Davis and Wood.] 
420 
[Nov. 20, 
try. For example, the low pass from Jamesburg northwestward 
to Pigeon swamp, and from Monmouth Junction northwest by the 
railroad to the gap in Rocky Hill. It may be supposed that the 
Manalapan once flowed along these depressions, and that it was 
captured at Jamesburg by South river and in Pigeon swamp by 
Lawrence brook ; but much more work on the ground is needed 
before such suppositions need be accepted. No other place in the 
state offers so good an opportunity for investigations of this kind. 
The example of river piracy recently described by the senior au- 
thor in eastern Pennsylvania 1 belongs with these cases in the Mill- 
stone cycle. 
38. Marine erosion of the Central Plain in the Millstone cycle. 
The altitude given to the Cretaceous portion of the Central plain 
by the uplift that closed the Somerville cycle has been described 
as a gentle ascent southeastward from the fall-line : but the ascent 
ceases about the headwaters of the Millstone and Manalapan, and 
the surface continues with fairly uniform height for some distance 
further. Here the streams flow eastward ; they have trenched the 
plain rather strongly and at places it is much broken up ; but from 
the occurrence of sands and gravels in the broad valle} r s and from 
the appearance of steeper slopes on the seaward side of some of* 
the hills, we have supposed that the ocean has had a share in the 
opening of this country, in some portion of what is here called Mill- 
stone time, when the land stood lower than at present ; but how 
far this is the case cannot now be determined. It is interesting 
to notice in this connection that here for the first time do we find 
the shore waves responsible for determining an element in the to- 
pography of the state. 2 The Central plain appears to be purely 
a subaerial product as far eastward as it has been traced. The 
Triassic portion of the Schooley peneplain has been for good rea- 
sons regarded as of subaerial origin, although later buried under 
marine deposits. The Highland portion of the same peneplain and 
its extension far and wide into Pennsylvania fail of evenness by 
just such amounts as a plain of nearly ultimate land erosion should ; 
and the intermediate strip, where the shore line oscillated during 
'Cretaceous deposition, has not yet been identified as bearing marks 
•of littoral erosion. We therefore suppose that except during the 
Cretaceous transgression and the much smaller invasion of the sea 
river pirate. Science, xm, 1889, 108. 
2 McGee’s Columbia shore line, already referred to, is an exception to this statement, 
