218 Geology, §c. of Tennessee, §c. 
ghany; and constitutes one” of the most prominent. features in 
the geology of the United States. Its height I cannot deter- 
mine with accuracy. Probably it would not average more than 
one thousand feet. “Its base may extend in diameter from one 
to two miles; and yet such is the influence it has on the cli- 
mate, that vegetation on the eastern, is usually two weeks ear- 
lier than on the western side ; and what is remarkable, is, that this 
difference obtains, on the former side at least, until you arrive 
within a few hundred yards of the summit. 1 crossed the 
mountain in two places, distant from each other one hundred 
miles, but observed nothing essentially different in their mine- 
ralogy. At one of them called the Rockfish-Gap, on the road 
from Charlotteville to Staunton, I spent a few hours, and brought 
away specimens of all the varieties of minerals which I could 
_ These have been submitted to your inspection. Among 
them, you will, I think, see greenstone, epidote, and slate more 
or less allied to the first. These are the most common rocks, 
and excepting the second, are usually stratified. The epidote 
is generally associated with quartz, and sometimes is imbedded 
in it. In some instances it has a porphyritic appearance, and 
is very beautiful. In others, it is coated with small filaments 
of a greenish asbestos. Other minerals were found, whose 
nature I could not so easily determine. I regret exceedingly, 
that I cannot furnish you with a more complete description of 
this interesting mountain. That itscharacter is peculiar, oF 
ferent from that of the country on either side of it, must be obvi- 
ous to the most superficial observer. Its principal rock does in- 
deed bear a resemblance to the trap or greenstone of Albe- 
marle county, and yet I think you will say it is not the same 
One fact of importance cannot be mistaken ; this mountain con- 
stitutes the great dividing line between the granite and lime- 
stone countries. For you no sooner reach its western base, 
than the greenstone and epidote disappear; and limestone, pe: 
vades the country for hundreds of miles in every direction. In 
all the distance from this mountain to New-Orleans, I did not 
find a single specimen of granite, or greenstone. This: may 
appear singular, since Mr. Maclure and Professor Cleaveland 
