W. M. Fontaine—Primordial Strata of Virginia. 425 
General Remarks and Conclusions. 
Having given the above brief indication of the possible rela- 
tions of the lower Primordial strata to each other, I will devote 
asmall] space to pointing out the apparent relations of these 
strata to the metamorphic eh rocks of the Blue Ridge. 
am aware of the fact that not enough has been Jes to justify 
in alt cases positive conclusions. 
my paper on the Blue Ridge of Virginia, published in the 
January and February Nos. of this Journal, I gave a deserip- 
tion of certain coarse syenites and granites, which, in the vi- 
cinity of Balcony Falls and the Peaks of Otter, compose a large 
portion of the Blue Ridge, and which appear farther to the east 
in the short ranges of Tobacco Row and No Business Moun- 
tains. From Ae? ee sha? aces = and wos Neto of 
country, belong to this system or to the slates, remains to be 
determined. These Laurentian rocks evide ently increase in 
their development ree the northeast portion of the State to 
the southwest. 
ying along and upon the eastern slopes of the syenites of 
the Blue Ridge, in the region of Balcony Falls, a formation 
of argillites occurs, which, in the of Wositke pera the entire 
Space up to the Primordial strata. Thes rocks are covered to 
the east by a series of mica slates, ectinta, gneisses, etc., dis- 
posed in a great synclinorium which has its axis in the vicinity 
_ of the Catoctin Montana This axis is oceupied by talcose 
limestones, quartzites, mica slates, hydromica esas ete., stand- 
ing nearly vertical. These latter strata in every respect bear a 
most striking resemblance to the rocks described by Prof: Dana 
as found in Berkshire Co., Mass. This entire belt of slaty, — 
metamorphic strata, is bounded on the east by a line drawn fro: 
northeast to southwest, and passing through a point feat aa or 
five miles west of Alexandria, the eastern m part of Louisa Co., 
and by Columbia, on James "River. It will be readily seen 
that these rocks have all the characteristics of the Green Moun- 
tain series. I think that.in this broad belt at least two systems 
waa one older than the Primordial strata, and the other com- 
of metamorphosed Silurian. The argillites of the Blue 
ai belong to sian: former. Whether these are of Laurentian 
uronian age, I cannot undertake, in the present lack of 
detailed raps to de mide Their unconformability with 
the coarse syenites apparently shows them to be of later forma- 
tion. How mu ach of the mica slates and sepa ies ear is of the 
same age with the argillites remains to be I need not 
