2 ON THE GEOLOGY OP IjOWEU LOUISIANA 



Meanwhile, in November, 1866, an investigation of the salt deposit was under- 

 taken by Dr. Chas. Gocssmann, under the auspices of the American Bureau of 

 Mines.^ Its object was chiefly, of course, to ascertain the probability of economical 

 success in working the mine ; the geological relations of the bed coming into con- 

 sideration mainly with a view to this object. Dr. Goessmann's able report is 

 exhaustive as regards the practical part of the subject. The notes, specimens, 

 maps, and hypsometrical observations, with which he kindly furnished me, were of 

 essential assistance. They led me to believe, at the time, that the predominant 

 surface formation of the island was the equivalent of the "Orange Sand," the 

 prevalent surface formation of the uplands of Mississippi, which I consider as con- 

 temporary, and substantially identical with the "Modifled Drift" of the North- 

 west.^ I thought that the chain of elevations or " islands," mentioned by Thomassy 

 and Dr. Goessmann, might be of a similar origin as those frequently observed in 

 level portions of the State of Mississippi,'' which are manifestly outliers of the main 

 body, that have resisted denudation by the greater firmness of their material. This 

 supposition, however, rested merely upon lithological resemblance, while later 

 fluviatile deposits might exhibit a very similar aspect. 



The solution of the problem involved, of necessity, a general examination of the 

 ancient and modern deposits as well as the delta formations of the Mississippi 

 Valley, and adjacent Gulf coast ; and this work had to be commenced from some 

 point where the formations were previously known and identified. In conformity 

 with this requirement, I proceeded from Vicksburg, the most southerly outcrop 

 of the fossiliferous marine tertiary, to the present mouths of the Mississippi, land- 

 ing at intermediate points where observations were needed. After this I went up 

 the coast to the islands, of which the examination formed tlie original object of 

 the expedition. 



The unxisually low stage of water, as well as the magnificent weather enjoyed in 

 these latitudes during the early part of the winter, gave me advantages, without 

 which the brief space of time at my command would not have sufficed to carry out 

 my plan of operations ; for the successful prosecution of which I am also largely 

 indebted to the courtesy and generous liberality, both of private individuals, and 

 transportation companies.* 



^ Report of the American Bureau of Mines on the Rock-salt Deposit of Petite Ansa; New York, 

 1867. 



» Amer. Journ. Science, May, 1866, p. 311; Ibid., Nov. 1866; Ibid., Dec. 1871. 



' Report on the Geology and Agriculture of Mississippi, 1860, p. 8. 



* I have to acknowledge favors in the way of free transportation, both for myself and my travelling 

 companion (Dr. E. Fontaine, Secretary of the New Orleans Academy of Sciences), on the part of 

 Mr. Moulton, of the Cromwell line of steamers; Capt. Ed. Yorke, of the Towboat Association; 

 Capt. Andrews, of the dredgeboat at the S. W. Pass; Capt. Bayley, Superintendent of the Opelonsas 

 Railroad, and Capt. Trinidad, of the Steamer Anna E., on the Bayou Teche. In my examination of 

 the Passes and Mudlumps of the lower delta, I have had the assistance of Capt. Day, with a boat's 

 crew, of the U. S. coast survey schooner Yarina, moored at tlie head of the Passes. For infur- 

 mation, hospitality, and other favors, I am indebted to Dr. Copes, President of the New Orleans 

 Academy of Sciences, and other members of that body; to Gen. Beauregard; to Capt. Tilford and 

 others, of the Pilot Association ; to Judge Avery, the proprietor of the salt mine, and his amiable 



