W. M._Fontaine—Geology of the Blue Ridge. 17 
Mountains, these hills, and the Blue Ridge at Harper's Ferry, 
are each the result, in part, of such local changes producing 
elevation, but mainly of unequal erosion. The normal slates 
have been eroded to a much greater extent than the more highly 
metamorphosed rocks, and these latter have been left standing 
up in connected ridges. 
The entire distance from Point of Rocks to Harper’s Ferry, 
on the Maryland side, is apparently occupied by the argillites. 
Professor Wm. B. Rogers states, however, that on the Virginia 
side a narrow tongue of gneiss is found at the eastern base of 
“Short Hill,” near the center of the tract. This is the northern 
termination of a triangular area of gneiss which passes through 
Virginia along the eastern base of the Blue idge. A narrow 
belt of steatite and serpentine is also found in Loudon County, 
enclosed in hydromica or tale slates, and apparently pass into 
them by insensible gradations. 
Resuming our detailed investigations at the eastern base of 
the Blue Ridge on the Maryland side, at Harper's Ferry, we 
still find the argillites forming the principal rock, and here also 
name it in the absence of any analysis of the materials. As it 
eruptive igneous material. e principal component is a 
steenish-gray, rather waxy-looking amorphous base, having a 
hardness of two and a half, and a somewhat greasy feel. Im- 
bedded in this material occur rounded shot-like particles of 
quartz as large as a garden pea. They have various colors, 
pink, bluish, and white, the former predominating. The luster 
of the quartz is waxy. ‘The nodules sometimes almost disap- 
