% 
] 
’ 
! 
J: Ia Campbell— Silurian Formation in Virginia. 29 
from Millboro to the Warm Springs, about three miles from the 
station at which the stage coaches leave the railroad, this forma- 
tion ma seen as an anticlinal arch, spanning the lower lime- 
stone of VI, in which the famous “ Blowing Cave” of Bath 
County is situated. Here the Calfpasture River has cut 
through a ridge and given a natural section along the base of 
which the stage-road passes, and where the Oriskany and Hel- 
derberg formations are well exposed, and, together with the 
Blowing Cave, present points of considerable scientific interest. 
Here, also, the meeting of the Oriskany, the upper member of 
the Silurian, with the Marcellus (?) shales, at the base of the 
orca may be distinctly pernarite on both ‘sibs of the 
ri 
The following table exhibits a comparison of the subdivis- 
ions in —_ portion of the Virginia st with the periods and 
n Professor Dana’s Manu: 
Silurian rocks of the Great Valley of fk drtaie with their sub- 
divisions, compared wi with equivalent epochs of 
Danas Manual, p. 142. 
3 , al 
3 Periods. Epochs, Rogeet Stele ee Sub- 
_|Oriskany 8 |Oriskany,  |No. VIL. | |Spirifer Sandsto 
a ike fsiorhay. : L. Helderberg. |No. VI. Encrinal — 
'S Salina. Salina. c | Calcareous es. 
E 5c| Niagara. No. V. 6 | Ferriferous Shales. 
ss 5d) Clinton. a |Shaly Sandstones, 
2, Niagara. ¢ | Upper Sand-rock, 
5 5a! Medina. _|No, IV. | 6 | Purple Shale and Sandstone. 
a | Conglomerate. 
hip esa | | ¢ | House Mt. Shales. 
Trenton. dal Tebniel: No. TL at le P n Limest ale 
* , a pat 
g Chazy. c Limestones. 
"= |Canadian. 3b | Quebec. No. IL {|b |Dolomitic Limesto 
| |3a/ Calciferous. ai ic Li 
(| g |Tron-bearing Shales. 
s 2b| Potsdam. 7 Scolithus Sandstones. 
3 ghee or a § cers) Spin ae 
eae Sal Acadian. | | /¢ | Middle Shales. 
|| @ | Lower Shales. 
Meta- (| c | Slates and Syenite Gneiss. 
2 mor- + |} | Bedded Syenite. 
§ Archzan. Archean. phic. (| a| Lower Sla 
me {|Igneous. | #| Eruptive Syenite. 
