402 HE. W. Hilgard—Geological History of the Gulf of Mexico. 
flow, have clearly been formed by simple disintegration of these 
strata, altogether independently of the river alluvium. 
These results fully confirm, therefore, the statement made by 
Gen. Humphreys,* that the Mississippi does not, as a rule, flow 
(Gen. Wade Hampton’s plantation), where a tube well has fur- 
nished a copious flow of combustible gas undiminished for 
many months. aor 
The swamp clays form, however, only the lower portion 0 
the Port Hudson beds. igher up, 
Hudson Sect there lie yellow or whitish silts and “ hard- 
ans.” + 
: a side of the valley, as shown on the map. 
i __ * Rep. on the Mississi river, p.98, etal + Thi Jour., vol. i, 1871, p- 345. 
- $ See profile in this Jon Yor Pons, sEocy | 
