OF SOUTH CAROLINA. 133 
latter State, as high as the Miocene beds. ‘This is also the case at Martha’s Vineyard, in Massa- 
chusetts, where Prof. Hitchcock has determined the existence of the Tertiary formation. In North 
Carolina, although the Cretaceous strata resemble in color and external appearance the Eocene 
green sand beds of Virginia, yet that mineral is very rare as an ingredient of those strata—at least 
where I have examined them, at Wilmington, and other localities higher up the Cape Fear. 
In South Carolina I have not found a grain of green sand in the Cretaceous formation, and yet a 
bed of green sand, three or four feet in thickness, is found in the Eocene of the Santee River, and 
large grains, disseminated through some of the superincumbent calcareous beds. 
It seems, then, that the quantity of green sand in the Cretaceous beds of the Atlantic coast 
becomes less and less towards the South, until it disappears altogether from them, in South Carolina. 
The chemical composition of this mineral, it seems to me, leaves but little doubt as to its identity 
with those compounds known as clauconite, green earth, &e. 
The following table presents the composition of green sand, from different localities in the United 
States, and of the green earth of Europe. 
Marrna’s Vineyarp.* New Jersey.| Gerrmany.f Scorranp.§ 
Sigg ok 2. eae oO H00. cobs asso 48.4522. 2.682 AGW - 5 48:16 
Alumina _._..---. ele) Sa (33) eee tae Soe (ois 
Rrowx of lron. 22-20; 100 222 eee Pay he at ple de 19655222 -219'00 
(Potash. 253 436 6 eebi deus. 117-0) es Eh ea ee eee 6.56 
Magnesia_.--.-... ya See ae oe S Ree je eas 2.91 
Ines Aa eT O24 ees ee TAC ee 7) 
Water. ea SF 7000S 8:4 eee eee SOR P35) 
Quiamtids- se.a895 jo ccs ee eis al LtSsise. Se ———= 
99.920 99.47 100.7 98.50 
The green earth of Europe is found occupying cavities in trap rocks; and if our green sand, as 
there is every reason to suppose, be identical with it, we may safely refer its origin to the vast 
series of trap dykes found along the Atlantic slope, from New Jersey to the Coosa River, in 
Alabama. 
The debris of these rocks, washed down into the Cretaceous and Tertiary seas, would be quite 
sufficient to furnish the green sand of these formations—to say nothing of the probability of erup- 
tions of trap in the seas of those periods, 
The beds of green sand, of Virginia, present unequivocal evidence of their origin in the ruins of 
the older rocks, for near their upper verge they abound in fragments of limpid, smoky, and even 
rose quartz, sometimes rounded, but more frequently angular. 
The Cretaceous formation of South Carolina is a continuation of the beds so finely exposed on 
the Cape Fear River, in North Carolina; it is seen again on a creek about half-way between Wil- 
mington and Horry District. It dips beneath the sands of the coast, und is covered by Tertiary 
beds. In the District just named, however, this covering is so slight as to be removed by the 
waves, and cretaceous fossils are washed up on the beach. I found, at this place, which is a few 
miles south of the mouth of Little River, numerous valves of Exogyra costata ; and this is the 
*Dr. L. S. Dana. tRogers. :Berthier. §Thomson. 
34 
