1889.] 
411 
[Davis and Wood. 
but also a number of smaller streams which join it. The reasons 
given for this conclusion are that the location of the streams is not 
accordant with the initial structural surface of the range, for a num- 
ber of the branches of the river join it by monoclinal instead of 
sjmclinal valleys. But inasmuch as the region is one of enormous 
denudation, it does not seem unlikely that such monoclinal side 
valleys may be adjusted courses of consequent or superimposed 
streams, instead of persistent courses of antecedent streams ; for the 
process of adjustment by which hard courses are deserted for easier 
ones was not then considered. But this indoor correction of an 
outdoor conclusion is suggested only in a tentative way. 
31. The Kittatinny Valley. While the Central plain was devel- 
oped on the soft Triassic and Cretaceous beds, and the valleys of 
the Highlands were opened by their revived streams, the broad area 
of limestones and slates between the Highlands and the heavy out- 
crop of Medina sandstone near the northwestern line of the state 
was denuded into a broad lowland known as Kittatinny valley : all 
this being the work of the Somerville cycle. If the observer climb 
to the commanding summit of Jenny Jump mountain, one of the 
outlying masses on the northwest side of the Highlands, near the 
Delaware, he may see a great length of the Kittatinny valley low- 
land in New Jersey and Pennsjd vania, bounded on the west by 
Kittatinny mountain. The slates, that are associated with the 
limestones on the' northwestern side of the valley, are more resist- 
ant and form hills not yet reduced to the Somerville baselevel ; they 
are thus homologues of the hills formed on the harder Cretaceous 
beds on the southeastern part of the Central plain. In the same 
wa} 7 , the even crest of Kittatinny mountain corresponds with the 
even crests of the Watchung ridges, still preserving the general ele- 
vation of the Schooley peneplain. The extension of this peneplain 
into Pennsylvania and its relation to the development of valleys in 
that state have been elsewhere discussed by the senior author. 1 
The Millstone Deformation of the Central Plain. 
32. Present attitude of Central Plain. The Central plain has been 
unevenly lifted from the position that it held during its develop- 
ment, for it is not now so low or so level as it was then. Its pres- 
ent altitude is naturally the result of the summation of all the small 
‘The rivers and valleys of Pennsylvania. Nat. Geogr. Mag., I, 183-253. 
