72 
valley. Some years ago, I found glacial indications at the 
sources of the Potomac; among them a true Canadian boulder 
of red felspathic gneiss. Lately, in the same region, I found 
on the summit of the West Front of the Alleghany mountains, 
a series of drift deposits, mainly derived from Carboniferous 
rocks, and including fragments of coal, resting upon the 
upturned and shaved-off edges of Devonian (?) sandstone. 
In the valley of the Greenbriar river, west of these moun- 
tains, heavy deposits of drift appear at various points; and 
especially at the junction of the Greenbriar with New river, at 
Hinton, Va. In digging the foundations of depot buildings 
for the Chesapeake and Ohio Rail-Road, large surfaces of the 
Sub-Carboniferous limestone were laid bare, They are 
smoothed, polished, striated, and broken down on the edges, 
and covered with a mantle of drift twelve to fifteen feet thick. 
On a branch of the James river, at Covington, Va., I found 
the upturned edges of the slates of the Blue Ridge cut off by 
claciers, and bearing their load of drift. Like indications 
are visible along the Chesapeake and Ohio road, as far as the 
tunnel opening into the Greenbriar valley. This branch of 
James river rises on the east flank of the same range of 
mountains, and also southward from the head waters of the 
Potomac. 
These facts lead to very interesting inquiries. Did the 
glacier of the Greenbriar, after reaching New river, move on 
southward into the great valley of Virginia, and meet the 
glacier of James river moving along the same valley? Or 
did it turn westward, follow the valley of New river into the 
Kanawha, and then pass down this latter valley to join the 
ereat glacier of the Ohio? Possibly it divided and did 
both. 
These observations carry the southern limit of glaciers as 
far down as Lat. 37°30’ N. At and near Richmond, Va., I 
have seen long trains of boulders (small, white, and gravelly) 
streaming away in a north and south direction. I found, 
also, that the northern out-crop of the lower coal of the 
James river (Triassic) coal-field, had been torn up and carried 
over and deposited upon the upper and higher coal measures. 
Although signs of ancient glaciers are not so frequent and 
palpable south of the Potomac as north of it, yet I am per- 
suaded that by due inspection they can be found in places 
little imagined. 
Dr. STEVENS also madea communication, entitled “ Irregu- 
larities in the Floor of the Coal Measures of Eastern 
