234 W. M. Fontaine—Mesozoic Strata of Virginia. 
etc., quite or lying scattered over the surface. Passing 
still farther west, we find the same material with the fragments 
of the Ficeesd es rocks becoming more abundant, and 
when we pass west of this field these coal rocks disappear, but 
we still have the other material. The Potsdam stones however 
do not pass westward over the whole Azoic area. They become 
confined to a belt along the James, in the upper course of that 
river. Ido not know what is their disposition on the Upper 
Appomatox, as I have not examined tbe country in that quarter. 
It is plain that this coarse drift is the product of the same force 
which formed the uppermost bed of the Mesozoic at Dutch Gap 
The belt of Azoic, with the included Richmond belt of re 
Mesozoic, which contains on its surface Potsdam stones mingled 
with the fragments of Azoic ioc is about twenty-five miles 
wide south of the James. It na s to ten or twelve miles 
near the northern end of the Pevamtausi Belt, on the North Anna. 
West of this the Azoic drift masses are still found on the sur- 
face, up to the Catoctin Mountains but no Potsdam stones. It 
is noteworthy that this drift is usually almost entirely quartz, 
often in blocks two and three feet thick, representing the quarta 
of the veins so common in some of the Azoic strata. The 
reason why we do not find more of the crystalline schists is, 
because the deep decay which had affected these rocks at the 
time of their erosion, presented to the eroding agent only fria- 
ble grits and bon ith the quartz veins in them standing in 
their original pos 
n the more eanaely localities where the Potsdam is no lon- 
ger tnad generally over the surface, I noticed that the bands’ 
these Potsdam stones along the ‘James do not follow the 
—— windings of the stream but pass directly across the 
They occur 150 to 200 feet above the river, and lie on 
sition the direction from which the eroding agent =, 
Sometimes, however, modern surface or stream erosion has 
cee these drift matters, as to cause them to appear to aoe 
from some other quarter than the west, which is their true 
source. This has misle rH, Stevens, who visited the 
Richmond Coal-field some . ago, and came to the conclu- 
sion that the mode of t rt was the movement of a glacier 
from the northward, in the t lacial Period. He states his views 
in a letter published in this Journal, Nov., 1873. 
