Aug., 1890. 
THE DOVER COALFIELD. 
173 
overlaid by shales, grits, sandstones, and quartzites, above 
which come the coal measures, which are said to be richest 
in the European continent, having a great number of seams 
of coal, ranging in thickness from a few inches to as much as 
six feet. The coal is of a somewhat schistose character, some 
being composed even of extremely thin laminae, whilst other 
varieties are compact, and others again earthy and pulveru¬ 
lent, and there is also a wide range in its nature as a com¬ 
bustible, all species from cannel to anthracite being found. 
There is one class of coals, known as “ houille maigre,” 
“ terre-houille,” or “ teroule,” which contains a large per¬ 
centage of ferruginous clay, found amongst the inferior 
measures, and which is of very slow combustion. 
We will now, taking our start from the Liege district, 
follow the coal measures along the left bank of the Meuse. 
They gradually decrease in extent, and are at last interrupted 
by the transverse valley of the Sanson. We find them again 
at Charleroi, but their area is here reduced from about 
12,000m. to 8,000m. The coal measures cross the central 
part of Belgium, and they are struck to the west of Mons, 
where they are partly buried beneath more recent beds ; and, 
following them towards the French frontier to the west of 
Dour and Elonges, they dip beneath the cretaceous rocks. At 
Anzin they are found at a depth of 80m., the depth increas¬ 
ing as we go towards Denain, Aniclie, Douai, Lens, and 
Betliune, where as much as 150m. of cretaceous strata over- 
lie the coal measures. Then we come to the Valenciennes 
coalfield, which has been traced to within thirty miles of 
Calais at a depth of 1,104ft. In the Pas de Calais the con¬ 
cealed coalfield has been pretty thoroughly explored by means 
of numerous borings and pits. It occupies a constricted and 
not very productive area, cut off both on the north and on the 
south by Devonian rocks, which are found to lie immediately 
beneath the chalk. 
Before attempting to follow the coal measures beneath the 
Channel, let us go back to Belgium, in order to obtain a clear 
idea of the nature of this once continuous coalfield. 
The coal formation of this area occupies a long, narrow, 
synclinal trough, in which it has become more and more 
closely contracted, so that in the central and deeper pits the 
boundaries of the upper beds are said to form concentrically 
closed lines. 
One of the central areas which received the latest deposits 
was that of Mons, of which the upper and more recent beds, 
characterised by a special quality of coal, known as “flenus,” 
(cannel ?) are hardly found anywhere else. So the conclusion 
