Mnrbiit.] 488 [March 6, 
Again, tlie lowland is not a perfectly Hat stretch like the flood- 
plain of a large stream, but is a sliglitly uneven one. Its surface 
is varied by small hills and ridges such as Cypress Ridge, Jones 
Ridge, Negro Hill, Augusta Ridge, Duvalls Bluff, and many 
others, giving a maximum variation of relief of nearly 100 feet. 
The attitude of the St. Francois and L'Anguille Rivers indi- 
cates that the lowland was not excavated by one large stream. 
They both maintain their courses across the ridge. If a large 
stream had excavated the lowland and had subsequently aban- 
done<l it, these streams could not have crossed the ridge. .Streams 
cannot plow their way through an unbroken upland from one 
lowland to another. They can act only as saws and must 
commence on top of the upland.i 
In order to get these streams across the ridge we should have 
to suppose that the Pleistocene deposits filled up all the pre- 
Pleistocene inequalities and that these streams on reemergence 
were superposed on the ridge rocks. 
A relation of master stream, inner lowland, and inland-facing 
escarpment, similar to that existing in the Mississippi embayment, 
exists in the coastal plain region in the northeastern part of its 
extent in the United States. The Hudson River is the master 
stream of the area, corresponding to the Mississippi River in the 
embayment. The inner lowland, corresponding to the lowland 
west of Crowley's Ridge, is the lowland belt extending from 
New York City southwestward by Trentoji, Philadelphia, and 
Baltimore. The Delaware and Susquehanna Rivers are here 
deflected along the lowlands as are the White and Ouachita in 
Arkansas. Eastward from New York City the lowland corre- 
sponding to that on the eastern side of the Mississippi embay- 
ment is submerged in Long Island Sound. The coastward 
upland in this case, corresponding to Crowley's Ridge and its 
homologues in the Mississippi embayment, are the Cretaceous 
uplands of Long Island, New Jersey, and eastern Maryland. 
The same features continue further southward also. 
The foregoing is the result of study pursued in the geo- 
graphical laboratory at Harvard University under the direction 
of Prof. W. M. Davis. Field study may cause some modifica- 
tion of the views herein ex])ressed. 
1 It is of (iourse possible for a sti-eara to sap its way through a narrow upland but 
there is no evidence in either case here that this has occurred. 
