and the MucUumps of the Afissmippi 



usual sense, but in a great measure the result of 

 deposition ; while the surface slope of the Port Hudson deposits 

 is manifestly in a great degree due to denudation, and in part, 

 n(> doubt, to deposition on a sloping bottom. At Port Hudson 

 as well as elsewhere, where extensive profiles can be seen, the 

 tL'l)o.sits of that era exhibit the basin shape ; both on the large 

 and. sometimes, on the small scale. In this as well as in their 

 HtUological and paleontological features, thev greatly resemble 

 deposits now forming over large areas ; and where the two are 

 in juxtaposition, it is often difficult, sometimes impossible, to 

 draw the line between them, since qualitatively their process of 

 formation has been manifestly the same. Both above and 

 below Port Hudson, and down as far as Fort St Philip, the 

 apparently alluvial river banks frequently exhibit at low water 

 edge, solid blue clays, with cypress stumps and twigs imbedded 

 therein, scarcely distinguishable from some materials occurring 

 at Port Hudson, Cote Blanche, and other localities of the Port 

 Hxulson age ; and as neither can be expected to contain any but 

 living organisms, it is, thus far, from general considerations 

 alone, that we can hope to deduce their real age. It might 

 seem, at first sight, that the distinction is practically of little 

 moment; but when it is considered that the Port Hudson 

 deposits are separated in time from those of the present era, by 

 ''large portion of the " Champlain" period of depression, p/i/s 

 the entire " Terrace " period of elevation, it becomes obvious 

 that the distinction is one of no little theoretical, and some 

 practical, interest For while the Port Hudson strata yield to 

 the augur almost invariably a considerable rise of artesian 

 water, no such result can usually be looked for in either river 

 or delta deposits. 



I think that a retrospective view of the geological history of 

 the lower Mississippi Vallev and Gulf Coast, as developed by 

 niy observations in the States of Mississippi and Louisiana, will 

 serve to show the probability that by far the greater portion of 

 What now constitutes the alluvial plain of the lower Mississippi 

 IS covered by the river deposits to a comparatively insignificant 

 .<teptji only ; excepting where the ever shifting river channel 

 "self has caused an unusual depth by excavation and subse- 

 quent filling up. 



I have shown that toward the close of the Drift period, the 

 pace of the present Mississippi was occupied by what, but for 

 "\^*'ipendous proportions, might be termed a torrent of fresh 

 water, having, even as far south as the present coast line, a 

 velocity s^fficig^^ to transport pebbles of five to six ounces 

 ^eight, from localities not nearer than Tennessee and northern 

 Arkansas ; together with the smaller ones derived, doubtless, 



