delta itself may be due to the eastward movement of the Gulf 

 Stream off shore Avhich deflected the incoming river current to the east. 



4— A. OK Science, '04. 



