38 Ei. W. Hilgard on the Tertiary formations 
So far, I have been unable to observe the marine Tertiary in 
juxtaposition with the Grand Gulf group on the Chickasawhay, 
and cannot positively assert that the former dips under the lat- 
ter atall. In Hinds, Rankin and Smith counties, their relative 
age is clearly exhibited, but it is possible that they do not over- 
lap very far, so that, were a portion of the superior furmation 
removed by denudatiou, the edge of the marine basin might be 
laid bare. Yet from the fact that at the very locality mentioned, 
the Vicksburg strata proper possess approximately the same ag- 
gregate thickness as elsewhere observed, we should not conclude 
that the stratum is about torun out, Nor isit easy to reconcile 
such a supposition with the grand scale on which these marine 
strata are developed in the direction of their strike, through the 
states of Alabama, Mississippi and Arkansas, and their relations 
to the Great Lignite. It would seem more natural to suppose 
that they form part of the deposits of a tertiary Gulf of Mexico, 
and now (either themselves or their deep sea equivalents) under- 
lie that gulf. Under this point of view, they might possibly be 
expected to reappear in Yucatan, along the foot of the Mexican 
plateau, in Texas, and forming a tongne, as it were, in the di- 
rection of the long cretaceous Mediterranean, and tertiary fresh- 
water sea which is marked by the Great Lignite of the upper 
issouri, 
In view of the slight dip of the Mississippi Tertiary, the anom- 
alies mentioned may find their explanation in undulations of the 
sea-bottom upon which these strata were deposited. A dip of ten 
deposition of the Jackson group, a northward slope to that ex- 
tent existed between Jackson and Canton, a subsequent general 
upheaval to the northward would render that slope a horizontal 
plain, while the strata heretofore horizontal would acquire a 
southward dip to the same extent. Similarly, if between Baker’s 
bluff and the Salt Works on the Tombigby, or between Dr. 
Miller’s and Red Bluff on the Chickasawhay, the sea bottom had 
a slight trough-shaped undulation (such as the ocean beds of our 
time frequently exhibit), the existing state of things would re- 
sult. Artesian borings lower down on the Tombigby river may 
hereafter inform us whether or not the white lirnestone underlies 
there, as by analogy with the Pearl river beds it might be ex- 
ected. 
: While, however, the general features and position of the Ter- 
tiary as well as of the Cretaceous strata of Alabama correspond 
closely with those observed in Mississippi, it seems, contrary to 
what one would expect, that the absolute amount of southward 
dip is somewhat less in the former state. No numerical data re- 
