368 Campbell — Rogers's Geology of the Virginias. 



Waynesboro, Vesuvius, Loch Laird and Buchanan, are worthy 

 of note. Then Balcony Falls, already mentioned, and Buford's 

 on the Norfolk & Western railway in Bedford county. 



Valley Limestones — No. II {Canadian, 3a, b, c). — Under 

 this division Prof. Rogers in his State Reports embraces what 

 is now recognized as the Canadian group (3a, b, c), and the 

 Trenton Limestone (4a). But in his notes, prepared for Mac- 

 farlane's Guide, he gives the latter its true place. We know of 

 no region in this country which offers a more extensive or bet- 

 ter defined display of this important geological group than the 

 "Great Valley of Virginia." This valley occupies a belt ex- 

 tending from the Potomac on the N.E. to the line of Tennessee 

 on the S.W., a distance of about 340 miles, with a breadth 

 varying from 15. to 25 miles, giving an area not much if any 

 less than 6,000 square miles. We here quote Prof. Rogers. 

 " The extensive zone comprehended under this title embraces 

 all that portion of the State having for its eastern boundary the 

 western slope of the Blue Ridge and its inflected continuation 

 the Poplar Camp and Iron Mountains, and for its western, the 

 Little North, and a portion of Big North Mountain, with the 

 southern portion of the former, Caldwell's and Brushy Moun- 

 tains ; and, near its southwestern termination, . . . the exten- 

 sion of Walker's Mountain " (p. 203). ..." From the Po- 

 tomac southward nearly to the Rockbridge line, it presents the 

 forms of two belts, separated by an intervening tract of vari- 

 able width, formed of the next or several of the next superior 

 formations. As far south as the northern termination of 

 Massanutten range, the dividing band is composed exclusively 

 of the group of slaty rocks constituting formation III, (46, c). 

 Farther south these mountains bear aloft still higher forma- 

 tions, resting upon a basis of the slates, and broadly skirted by 

 them on either side; and again, after the termination of these 

 ridges in the peak near Keezletown, the same zone of slate 

 continues its course toward the south, gradually diminishing 

 in breadth until it eventually disappears. Similar interruptions 

 in the continuity of the limestone rocks are produced by the 

 Short's Hill, Purgatory and other mountains toward the S.W. 

 portions of the valley The prevailing dip of the lime- 

 stone along its eastern margin, where it joins the shales of 

 formation I, is to the southeast. Indeed but few instances 

 occur in the State in which this rock is seen reposing in its 

 natural position upon these older strata. As might be inferred 

 from the general prevalence of this inversion in the vicinity of 

 the Blue Ridge, the natural causes by which it was brought 

 about exerted a powerful influence upon the position of all the 

 rocks of the valley, and in some instances would seem to have 

 propagated a like inversion entirely across this zone and even 



