EL. W. Hilgard—Geological History of the Gulf of Mexico. 399 
Safford in Middle and Eastern Tennessee, and by Tuomey and 
myself in Alabama. The same is true, apparently of the larger 
channels of Texas. But within the limits of the Mississippi 
embayment, it constitutes one huge delta-shaped mass, covering 
the entire Tertiary, and a large portion of the Cretaceous area, 
to a depth varying from a few feet to over two hundred; on an 
average, perhaps, between sixty and one hundred feet. Its pre- 
dominant material is orange or reddish, rounded sand, mostly 
ferruginous, of various degrees of induration, with subordinate 
beds of clay, and enormous gravel-streams, evidently denoting 
ancient channels.* Its beds disappear beneath those of the 
ort Hudson age about concurrently with those of the Grand 
Gulf era; and consequently, it cannot well be independently 
represented on the map. 
ead of the w is elevation was succeeded, during the 
“Champlain” epoch, by a slow depression to at least twice that 
amount ; and finally, the Terrace epoch, a re-elevation 
be changed upward, accordingly. The same, 
mm a reverse direction, would be true if it could be assumed 
m 
that the occurrence of the glacial epoch sensibly affected the 
general level of the ocean. 
bles of many pounds weight ; while between these, the deposi- 
tion of the finer materials took place in more quiet waters. 
That these events were not of a local character; that on the 
contrary, the phenomena observed in the Southern States are 
but the necessary consequence and complement of the Drift 
Phenomena at the North, hardly requires discussion ; but it 1s 
time that these facts were more gi y understood and taken 
ito account by American geologists, and that the Ohio should 
* Miss. Rep., 1860, this Jour., May, 1866, and other papers above referred to. 
+ This Jour., Nov., 1869, p. 335. 
