Campbell — Rogers 's Geology of the Virginias. 373 



outcroppings of 36, c, and 4a, 6. After passing Staunton this 

 line cuts 36 and c, for five miles, then runs for a few miles on 

 4a ; then before reaching Greenville it again runs upon 36, c, 

 which are well exposed in cuts and along streams to a point 

 within six miles of Lexington, where 4a becomes the country 

 rock and so continues to be until we reach the town, which is 

 built upon Trenton limestone. The river cliffs for five miles 

 above and below the railway bridge at this place, together with 

 the hills surrounding the town, and the flanks of the neighbor- 

 ing House Mountains, afford unsurpassed facilities for studying 

 both the Canadian and Trenton groups, and especially the 

 latter. 



The Manassas Gap railway, between Front Eoyal in Warren 

 county and Strasburg in Shenandoah county, crosses the trough 

 in which the Massanuttens rest at the extreme northeast termi- 

 nus of that range of mountains, affording not only views of the 

 Trenton foundation, but also of the superstructure of Medina 

 and Clinton sandstones which form the crest of the historic 

 Fort Mountain. 



The Shenandoah Valley railway starts upon 4a, at Hagers- 

 town, Md., crosses the Potomac on a bridge, the abutments of 

 which are 36. From this point to its terminus at Eoanoke 

 City, in Eoanoke county, Va., its bed is composed almost en- 

 tirely of Canadian, with a few patches of Cambrian and con- 

 siderable areas of local drift. The road at some points affords 

 opportunities for interesting observations. The cliffs of the 

 Potomac at Shepherdstown, the cuts near Charlestown and the 

 margins of both branches of the Shenandoah near Front Eoyal, 

 bring into view well-defined beds of 36, c. At Luray, the sta- 

 tion and the greater part of the village appear to rest upon 36, 

 while the entrance to the caverns is, as far as we have been 

 able to examine the locality, most probably in a hill composed 

 of 3c (Chazy). Weyer's Cave, in the eastern corner of 

 Augusta county, has about the same geological features and 

 surroundings as the Luray caverns. Waynesboro is close to 

 the line of connection between the Cambrian and the Canadian 

 groups, and is a favorable point at which to study the structures 

 of both, while the neighboring tunnel through the Blue Eidge 

 shows the relation of the Archeean and Cambrian rocks with 

 their actual contact at the western extremity of the tunnel, 

 where apparent conformity exists between the two series. The 

 Natural Bridge and the cliffs about Buchanan are both favor- 

 able localities for examining beds of 3a, 36, and 3c — all being 

 well exposed in the vicinity. 



From Balcony Falls to Eagle Eock, in Botetourt county, the 

 Eichmond and Alleghany railway crosses the strike of the valley 

 limestones in such a way as to open some well-defined sections. 



