222 Geology, §c. of Tennessee, §c. 
miles, to more than fifty. Its height is not perceptibly differ- 
ent from that of the Blue Ridge. It forms a circuit, in a shape 
somewhat resembling a half moon. Winding to the southwest, 
it keeps a course north of the Tennessee river, in some places 
nearly parallel with it; passes a few miles to the southeast of 
Huntsville in the Alabama Territory, and not long after termin- 
ates. At one part, over which I crossed, the mountain is eigh- 
teen miles wide. This is about 150 miles southwest of Knox- 
ville, a little north of the 35th degree of N. Lat. I had not 
ascended the mountain more than half way, before I found sand- 
stone begin to intermingle with limestone strata. As I drew 
near the summit, the limestone disappeared entirely, and sand- 
stone prevailed in abundance, with no other mineral associated 
until I reached the western descent, where I met bold precipi- 
ces of horizontal limestone, reaching from the base to the sum- 
mit. I examined several sandstone rocks while crossing the 
mountain, and found them usually imbedded in the earth, g peral- 
ly with flat surfaces, of a fine grain, and strong texture. The 
color is usuallya reddish brown, or grayish red. The specimen 
which you have received is a good example. I crossed this 
mountain in the vicinity of Huntsville, not less than one hun- 
dred miles southwest of the place above-mentioned, and found it 
not wider than mountains commonly are. Its height had also 
become less, and horizontal limestone in regular strata prevail- 
ed in every part. 
Although this mountain forms a part of the dividing line which 
has been mentioned, it does not do so exclusively : for the Rackoop 
mountain, which crosses the Tennessee river, at the place so 
well known by the name of “the Suck,” and the Look-Out 
mountain, which terminates abruptly about 6 miles to the left of 
" the Suck,” form an acute angle with the Cumberland, and are 
composed of horizontal strata of limestone. ‘Thus it would ap- 
pear that the line which divides the two kingdoms of this rock, 
runs nearly north and south, inclining perhaps a few poin's ‘ 
the east and west. 
