STEVENSON, COAL BASIN OF COMMENTRY 
165 
that given by Fayol in the Reunion, etc.; this shows also the outcrops of the 
coals as well as that of the strange mass, known as the Banc de Sainte-Aline. 
The writer’s observations were confined wholly to the area of les Pegauds. 
The principal coal bed is the Grande Couche; above that, at varying dis¬ 
tance, is a coal-bearing deposit known as the Gres Noirs, and still higher is 
another, that of les Pourrats. These are all one bed on the eastern side near 
the southern limit of the coal, but they separate westwardly, and toward the 
Montassiege side the vertical interval is several hundred feet. The Grande 
Couche, now reached by a deep shaft, was mined for many years in open 
quarries, or tranchees, beginning at the crop and following the coal by 
removal of cover. At the depth of 40 to 60 meters, stripping ceased and 
stopes were driven on the coal. These quarries are almost continuous along 
the thicker portion of the outcrop and are of vast extent. The photograph 
of the Tranchee de Foret (Plate XV, figure 1) suffices to show the general 
character, though it is one of the narrower and less imposing. Several of 
the quarries have been abandoned and they are utilized as receptacles of 
waste from the mine and washeries as well as from the iron works in the city 
of Commentry. 
Description of the Openings. 
The great quarries or trenches follow the curved outcrop of the Grande 
Couche; those on the eastern side are, for the greater part, still in good con¬ 
dition and mining is carried on to some extent in all but one. It is best in the 
description to begin midway and to study first the trenches on the eastern 
side; afterwards to examine those on the westerly side, where mining opera¬ 
tions have ceased. 
Tranchee de Saint-Edmond. i 
The Tranchee de Saint-Edmond, beginning at a few rods west from the 
present mine, is 160 feet deep and several hundred feet long. No serious 
work has been done in it for many years, and the waste dump at the west end 
has cut off much of its original length. The width at bottom varies from 
somewhat more than 100 feet at the west to barely 50 feet at the east end. 
The Grande Couche is covered by the dump at the west but is still to be 
seen in the tunnel leading into the Grande Tranchee, and the top of the bed 
is reached on the floor at the foot of the south wall. The dip here is approxi¬ 
mately S. 30° W., and the wall, consisting of shale and sandstone, is sheer 
from bottom to top. At this end, a succession of sandstones, with thinner 
