Davis and Wood.] 
418 
[Nov. 20, 
of the Millstone river at the close of the Somerville cycle must 
have been very liable to reversal of slope if an active change of 
level then took place. There is no measure of the activity of such 
a change of level, save in its effects. The Millstone now flows in 
a direction that clearly indicates an active uplift and tilting at the 
close of the Somerville cycle, and hence the active uplift may be 
accepted. The highest elevation reached by the Central Plain 
and still retained by it is in its Cretaceous portion, in the neighbor- 
hood of Clarkesburg : here it is about two hundred feet above sea 
level. The change suffered by the plain still farther southeast will 
be briefly considered in a later paragraph. The question here be- 
fore us is whether such an uplift, perhaps coupled with slight actual 
depression toward Bound Brook, might not reverse the hypotheti- 
cal southeastward course that the Millstone river is supposed to 
have had before. If the Central plain had not been dislocated, the 
reversal of the river would not be so difficult to believe ; but when 
it is remembered that the river in its hypothetically reversed course 
had to cross the fall-line dislocation against the uplift, that is, from 
the thrown to the heaved side of the fault, one may still hesitate 
to accept an explanation so peculiar. Still, as far as can be seen, 
there is no other solution than this. The reversal probably oc- 
curred before the dislocation ; and the dislocation at this point 
appears to have been slow and of moderate amount, for otherwise 
the Millstone headwaters would have found exit along the thrown 
margin of the fault, either southwest to the Delaware at Trenton or 
northeast to the Raritan below New Brunswick. Indeed, if the 
dislocation continue in the future, one or the other lateral escape 
of the Millstone headwaters is highly probable. 
The case is interesting as an apparent example of a rare occur- 
rence in the history of rivers. Few cases of the kind have been 
described. 
36. Deflection of the Delaware along the Fall-line Displacement. 
The Delaware, like some other streams of great age that have been 
revived from the Schooley to the Somerville and from the Somer- 
ville to the Millstone cycle, follows an ancient course across the 
Kittatinny valley and the Highlands, 1 and a superimposed course 
inherited from the Cretaceous cover of the Triassic belt from about 
the edge of the Highlands to Trenton ; but here it turns abruptly 
to the southwest. McGee has found explanation of this singular 
i Cf. McGee, l. c., 135. 
