i 
: 
| 
; 
J. L. Campbell—Geology of Virginia. 485 
board) before the objective, instead of by a prism between the 
ocular and eye, he could not have been misled, since the 
uncolored image would serve to control the eye. 
Finally, the fourth conclusion (p. 196) is strictly true, ei 
as offensive. 
Johns Hopkins University, Sept. 20th, 1879. 
telescope the secondary spectrum becomes much less than half 
e 
Art. LV.—Geology of Virginia :—Baleony Falls. The Blue 
Ridge and its geological connections. Some theoretical considera- 
lions ; by J. L. CAMPBELL, Washington and Lee University. 
Blue Ridge at Balcony Falls, where the James River passes 
from the Valley to Piedmont Virginia. The canal from Lynch- 
Inspection. Reference was made to this point in a former paper 
(July No. of this Journal, pp. 22, 28), by way of illustration. 
T now propose to discuss some of its interesting features more 
Topography.—The accompanying map and section will serve 
to throw light upon both the topographical and the geological 
features of the locality. Leaving out of view a number of 
Irregular foot-ridges on the southeast side, we may regard the 
Am. Jour. Scr.—Tatrp Serres, Vor, XVIII, No. 108.—Dec., 1879. 
28 
