85 



found applicable in a general way to the rocks of the Blue Ridge 

 and the intervening country. Beds of dark green rock containing 

 hornblende, are occasionally presented. Slates, schists, sandstones 

 and coarse conglomerates, sometimes but little changed, at others 

 modified in various degrees, succeed each other as we travel west. 

 From the South-west mountain, and even in the Blue Ridge, the 

 beds of rock exhibit the same features and the same general dip to 

 the east. In the Ragged mountain the rock usually occurring is a 

 coarse conglomerate or sandstone containing mica, and more or less 

 modified, so as to exhibit a structure partly crystalline. In a direc- 

 tion north-west from Charlottesville, a conglomerate containing 

 large pebbles of angular quartz occurs, and In the same vicinity 

 fine-grained yellowish sandstone. 



Most of these rocks contain a large proportion of felspar, so as 

 in some cases when disintegrated, to have many of the characters 

 of a kaolin. A bed of this species exposed near the University, has 

 been found by Professor Emmet to furnish a material susceptible 

 of various useful applications. When baked at a very high tempera- 

 ture, this rock may be made into hones of a very fine and sharp 

 texture. It admits of being readily carved or turned into crucibles 

 and other useful implements, for which it is well fitted, by its power 

 of withstanding heat; and for the same reason it forms a very 

 valuable fire brick. 



With the view of illustrating the structure of the Blue Ridge, 

 the following descriptive list is presented of the rocks which occur 

 at Turk's gap, beginning at the western, and proceeding to the 

 eastern base of the mountain. A series of beds in the main analo- 

 gous to those about to be described, may be observed at Rockfish 

 and Brown's gap, and other points which have been examined in 

 the course of the reconnoisance. 



In the profile all these rocks are exhibited dipping steeply to the 

 east, which is their position as observed at Turk's gap. But at the 

 Balcony falls, where the exposure of rock is extremely grand and 

 interesting, the beds on the western flank of the ridge are seen dip- 

 ping west ; east of this they are seen rolling and arching in a manner 

 to indicate violent disturbing action, and at length they assume the 

 ordinary eastern dip. At this place the sandstones of the western 

 base form beds of great thickness. They are for the most part 

 grayish, but some layers of a dark brown colour may be seen among 

 them. 



