Campbell — Rogers's Geology of the Virginias. 365 



profusely with fragments of this rock, in general intervenes be- 

 tween the rugged hills and the first exposures of the valley 



limestones In many instances two, sometimes three, 



ranges of hills are interposed between the limestones and what 

 may be considered the termination of the rocks of the Blue 

 Kidge." Of the higher beds of these sandstones — the more 

 purely siliceous — he says: "In nearly all the exposures from 

 Balcony Falls (in Bockbridge county) to Thornton's Gap (in 

 Page county) as well as at various other places it exhibits 

 vague fucoidal and zoophytic impressions on the surfaces of 

 bedding, together with innumerable markings at right-angles 

 to the stratification, penetrating in straight lines to great depths 

 in the rock, and from their frequency and parallelism deter- 

 mining its cleavage in nearly vertical planes. These markings 

 are of a flattened cylindrical form, from -|-th to T Vth of an inch 

 broad, giving the surface of the fractured rock a ribbed appear- 

 ance, and resembling perforations made in sand which have 

 been subsequently filled up, without destroying the distinct- 

 ness of the original impressions" (pp. 167, 168). This is his 

 account of the Scolithus linearis. 



" At Harper's Ferry and for some distance south, where the 

 altered character of the sandstones and slates of this formation 

 renders it occasionally difficult to recognize the true dip, and 

 even to identify the rock itself, an eastern declination is almost 

 uniformly observed, the slates forming a portion of the bed of 

 the Shenandoah, dipping beneath the sandstone which rises in 

 bold cliffs along its eastern margin, while the limestone of for- 

 mation II (3a, b), dips in the same direction beneath the slate, 

 thus pointing to an inversion extending entirely through for- 

 mation I, and even affecting to a great distance the rocks of 

 formation II ... . At Balcony Falls, where the western clips 

 are preserved throughout a large part of the thickness of this 

 formation, the most favorable opportunities are presented for 

 studying the composition and marking the arrangement of 

 these rocks. The formation here rests upon igneous rocks, 

 chiefly of the syenitic character, which in this place form the 

 main axis of the Blue Bidge. These are well seen in traveling 

 along the tow path of the canal (now the B. & A. Bailway) which 

 follows the course of the river through the wild and beautiful 

 gorge by which it makes its way from the valley eastward. As 

 we approach the western termination of the pass, we mark 

 the commencement of the rocks of formation I, which are seen 

 on the side of the canal (railroad) lying on the syenitic mass 

 with a northwest dip. The lowest stratum, or that in contact 

 with the syenite, is a brownish decomposing slate, evidently 

 much altered by its proximity to the igneous rock beneath ; 

 next is grayish and reddish sandstone ; then a slate similar to 



