W. M. Fontaine—Mesozoic Strata of Virginia. 153 
most beds pass, as it appears, up into the strata which occupy 
the border belts, and which here overlap, as stated before, this 
area. I have not seen any similar beds of stones, on the west 
side of the Richmond Coal field, and do not think that they 
exist there, though my observations are not extensive enough 
to decide the question positively. The lower and middle por- 
tions of the series are much like the upper series of the Rich- 
mond Coal field. They contain some thin films of coal, and 
some plants, too poorly preserved to be of much value in deter- 
mining age, though so far as their evidence is to be taken, the 
series is certainly younger than the Richmond coal-bearing 
strata. A large amount of drifted vegetation, principally 
trunks and limbs of coniferous trees, now changed to lignite, or 
silicified, is found especially in the upper beds. The amount 
eaped up at certain horizons, is sufficient to give the appear- 
ance of small, locally developed coal seams. 
The Fredericksburg Belt.—In this, also, we may recognize two 
series, a lower, about 150 feet thick, and an upper, still thicker. 
Both vary so much in the composition and structure of the 
beds, that it is difficult to give any correct idea of them with- 
out going into details, which would require too much space. 
The lower series, however, is more constant in composition, 
and may be generally recognized by its physical features, 
which is not the case with the upper. It is composed mainly 
of a curious sort of sandstone (Rogers’ feldspathic sandstone) 
which possesses very little coherence. is 1s due to the fact 
that it is mainly composed of grains of sand, usually fine, sur- 
rounded by a non-plastic white earth, resembling kaolin. is 
1s a composition which indicates that the sorting action of water 
has not been brought into play. This is farther indicated by 
the structure of the mass, which is usually affected with false 
bedding, and often resembles a mass of agglutinated sand. The 
panes of the false bedding are very short, and shift rapidly. 
_ The strata lie nearly horizontal, inclining slightly to the south- 
_ east. Small stones are often scattered through the mass, and 
beds, nests, or pockets, of larger stones, occur at different 
_ horizons. These stones are sometimes four to six inches in 
_ diameter. All the stones are either quartz, which is most 
abundant, or Potsdam quartzite. The lower portion is, on 
the whole, more siliceous and coarser. The upper part is 
often a fine-grained powdery mixture, of siliceous matter and 
kaolin, which shows very sudden changes of texture and a 
and northwest are mica slates, argillites, ete., which in decom- 
posing yield yellow, reddish, and bluish clays, and yellowish or 
