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W. M. Fontaine—Mesozoie Strata of Virginia. 27 
short distance south of the Appomatox River in Amelia 
County, and extends in a direction a little east of north to the 
_ vicinity of Chesterfield Station, in Caroline County, on the 
Richmond, Fredericksburg and Potomac Railroad, where it is 
overlapped by later formations. On the Chickahominy River, 
northwest of Richmond, this belt is broken by an interval of 
Azoic rocks three miles wide, which separates the northern from 
the southern portions. The southern portion alone yields coal, 
and as it differs somewhat from the northern portion, we may 
give it the distinctive name of the Richmond Coal Field, while 
the northern portion lying mainly in Hanover County, may be 
called the Hanover area. No doubt the two were once con- 
nected by at least their latest formed beds. Both sections of 
the belt bave suffered much from erosion, and we find here 
again the striking feature of the planing down of the yielding 
beds of the Mesozoic, to the same level with the most resistant 
Azoic strata. The coal field is separated from the Tertiary on 
the east by a belt of granite and gneissvid granite about twelve 
miles wide. This belt seems always to have formed the eastern 
border, cutting off the southern end of the coal field from com- 
munication with the open sea. It is by the sinking down of 
this granitic border to the north, that the Tertiary beds are 
enabled in that quarter to overlap the Mesozoic of the Hanover 
area. The northern end of the coal field proper sends finger- 
like projections into the Azoic, which are the deepest portions 
of troughs which have escaped erosion. Some of these are 
entirely isolated from the main field. They sometimes furnish 
very instructive sections, throwing light upon the geological 
history of the coal field. 
Still farther east, and differing in position from all the pre- 
ceding belts, we find two others geographically distinct, but 
geologically the same. These lie east of, and outside of the 
ic rocks, and are really a shore formation, which must have 
extended to the open sea, though the indications are that the — 
communication was very imperfect. Owing to their apparent 
Petersburg and extends along the eastern edge of the Azoic 
eastern side. In this quarter, the uppermost beds of the 
any rate, Professor Rogers states that a small patch of strata of 
the same character is exposed in the bed of the Nottaway River 
