OF THE UNITED STATES. 11 
A white, soft limestone, not harder than some coarse 
ehalks, which it much resembles: replete with fossils. — 
All these varieties are occasionally infiltrated by sili- 
ceous matter, and considerable masses of chert are occa- 
sionally observed in them: they also present some ap- 
pearances of the green grains so characteristic of the 
marls adjacent. 
GEOGRAPHICAL DISTRIBUTION, ORGANIC CHARACTERS &c. 
When my attention was first called to this subject, 
eight years ago, I could not trace the ferruginous sand 
beyond the peninsula of New Jersey, and a small part of 
Delaware: subsequently, however, it has been discovered 
in nearly all the southern states, and I now believe it to 
be one of the most extensive formations on this continent. 
From the observations of Professor Hitchcock I have no 
doubt that it forms the substratum of the islands of Nan- 
tucket and Martha’s Vineyard, on the coast of Massachu- 
setts. Long Island will doubtless prove a link in the same 
series. But this formation is first unequivocally recog- 
nized in New Jersey, whence it may be locally traced 
through Delaware, Maryland, Virginia, North and South 
Carolina, Georgia, Alabama, Mississippi, Tennessee, Lou- 
isiana, Arkansas and Missouri. 
These various deposits, though seemingly insulated, 
are doubtless continuous, or nearly so, forming an irregu- 
lar crescent nearly three thousand miles in extent; and 
what is very remarkable, there is not only a generic ac- 
cordance between the fossil shells scattered through this 
vast tract, but in by far the greater number of compari- 
