224 Geology, $c. of Tennessee, &c. 
~ inclined. Like the Cumberland, it contains immense rocks of 
sandstone, but of a coarser grain, verging occasionally into 
pudding stone. I was told by a white man, a professed mill- 
wright, that among these sandstone rocks he knew of many 
which were suitable for millstones. At the missionary establish- 
ment, called “Brainerd,” eight miles east of the mountain, ! 
saw one of them which was used for this purpose to much ad- 
tage. Itis composed of fine and large grains of silicious stones, 
nearly white, and resembling pebbles of white quartz ; the tex- 
. ture is firm. 
Silicious Minerals, &c. 
_ Lwill now notice an important fact, applicable to the whole 
extent of limestone country, which has come under my observa- 
tion. It is its association with a description of minerals, all of 
which appear to be silicious. To describe them minutely, would 
require several pages. From the time I entered the limestone 
country. till | left it, this association was observed. The minerals 
included. in it, differ much in their external character. Theit 
size varies from that of rocks to the smallest fragments. Usual- 
ly they lie loose upon the earth, in angular forms, having the 
appearance of a stone that has been broken in pieces by the ham- 
mer. Sometimes they cover the sides of hills and mountains in 
such abundance as to prevent or impede vegetation. When 
disintegration is minute, they are serviceable rather than other 
wise; and the farmer talks of his ‘good black,” or “ white gravel 
land.” It renders this service, I presume, not by decomposition, 
but by preventing the soil and its. manure from being wash 
away. Indeed the different varieties of it are generally scatter 
ever the surface, in pieces so small, that for convenience sake, the 
whole may be denominated a silicious gravel. 
Sometimes the mineral is imbedded in limestone, in the form 
of nodules, thus indicating their original connexion with if. 
