STEVENSON, COAL BASIN OF COMMENTRY 
181 
stantly on the Banc des Brouillages, which exhibits the same features as in 
Foret and l’Esperanee; but some of the sandstone layers are coarser than 
any observed in those trenches and contain abundant remains of plants — 
chiefly fragments of stems with the cortex converted into coal. These rock 
layers are light colored in all of the trenches and are not bituminous; those 
which from a distance seem to be dark colored are found on closer examina¬ 
tion to owe their color only to the presence of carbonized fragments, not to 
diffused bituminous matter; the mineral portion is as light in color as in the 
other layers. 
Near the top, at the southerly end of this trench, one finds the Glissement 
once more, its upper portion being exposed in a recently opened quarry. 
At the northerly end of the trench it seems probable that the trough involved 
the highest sandstone of the Gres Noirs; but at this end the matter is placed 
beyond doubt, for the yellow sandstone forms the westerly wall of the trough, 
thus showing that the trough did not originate before the middle division of 
Commentry measures had been deposited completely. The Glissement 
rock is almost wholly sandstone with dip of not more than 15 degrees south- 
eastwardly, but slightly more at the westerly wall. The yellow sandstone 
is hardly disturbed at the contact and is unaffected at 10 feet away. There 
is no exposure beyond the immediate vicinity of this quarry, but the topog¬ 
raphy southward is such that the Glissement sandstone must extend in 
that direction and that it reaches a higher level than at the quarry, so that 
there the wall of the trough must reach up into the shales which overlie the 
yellow sandstone. 
As one ascends the stairway to the quarry, he sees a deep excavation 
on the easterly side, cutting into the course of an old stream, which dug a 
narrow valley, now filled with sand and gravel belonging to the recent 
deposit, covering this part of the Commentry basin to the depth of 10 to 20 
feet. 
Leaving the Longeroux trench at the quarry one reaches, at about one 
fourth of a mile, an opening into a still higher coal bed, whose relation to 
the other deposits could not be determined. The pit is, by barometer, 280 
feet above the Grande Couche, but the direction is considerably off the 
strike and the irregularity of dip is such that no calculation of vertical 
distance can be made. The bed seems to be not less than 75 feet above 
the top of the Gres Noirs group. The coal is reported to vary between three 
and seven feet and it is associated with a clay shale, drab but weathering 
yellowish. This is the highest bed examined by the writer. 
In following the road from this pit westwardly to the present mine, one 
finds no exposures; but along an old road, a little northward, a good exhibi¬ 
tion of the yellow sandstone with southerly dip of 25 degrees, was seen 
