95 
JOURNAL OF THE 
In portions of the coastal plain region, however, where 
the streams are cutting their way down across the hori- 
zontal and soft strata such as alternate beds of clay and 
sand, we have conditions somewhat similar to those de- 
Fic. 1.—Interbedded sands and clays favoring the 
development of rapids in river channels. 
P and P’—Finely laminated ard in places cross- 
bedded, black laminated clay below, and bedded but 
cross-laminated clayey arkose above, the strata of 
both clay and arkose being separated by layers of 
sand varying in thickness from a small part of an 
inch to several feet, The strata marked P’ above rr 
represent the same strata as P’ below the vr. s= 
Sand hills back from the stream border. /f—River 
terraces of recent loams, gravel at their base. 7r— 
Surface of the stream showing that asit washes away 
the laminated arkose and clay, irregular rapids are 
produced inthe stream, owing to the more rapid re- 
moval of the interbedded sand. 
scribed above except that in these cases 
the strata, instead of being alternate lay- 
ers of hard and soft rocks, are of altogeth- 
er unconsolidated materials which have 
not yet turned to stone. Such a condition 
of things may be illustrated by fig, 1, 
which represents somewhat the conditions 
existing on Rockfish creek in Cumberland 
county. 
In the lower portion of its course the 
waters of this creek have cut their 
way through the overlying sands and 
loams and are now cutting through the lower interbed- 
ded sands, clays and arkose, and the still lower more 
fineiy laminated sands and greenish-black clays. Near 
the mouth of Rockfish these materials in its bed have 
been worn away to the level of the Cape Fear river 
