10 
GEOLOGY OF NORTH CAROLINA. 
question was also frequently asked which presented a difficulty not ob- 
viously connected with the former, viz : why the marl beds, (Miocene 
shell beds), are found only on the south side of these large rivers. This 
observation was also very soon verified as to its general application. Pur- 
suing the subject, it was soon noticed that, as a consequence of this topo- 
graphical structure, the great roads as well as the towns and residences 
on these streams are located very generally on the same side, as may be 
seen by a glance at the map of the State. Another curious point may 
also be noted here . each of these rivers, between the point where it enters 
the champaign and its mouth, makes a gradual sweep towards the south, 
(some of them more than one); so that they consist of one or' more 
curves, whose convexity is turned southward, presenting the appearance 
on the map of a succession of catenaries. A cross section of these inter- 
fluvial zones will present about the following appearance : 
Ideal section across the Roanoke, Tar, Reuse and Cape Fear Rivers; 
d, Cretaceous; c, Eocene; b, Miocene; a, Quaternary. 
In seeking an explanation of this peculiar topography, the theory of a 
gradual subsidence towards the south was first considered. The objec- 
tions to it, however, were obvious and insuperable. Finding the same 
observation to bold for the corresponding region of South Carolina, I 
consulted the Geological Report of Prof. Tuomey. He had. noted the 
facts and their persistence through more than one State, but had rested 
in the theory of an unequal subsidence. The sufficient objection to this 
explanation is that there is no evidence of such a subsidence, but much 
evidence that it could not have taken place without producing a very ob- 
servable difference in the present horizon of the formations affected. 
And furthermore, the phenomenon is not confined to the superficial strata 
of the Quaternary or Tertiary formations. If the covering of these were 
removed, a section of the Cretaceous would present the same appearance. 
The cause, therefore, whatever it be, has acted over a very large territory, 
through a very long period. That cause is doubtless the rotation of the 
earth, co-acting with the force ot the river currents. Without stopping 
to refer to familiar instances of the sensible operation of this cosmical 
force in modifying the motions of projectiles, it is sufficient to refer to 
the well-known law of motions, developed by Prof. W. Ferrel in the 
Mathematical Monthly, vol. i. p. 307, according to which, “In whatever 
direction a body moves on the surface of the earth, there is a force arising 
