472 H. D. Campbell—The Potsdam Group, Virginia. 
Blue Ridge and proceeding northwestward up the river we 
cross the following series of beds: 
material more or less water-worn. This bed is immediately 
followéd by several beds of slates and conglomerate sandstones 
which have evidently been much altered by heat from the sub- 
jacent igneous rocks. The aggregate thickness of these beds 
is above 120 feet. 
No. 2 is a heavy mass of sandstone about 360 feet thick. 
It consists of two varieties. The lower bed is a hard gray 
quartzite and is the material of the Baleony Rock. The upper 
bed is of a grayish and purplish color and finely conglomeritic 
in texture, 
No. 3 consists of dark colored slates with interstratified beds 
of specular iron ore ot low grade, having pebbles of quartz 
disseminated through them. The thickness of these slates 1s 
about 500 feet. 
No. 4is a hard bluish sandstone 150 feet thick, which has 
been locally displaced near the river, forming several waves 
that are conspicuous from the railroad. This feature is not 
represented on the section. 
o. 5 is a heavy bed of bluish and greenish slates about 
700 feet in thickness. They have been considerably warped 
and contorted. : 
No. 6 consists mostly of a brownish gray sandstone with 
very regularly jointed structure—90 feet thick. 
is made up of numerous thin beds of slate which pro- 
duce a variety of shades of color from nearly white and yellow 
to dark brown. ‘The coloring is produced by iron ore which 
encrusts many of the thin beds. The thickness of these slates 
is 120 feet. 
classed as Archean by Professors Wm. B. Rogers, J. L. Camp- 
bell and others, and have been spoken of as lying unconform- 
ably beneath the Potsdam sandstones and slates of the wester? 
