AND TOE SALT DEPOSIT ON PETITE ANSE ISLAND. 



FROM VICKSBURG TO PORT HUDSON. 



At Vicksburg. in consequence of extreme low water, I was enabled to examine 

 the portion of the noted profile at this place not usually exposed, viz., the whole of 

 the lignite bed, and fully four feet of the underlying materials. The latter consist 

 of bluish sandy clays, or clayey sands,^ not at all similar to the blue clay found in 

 the section exposed in the canal attempted to be cut across the neck of land below 

 the city during the war. It will be remembered that the tenacity of the clay in 

 question not only rendered the process of excavation exceedingly laborious, but 

 also prevented the anticipated washing out of a broad channel or "chute" during 

 high water. No such resistance would have been experienced from the materials 

 underlying the lignite bed at the foot of the bluff. The clay^ in the canal is doubt- 

 less of the same age and origin as that observed farther up, according to Humphreys 

 and Abbot,- in the beds and bottoms of the ^Mississippi, Sunflower and Yazoo llivers; 

 and wliose wide diffusion over the alluvial area of the Lower Mississippi I have 

 had abundant opportunity of observing. 



Having on a previous occasion^ minutely examined the bluff at Grand Gulf, to 

 which that at Rodney, according to late observations by Dr. Geo. Little (the pre- 

 sent State geologist of Mississippi), is substantially similar, I directed my attention 

 to the Natchez bluff, where marine shells have also been reported as occurring. 



The Natchez profile, essentially the same as that at Fort Adams,* is as follows: — 



family, as well as his son-in-law, E. Mcllhenny, Esq.; to Dr. Dungan, of Jcanncrcttos P.O., who 

 placed his time and conveyance at our disposal for several days, in visiting Weeks' Island and Cote 

 Blanche. Also to Judge Robertson, of New Orleans, the author of a valuable report to the State 

 Legislature, on the resources of Louisiana ; and to other gentlemen who manifested so much interest 

 in the objects of my expedition, as to make it a matter of surprise that a full geological survey of the 

 State has not sooner been set on foot 



' In the profile presented in my Report on the Geology of Mississippi, p. 141, I have given "white 

 limestone" as underlying the lignite, on the authority of Prof W. D. Moore. As the water was not 

 as low during his visit as at my late one, I presume that one of the numerous landslides misled Prof. 

 Moore, the rock having doubtless fallen from above. 



' Report on the Physics and Hydraulics of the Mississippi River, 18fil ; pp. 84 and 85. 



» Miss. Rep. ISfiO, p. 148. * Ibid., p. 150. 



