The Mississippi Survey. — Hilgard. 307 
ing from Oxford to Yazoo City via the Pontotoc, "Flatwoods," 
Kosciusko and Jackson. 
He then descended into the Yazoo bottom and traversed it, 
zigzagging from the river to the bluff from near Vicksburg to 
its head near Memphis. In this laborious and insalubrious 
trip he studied carefully both the surface features of the 
great alluvial plain, and the geological features of the deposits 
that form its substrata. A summary report of this impor- 
tant exploration was given by him at the Indianapolis meet- 
ing of the A. A. A. S., and was published in the volume of 
Proceedings of 1871, p. 252. The outcome of these observa- 
tions is there summarily stated to have been that "the true river 
deposits, of any considerable thickness, are mostly confined to 
narrow strips of land lying on both sides of the Mississippi 
and of the bayous and creeks, and to ancient channels since fill- 
ed up ; while a large proportion of the superficial area of the 
bottom, including some of the most fertile lands, is derived 
from the clays of older formations into which these beds have 
been excavated." The equivalence of this older clay formation 
with that of the Port Hudson profile, already suggested by me, 
was thus fully verified. 
Returning to Oxford early in December, Dr. Smith carried 
on the chemical work until the end of May, 1871, when he took 
the field again in order to trace across the state the "Siliceous 
Claiborne" belt, referred to. His route lay from Leake county 
southeastward to the Alabama line, along the northern contact 
of the problematic "Red Hills" and yellow standstones with the 
lignitic formation ; then westward again in the more southerly 
portion of the belt, to the border of the Yazoo bottom (the 
"Mississippi bluff"). In this trip he traced the connection and 
established the equivalence of the ferruginous formation as a 
local feature, with the sandstones of Neshoba and Newton 
counties ; which connect unequivocally with the characteristic 
"burstones" of Lauderdale.* The beds of the Jackson group 
were then traced by him, down the edge of the bluff to 
Yazoo City and Mcksburg, forming the third complete section 
across the eocene observed in Mississippi. 
*The moro exteiultvl development of the ferruKinou.s feature iti northern 
Louisiana was afterwards observed and described by myself. Am. Jour. 
Sci., Nov., 1S(!!>. p. ."Ul : SiipplPiuciitarii ami pnal report of n i/rolot/icitl re- 
connoixancv of Louisitrxii, p. lili. Also Kep. on the cotton production and 
agricultural features of Louisiana, in Itvport of the 10th C'c>i.fi(.s ('. .v.. Vol. 
5, pp. 11-J. i:!L'. 
