OF THE APPALACHIAN CHAIN. 493 



daysburg, and ranging west of the centre of Sinking and Nittany 

 valleys, and through the middle of Nippenose valley, terminates 

 south of the Allegheny mountain, a number of miles northeast 

 of Pennsboro'. It thus embraces, in its long and gentle sweep, 

 a distance of about one hundred and twenty miles. For many 

 miles of its length, at each extremity, where it lifts only the mid- 

 dle Appalachian rocks, it displays simply a gentle normal flexure ; 

 but nearer the middle of the line, where it elevates lower and lower 

 formations, and finally brings to the surface the great Appalachian 

 limestone, the arch gradually steepens, until it embraces a verti- 

 cal, and occasionally an inverted dip, along the Bald Eagle 

 mountain, from the Little Juniata to Bellefonte. • 



The Jackson's mountain axis commences near the northwest- 

 ern flank of the Fork mountain, in Pendleton county, Virginia, 

 and continues in a nearly straight direction in Jackson's moun- 

 tain, and the anticlinal valley of the Warm and Hot Springs, as 

 far as Jackson's river, in the neighborhood of Covington, This 

 comprises a length of about seventy miles. Traced from its north- 

 eastern extremity to within a few miles of the first exposure of 

 the lower Appalachian limestone, the mountain continues single, 

 and displays a normal, but regularly increasing arch, with a steep- 

 ening northwest dip. But further towards the southwest, from 

 the commencement of the anticlinal valley, in which the limestone 

 rises, to the lower end of the Falling Spring valley, the mountain 

 divides itself into two ridges, that on the northwest exhibiting 

 both perpendicular and inverted dips. Beyond the Falling Spring, 

 the valley rapidly closes up again by the subsidence of the axis, 

 and at Jackson's river nothing remains of this remarkable range 

 but a low ridge, composed of the higher rocks, arching over in a 

 moderately obtuse normal flexure. 



The Wolf creek axis, in Virginia, rises near the head of Stony 

 creek, a little southeast of Peters's mountain, and ranges along 

 the southeast side of Peters's, and the northwest side of Wolf 

 creek mountain, and Rich mountain, for a distance of between 

 seventy and eighty miles. Throughout nearly the v/hole of its 

 length, this axis lies in the lower Appalachian limestone, in which 

 there is an inversion of the dip on the northwest side of the axis- 



