THE CORDILLERAN SECTION 731 



EXPLORATION OF THE FAMWEL CAVE 

 BY E. L. FURLONG* 



Published in the American Journal of Science, xxii, 235-247 (1906). 



EXCEPTIONAL NATURE AND GENESIS OF THE MISSISSIPPI DELTA 

 BY E. W. HILGARD 



[Abstract] 



This paper discusses the wholly exceptional materials and form of the lower 

 delta of the Mississippi river, as observed by the writer in 1807 and 1809, and 

 described and discussed in the American Journal of Science in 1871. Follow- 

 ing out the suggestions of Lyell and the disputed statement of Humphreys and 

 Abbott that the alluvial deposits of the great river are only of slight depth, 

 the writer investigated the extreme mouths of the passes, the "neck," and the 

 similar minor, birdfoot-like arms projecting beyond. It became apparent that 

 the silty river deposit on these narrow dikes or banks is only superficial, and 

 that their resistance to erosion during overflows is due to their being mainly 

 composed of tough, inerodable "mudlump clay." That these mudlumps, 

 observed and described by Lyell, are upheavals of the river bottom, and are 

 formed of such clay as is deposited outside of the bar, where the turbid water 

 of the river meets and is clarified by the saline sea water ; also, that the mud- 

 lump upheavals occur in the main outlets or passes of the river, as a direct 

 result of their being the main outlets. No mudlumps then existed in the South 

 pass, but now that it has been artificially made the main channel, mudlump 

 upheaval has taken and is taking place. Mudlump formation is thus the 

 normal mode of progression of the delta of the main Mississippi. 



No such phenomena are known to occur in any other river of the world; 

 hence no other river has such birdfoot mouths. The Mississippi delta should 

 not, therefore, be longer presented as the type of a normal delta, as is done 

 by Russell in his "Rivers of North America." 



The Section then adjourned for luncheon. 



At 2 p m the session was resumed and the following papers were read : 



INTERREGIONAL ZONES IN THE TRIASSIC OF WESTERN NORTH AMERICA 



BY J. P. SMITH * 



A NEW AMPHIBOLE 

 BY W. O. CALRKf 



NOTES ON PALEOZOIC CHERTS FROM MISSOURI 

 BY E. B. LANEY$ 



* Introduced by John C. Merriam. 



t Introduced by A. S. Eakle. 



t Introduced by Andrew C. Lawson. 



