AND T U I<: SALT D E P S I T O N P !■: T ITU A \ S E 1 S I, A N 1) . 25 



it frequently crops out on the surface, forniini( the '-hucksliot huid" at a level con- 

 siderably above high water.' 



The same state of things obtains in the Tensas bottom, opposite Rodney. A large 

 portion of the best lands of that region is almost a prairie soil, filled with calcareous 

 concretions, and totally unlike any alluvium now forming. I have also found out- 

 crops of this material in the banks of the bayous of that region. 



According to Hopkins, the Avoyelles prairie belongs chiefly if not wholly to the 

 same category ; being an outlier, as it were, of the Attakapas prairies. 



Ilinnphreys and Abbot give the following additional data regarding the occur- 

 rence of blue clay strata in the lower portion of Louisiana. At the head of baytni 

 Lafourche, and at Thibodeauxville; in the canal between Lockport and Lake Field; 

 at all of which points it occurs at about mean Gulf level. It forms the bottom of 

 Grand Lake, and in tlie same region has lately been foiurd in a well at the residence 

 of C'apt. Kerr, opposite Jeannerette's P.O. on the Teche ; here also at tide-level. 

 It also occurs on the line of the Opelousas railroad, both east and west of bayou 

 Lafourche, a few feet below Gulf level. 



AVhen it is considered how rare arc the opportunities for observing the strata 

 ruiderlying at a depth exceeding a few feet, in a level country where wells and 

 cellars are almost unknown, the fact that the blue clay stratum has been found in 

 almost every case when a greater depth was reached, must be taken as strong proof 

 that its prevalence is a genera! one; always excepting, of course, the old river 

 channels. It may be that in some cases, modern cypress swamps filled up by river 

 deposit have been struck. But there is no ground, either historical or natural, for 

 supposing that since the Terrace epoch of elevation, when the present Mississippi 

 valley was cut into the Loess deposits, the whole bottom or delta plain has ever 

 been one vast swamp. This could not have happened without a subsequent re- 

 depression, of which there is not the slightest proof; while, on the other hand, the 

 lithological and stratigraphical connection with the Port Hudson series is exeediugly 

 cogent. 



If, however, this ancient cypress swamp stratum in the Mississippi bottom be 

 really the representative of an era anterior to the Terrace epoch, similar vestiges 

 of the slow depression which could have produced it, must exist in the larger 

 tributary valleys. That this is the case in that of Eed Hiver, I have already stated. 

 My own observations have, it is true, been confined to the portion of tlie river lying 

 between Grand Bayou and Coushatta Chute Landing ; but I have the most direct 

 testimony that all the way below, and above as high as Shrevcport, the banks of 

 Red River exhibit precisely the same aspect. 



I give below two sections of the banks of Red River at a medium stage of water. 

 They represent fairly the general condition of things, profile No. 2 being, however, 

 by far predominant; i.e. the clay strata, whether red or blue, with strings of cal- 

 careous concretions on the stratification lines, occupy, as a rule, the bed of the river; 

 tlieir thickness being sometimes, as I am informed, twenty-five to thirty feet and 

 over. 



' Report on the Missi.«sippi River, p. 9S. 



4 May, 1872. 



