Davis.J 
420 
[April 6, 
the fundamental assumption made in my earlier essay is weak- 
ened, it still appears to me reasonable to regard the existing 
rivers as the product of adjustment of stream to structure. I 
would not regard this conclusion in the light of a demonstration, 
but rather as a conclusion that gives reasonable explanation to 
various striking peculiarities exhibited by the rivers. The most 
manifest exception to this explanation is in the case of the Sus- 
quehanna, a short distance above Harrisburg, where it crosses 
two pairs of synclinal ridges, formed by the hard Carboniferous 
sandstone. This peculiarity in its course was regarded in my 
essay as a departure from an adjusted location on adjacent softer 
beds, produced by superimposition after the ridges had been 
baselevelled, and thinly covered with flood-plain or estuarine 
deposits, late in Cretaceous time : and certain special features of 
some of the Susquehanna tributaries were instanced in further 
support of this rather far-fetched hypothesis. In the light of Mr. 
Foerste’s paper, however, it may be now better to regard the 
Susquehanna above Harrisburg as a long surviving antecedent 
stream, while only the smaller rivers maybe properly regarded 
as adjusted in their courses. The further discussion of this special 
division of the problem will involve a more carelul examination 
of the Susquehanna branches to discover if they surely indicate 
superimposition through Cretaceous flood-plaining as I have 
already supposed, and also an examination of other similar 
rivers, such as the Delaware and the Potomac, to see if they and 
their branches also show the same peculiarities. This examina- 
tion I hope to undertake in the not distant future. Mention may 
be made in this connection of the results obtained by my co- 
worker, Mr. R. DeC. Ward, from a study of some small branches 
of the Delaware above Trenton, which appear to confirm the 
belief that flood-plained streams deflect their tributaries mouth- 
wards, as first announced I believe by Lombardini ; and that 
streams thus affected may retain their deflection even after eleva- 
tion, by which they are allowed to cut down through the flood - 
plain cover and thus superimpose themselves on the buried 
structures beneath. Although of small size, these streams serve 
to illustrate the process suspected in the somewhat larger tribu- 
taries of the Susquehanna, but the flood-plaining examined by 
Mr. Ward was of Tertiary date ; not Cretaceous, as supposed by 
me in the case of the Susquehanna. 
