AND THE SALT DEPOSIT ON PETITE ANSE ISLAND. 



21 



Divers kinds of mineral springs seem to exist tliero. The area of the island is only 

 about three hundred and fifty acres, maximum elevation one hundred and twenty 

 feet; like the rest, it is surrounded by sea-marsh. 



Dupuy, Miller's or Orange Island, possesses about the same area as Petite Anse, 

 its maximum elevation above Gulf level being eighty-five feet. Thomassy describes, 

 as situated on the summit of the island, a " crater lake," exhibiting on its sides an 

 upper stratum of fine gray sand, and a lower one of rather angular quartz pebbles. 

 Mr. Dudley Avery, who described the island to me, could not locate this central 

 lake, but states that blufi" banks exhibit precisely the same materials as the interior 

 of Petite Anse. On the shore of Lake Peigneur, which borders the island on the 

 northwest, there is at one point an appearance as of a ledge of grcenisli, not very 

 solid sandstone, two feet below water level; it is coarser than the surrounding 

 sand strata. This would seem to indicate the presence of the coarse conglomeratic, 

 semi-indurate sandstones so commonly overlying the pebble-bed of the Stratified 

 Drift. 



THE ATTAKAPAS PRAIRIES. 



As already stated, the blue clay stratum underlies also the Attakapas prairies, 

 south of Bayou Teche. In cuts made in the prairie northward of Petite Anse, the 

 succession of strata, according to Mr. D. Avery, is as follows : — 



The structure of some of the level lands of Petite Anse is quite similar, 

 although the black prairie soil is now wanting, while the calcareous gravel is very 

 prominent. The same is the case in the prairie off Cute Blanche, where the thick- 

 ness of the concretionary stratum often exceeds a foot. The average elevation of 

 the Iberia prairie above tide-water is six to eight feet; which would place tlie top 

 of the blue clay stratum somewhat above Gulf level. But no stumps have been 

 found in the shallow prairie cuts, so that it is quite likely that the stump stratum 

 exhibited at Cute Blanche has not been reached in them. 



THE PORT HUDSON GROUP. 



The data above recorded, as will be perceived, were insufficient by themselves to 

 serve for the determination of the age of the rock-salt deposit. At the same time, 



