Oct., 1890. 
THE DOVER COALFIELD. 
281 
coal measures seem to surround the limestone pretty regularly, 
almost as though it had stood up whilst they were being 
formed as a pre-existent cape or promontory. Having crossed 
the Belgian areas of Beaudour, Hautrages, and Pommeroeul, 
where the coal measures lie at too great a depth to be work¬ 
able, we follow them into France to the west. 
The question now arises, Do the well-known beds found to 
the south correspond with the, comparatively speaking, lesser 
known ones of the north ? If they do, then the lower beds 
have completely changed their character ; at Sirault and Ber- 
nissart they are anthracitic, and the northern outcrops are 
much more anthracitic than those found on the south. The 
true anthracites, which are found near the northern boundary 
of the Charleroi area, are not found on the southern boundary, 
where the last workable coals are bituminous and cannel. In 
France, at Hergnies, Fresnes, and Vicoigne the coals, again, 
are true anthracites, which are nowhere found on the south 
boundary. The fact is, however, it is said, that we do not as 
yet know enough about the causes which have determined 
the various qualities of coal—we can but ascribe them to 
metamorphism, which by a gradual process of condensation 
has, as we have observed, produced a succession from cannel 
through bituminous coal to anthracite ; but when we find, as 
we seem to do in the area in question, a single bed of coal 
changing its character, in the course of a short distance, from 
bituminous to anthracite coal, we are in the presence of a fact 
which is by no means easy to explain. 
In the area extending from Valenciennes to Douai the coal 
measures lie in three divisions, the anthracites being, as else¬ 
where, at the bottom, at Vieux Conde, Hergnies, Fresnes, 
and Vicoigne; the coal is semi-bituminous at Anzin, and 
bituminous at Denain, Lourches, and to the south of Aniche. 
The anthracites are found to occupy a large area on the whole 
of the northern boundary of the basin. From the axis of the 
area to the northern limit all the known coals are anthracitic. 
The passage is progressive from true anthracites, which form 
the lowest and oldest beds, up through coals which become 
more and more gaseous in character. The bituminous coals 
are found on the southern side of the basin, and there is no 
outcrop of the anthracites. This anomaly has been explained 
by the presence of a fault which runs parallel to the long axis 
of the vallev from S. Saulve and Anzin to Denain and Abscon. 
•/ 
which cuts the basin into two portions, the northern, 
as we have seen, containing the anthracites and allied coals, 
and the southern the bituminous coals. 
M. Dormoy supposed that an upheaval of the strata broke 
the coal basin in two, following its longer axis, and raised one 
