474 [Mnrchr,, 
OIUGIN OF TUK LOWKK MISSISSII^PI. 
That a long period of subaerial denu<lation in pre-Cretaecons 
and Cretaceous time produced a ])eneplain thi-oughout the A]))>a- 
lachian region has become well known through the writings of 
McCtccI, Davis^, Willis^ and Hayes and Campbell*, but that 
the same general surface of denudation a]>pears west of the 
Mississippi is not well known, nor is the bearing of this fact u])on 
the lustoi'v of the lower Mississippi recognized. It is too 
conunonly assumed, even in recent articles, that the jMississij)pi 
has had its present course since Palaeozoic times. Westgate^ has 
indicated that such was probably not the case, and the writer 
wishes to ])resont the conditions bearing upon the history of this 
river more in detail, now having the additional information 
presented by Hayes and Campbell since Westgate's article was 
written. 
When profile sections are given illustrating the })osition of the 
Cretaceous peneplain of the Atlantic slope the surface of the 
plain is extended indefinitely beneath the cover of Cretaceous 
and later sediments ; and had Hayes and Campbell presented a 
section extending westward from the southern Appalachians the 
same indefinite extension below the sediments of the Mississippi 
eml)ayment would doubtless have been represented. 
' Three formations of tlio niiildlo Atlantic slope. W. J. M(^(Jee. Anicr. journ. sci., 
1888. 
2The rivers and valleys of Pennsylvania, W. M. Davis. Nat. p;eop,-. map,-,, v. 1, 
p. 183-253, 1889. 
The geographie development of northern New Jersey. \V. M. Davis and .). W, 
Wood, Jr. Proc. Host. soc. nat. hist., v. 24, p. 3G5-423, 18S9. 
The rivers of northern New .Jersey. W. M. Davis. Nat. geog. mag., v. 2, ]>, «1-110, 
1890. 
The geologic dates of origin of certain toiiograjihic forms on the Atlantic slope of 
the United States. W. M. Davis. Hnll. geol. soc. Amer., v. 2, \t. ."^.'W.Wl, 1890. 
■■'Uoiind abont Ashcville, Pailey Willis. Nat. geog. mag., v. 1, p. 291-;'.0(). 
" Geomorphology of the sonthern Apjialacliians. (". Willard Hayes and Marins K. 
Campbell. Nat. geog. mag., v. G, p. (l.'!-12(!. 
•'■'The geograpliie development of tlie eastern part of the Mississijipi drainage 
system, Lewis (i. Westgate. Amer. geol.. v. 11, Ai)ril. ]S9:!. 
