216 L. C. Johnson — Grand- Gulf Formation of Gulf States. 



west, everything has been washed away and again covered, so 

 as to alter and hide the original bluff down to the compact 

 fucoidal sands, which a full stage of water would protect and 

 conceal. And at the other point mentioned where the 

 fossiliferous layers are first seen beneath double-bedded joint 

 clays, quite a bold spring branch comes in with like effect ; 

 for it has cut through all the layers down to low water and by 

 stealing out in preference the soft, sandy layers, has so let 

 down and distorted the lay of the clays, that it is difficult to 

 determine the clip. On occasion of the first visit the writer 

 supposed it to be the same as that of the calcareous beds. Upon 

 further observation, he is satisfied that it is less. That is : 

 putting the dip of the Vicksburg rocks at thirty feet to the 

 mile — and it cannot be less — the Grand Gulf is probably about 

 twenty feet and can scarcely be more. To settle this exactly 

 will require further and more careful observation. 



This layer of the Yicksburg formation, in which the great 

 oysters abound, may be followed up the river more than two 

 miles, and cannot be much less than forty feet in thickness. 

 Echinoderms and corals become more common in the lower 

 portions of it, and with them, among other things, are conspic- 

 uous the great tubes of Asjpergillum or some kindred 

 Tubicola — all forming a transition of Rotten limestone, before 

 passing to the hard bluffs of Orbitoides rocks, constituting so 

 much of the river bed for the next six miles. 



All the eastern bank of the river is made of a kind of 

 second-bottom, from one to three miles in width, having a few 

 low places through which the river runs at high water, and 

 many sandy knolls over which the water never rises. In some 

 of these branches, and in all the wells dug in this flat, the 

 Rotten marl, having shells of Ostrea Yicksburg ensis, is found 

 near the surface. Along the foot of the hills eastward there 

 are sand hills and benches, evidently remnants of an olden 

 terrace. 



The older terrace constitutes wholly the western bank of the 

 river and its towering bluffs. At Cochran's Ferry the bluff 

 cannot be less than one hundred feet high, and consists 

 entirely of soft sands, resembling " Orange Sand." Though 

 so near the terrace of compact clays at Brown's Bend, these 

 sands at Cochran's have not the faintest resemblance to the 

 Grand Gulf strata of the hills to the west and south. Evi- 

 dently there has been a great erosion, and refilling at this 

 point and for some miles farther north ; all which may be 

 gathered from the section herewith exhibited. 



These notes are offered, not with a view to controversy, or 

 to re-open a discussion : It can hardly be said, that there is a 

 serious doubt in the premises, but as a statement of facts, and 

 an attempted description of a locality in itself interesting, and 

 worthy of a visit. 



