34 ON THE GEOLOGY OP LOWER LOUISIANA, ETC. 



change of character, as must characterize any deposit formed on a small scale, seems 

 a fit counterpart to the great gypsum bed of Calcasieu, with which the general dip 

 of the formation would naturally connect it. 



In a coimtry whose geological structure is less simple than that of the Gulf 

 States, such reasoning might seem trivial and of little weight. But there is in the 

 simplicity of the general features of conformation in the whole of the Gulf border, 

 an irrepressible cogency that can neither be ignored nor evaded. There are but 

 few reasonable possibilities in the explanation of any of its phenomena, albeit there 

 is no limit to fancies. 



The question of age has a most important bearing upon that of the extent of the 

 salt deposit. If of comparatively modem date, it must be accounted as more or 

 less the residt of local accident, and therefore of small extent. If of cretaceous 

 age, and therefore resulting from causes acting over great areas, its original extent 

 might have to be measured by hundreds of square miles; although its present, and 

 above all its available, mass would be seriously less, in consequence of its long ex- 

 posure to the action of water, from early eocene times to that of the Drift. The 

 borings show that, like all other formations that have been subject to the action of 

 the Drift currents, it is deeply denuded, forming "hills within hills." It is my 

 belief that on some points of the island of Petite Anse, it could be reached by level 

 adits; and, as woiked at the present time, I think there is much less danger of 

 "knocking the bottom out" by deepening the mine, than there is of "getting to 

 the jumping-oiF-place" by extending the galleries. So long as the purity of the 

 mass is not seriously impaired by admixture of gypsum, there is little likelihood 

 that the floor of the stratum is at hand. 



The borings thus far made with a vicv/ to determining, either the area of the 

 Petite Anse mass, or the existence of rock-salt on the neighboring islands, have 

 remained far within the limits beyond which its extraction would become too costly. 

 And although a mass of salt one hundred and forty-four acres in extent and seventy 

 feet thick may be considered a handsome specimen, yet industry is too deeply 

 interested in the cheapness and abundance of this fundamental article, not to render 

 its discovery at other points a matter of very great importance. And this import- 

 ance will be greatly enhanced if, as I venture to predict, the great sulphur bed of 

 Cidcasieu (the probable contemporary and congener of the rock-salt mass of Petite 

 Anse), shidl be found, from analogous causes, of a correlative magnitude. 



PUBLISHED BY THE SMITHSONIAN INSTITUTION, 



JUNE, 1872. 



