364 Campbell — Rogers's Geology of the Virginias. 



exposures are found near Goochland C. H. of beds of gneiss 

 and slates; and at Columbia quarries of gneissoid granites are 

 worked, and several gold mines are not far north of the same 

 point. Bremo Bluff, a few miles farther up the river, presents 

 some good points in the great gold-bearing slate belt. This is 

 the best point of departure for visiting Buckingham, one of 

 the most interesting mineral counties in the State. A few 

 miles west of Scottsville in Albemarle county, the line enters 

 the limestone belt described above, and changes its course 

 toward the southwest. The river has cut a serpentine channel 

 of considerable depth in the general direction of the strike of 

 this belt and exposed the limestones and their associated rocks 

 to view at numerous points for a distance of about fifty miles. 

 Among these points we may mention the vicinities of New 

 Market, Gladstone, Walker's Ford and Stapleton. 



The Richmond and Alleghany Railway from Lynchburg to 

 Rope Ferry bridge cuts the Arcbasan beds nearly at right angles 

 to their strike, and affords well defined exposures at or near 

 every station. About a mile and a half below the bridge on 

 the north side of the river, the contact of the Archaean rocks 

 (la) with a trough of Cambrian age overlying them may be 

 readily observed. 



The Norfolk and Western and the Richmond and Danville 

 railroads both afford some favorable points for observation in 

 this ancient group ; especially near Burkesville at the intersec- 

 tion of these lines, and at Lynchburg and Liberty on the 

 former, and near Amelia C. H., Boston and Danville on the 

 latter line. 



Cambrian, Primordial (No. I, Rogers), or Potsdam, 2a, b. — 

 Virginia affords rare facilities for studying this group, except 

 the Acadian epoch, 2a, the existence of which along this por- 

 tion of the Blue Ridge range has Dot been ascertained with 

 any certainty. If it be here it is not characterized by fossil 

 remains. Professor Rogers thus describes the rocks of this 

 group : " The rock, or group of rocks, which is frequently ex- 

 hibited in extensive exposures along the western side and base 

 of the Blue Ridge, more especially in the middle counties of 

 the valley, is usually a compact, rather fine-grained, white or 

 yellowish gray sandstone, where resting on the declivity of the 

 ridge, it presents a gentle inclination to the northwest — while 

 the subjacent and more ancient strata of the ridge, in almost 

 every instance, dip steeply to the southeast. In Page, Rock- 

 ingham, Augusta, Rockbridge (and Botetourt) counties this 

 group forms the irregular and broken range of hills lying im- 

 mediately at the foot of the main Blue Ridge, and sometimes 

 attaining an altitude little inferior to that of the main mountain. 

 A level regioD, sometimes of considerable breadth, and strewed 



