496 S. V. Woodyjun. — American and British Smfaie-Geology. 
1000 feet. below the sea-level ; and as this must liave brougbt the 
sea very high up the valley, its recession was a long affair, and the 
nmd of the Bluff formation consequently represents the long period 
of this recession which its outspread accompanied, the portions at 
higher elevations being the oldest. He adds tliat this submergence 
brought the waters of the Gulf of Mexico up the valley of the 
Mississippi until the sea covered all the lower half of Ohio; and 
that it was during the maximum of this submergence, and during 
the acccumulation of the beds 3a, that the actiou of the shore- waves 
formed the Ivames and Eskers which occur on the watershed be- 
tween the two basins ; but, as I have before observed, if the sea had 
thus overflowed the water-parting, we are met with the difficulty 
that the waters of the lake-basin would have become salt, of which 
no evidence is offered. Neither does Prof. Newberry offer us any 
evidence of marine organisms to prove the occupation of the upper 
parts of the Mississippi valley by the sea. He describes certaiu 
clays with sands and gravels, which, occurring in Southern Ohio, 
belong to the deposits of the Mississippi basin ; and these, he says, 
overlie a forest growth, which seems to be a continuation of that 
which, lying within the St. Lawrence basin, occurs over the Erie 
clay, and appear to be identical in age with the beds 3a. The 
relation which these clays, etc., bear to the Bluff formation of the 
Mississippi, he does not point out with sufficient clearness to enable 
me to apprehend precisely his view about them, but so far as I can 
gather front his memoir (p. 37), he regards them as the equivalent 
of that formation. If, however, the depression about New Orleans 
was coeval with that to which the marine clays of the Lower St. 
Lawrence and of the Atlantic coast are due, the Bluff formation 
would seem to have begun before this. Looking at the subject in 
the whole light afforded by the examination of the Glacial features of 
the St. Lawrence basin, as described by Prof. Newberry, it seems to 
me that the Bluff formation of the Mississippi valley must represent 
both the Glacial and the post-Glacial periods, and have commenced 
as far back at least as the Erie clay. Indeed, if the Suggestion that 
the Karnes and Eskers of the water-parting between the two basins 
in Ohio originated from the subaerial dissolution of the ice of tbe 
first sheet, when it rested there before shrinlcing back into the St. 
La wrence basin, and forming a lake, be sound, the finer mud carried 
off by the water in forming such Eskers and Karnes must have 
found its way into the Mississippi valley, and contributed to the 
material of the earlier part of the Bluff formation, whatever sub- 
mergence the Mississippi valley underwent having been confined 
to its lower or Gulf extremity. 1 
1 In reference to this Suggestion it would he interesting to learn to what extent 
rock-fragments have heen lound in the Mississippi valley which can be identified 
with rocks in situ in the St. Lawrence area. Prof. Newberry speaks of large 
quautities of gravel and boulders having heen carried through the waste weirs, 
penetrating the water-parting, and deposited in lines leading towards the valley of 
the Ohio, so that I infer such rock-fragments of lake-basin origin do abound within 
the limits of the Mississippi valley, and up to the line of Northern drift limit shown 
in the map. 
(To be continued in our next Number.) 
