174 
ANNALS NEW YORK ACADEMY OF SCIENCES 
then plunges abruptly to within eight feet of the Grande Couche, where the 
exposure ends. The two coals are said to unite at only a few feet beyond. 
Beginning at the stairway with a thickness of only two inches, this coal soon 
increases to a double bed, two or more feet thick, but thins again to barely 
one foot before reaching the Grande Couche. These variations are shown 
in the photograph. The interval between the coals, as measured on the face 
of the wall, without regard to dip, decreases from 70 feet to zero within 300 
feet. This is not a case of erosion; the thin white bands on the wall con¬ 
verge through disappearance of the intervening shales until almost in con¬ 
tact, and they, too, disappear where the little bed makes its abrupt plunge. 
Meanwhile the sandstone at the base of the Gres Noirs, overlying this 
coal bed, thickens until at the southerly end of the wall, it becomes the 
striking feature and it is said to rest directly on the Grande Couche at a few 
feet beyond the end of the exposure. 
Ascending the stairway at this end of the excavation, one finds, as shown 
in Plate XVII, figure 1, first the very light gray sandstone, not coarse, soft 
and holding many streaks or better irregular fragments of coal, some of 
which are several feet long and more than a foot thick. These coal patches 
are in no sense petty beds and are without definite form; some fade away 
at each end in a bunch of filaments; some terminate abruptly at both ends, 
while many are blunt at one end, broken up at the other. Above the sand¬ 
stone is a mass of dark, almost black shale, 10 to 30 feet thick, loaded with 
irregular sheets of coal and containing bodies of sandstone resembling that 
below. At some exposures this deposit might be described as coal with 
much shale, at others as shale with much coal. Its coal is good, similar to 
that from the Grande Couche; it occurs in streaks one half inch to several 
inches thick and frequently several feet long; some of the thicker streaks 
show partings; and the amount of coal is sufficient to justify mining,— the 
foreign matters being removed by washing. It is difficult to give a proper 
conception of the amount of coal or of the manner of its occurrence. The 
conditions are wholly unlike anything which the writer has seen elsewhere. 
There is no coal bed, there is only a commingling of shale and coal. Occa¬ 
sionally, there is passage from one to the other, but that is exceptional; the 
coal and shale are distinct. The conditions throughout suggest that here 
one is viewing the ruins of a coal bed, which had been removed from its 
place and redeposited with its associated shale. Above this black shale is 
a moderately coarse sandstone, weathering yellowish and apparently con¬ 
taining no coal. These two sandstones with the intervening shales may be 
taken as representing the Gres Noirs group of Fayol. 
Returning now to the lower level one finds himself on the basal sand¬ 
stone of the Gres Noirs at the foot of the stairway; but within a few steps 
