266 E. W. Hilgard—Geology of the Southwest. 
unqualified statements, that the drift “must date from the 
eriod of depression,” and that ‘‘ during a long period after the 
deposition of the drift the land stood at about its present level, 
” » If, -as'Peot 
mM 
form deposits with the wavy stratification of river alluvium, an 
alone produce such structure; and, if so, the Gulf shore must 
have been elevated to the extent of at least 450 feet above its 
present level, at the time the Calcasieu drift was deposited.t 
Moreover, the Calcasieu profilest show most convincingly the 
existence of ridges of denudation at the drift surface, as well as 
beneath it; and, similarly, subterranean ridges of drift mate- 
rial are frequently struck in wells on the Mississippi coast-t 
The drift materials are, equally, the last thing so far found 
beneath the Port Hudson clays in the Mississippi bottom ;—to 
what extent they have filled up that ancient trough, future 
borings must determine. 
I cannot, therefore, see on what grounds Prof. Hopkins as- 
sumes that the erosion of the drift surface took place while the 
land stood “ nearly” at its present level. If, Pe) expect, drift 
vel should be found underlying the strata of the New Or 
eans well, the minimum elevation of the Gulf coast, during 
and even after the Drift period, would be increased by several 
hundred feet. And I cannot refrain from once more calling 
attention to the obvious difference between the chemical status 
of the stratified drift of the South, and that of Illinois and In- 
iana. In the latter, lignitized trees and layers of muck are 
abundant, indicating submersion at a comparatively recent 
riod; while the “orange sand” of the Southwest, as hereto- 
fore repeatedly stated by me, as a rule contains nothing that 
eapable of further oxidation or solution by atmospheric ar 
cl unless it be silex. Such complete peroxidation a? 
lixiviation, the effects of which have largely extended into 
erlying formations, || unquestionably indicate a lo sub- 
aérial exposure, from which the Northwestern strati 
was in a great measure exempt. 
* This Journal, November, 1869, p. 335. Ibid, p. 344. 
$ Misa, Report, 1860, pp. 28 and 29. P ition Rep. 1860, p. 23- 
