180 
ANNALS NEW YORK ACADEMY OF SCIENCES 
trough. It is clear that some of the light-colored beds terminate against the 
easterly wall of the trough and that the higher beds form a syncline with 
gentle dip on that side. Whatever the origin of the material may have 
been, the greater mass was deposited on the westerly side and whatever 
the cause of the folding may have been, the resistance was especially strong 
on that side. The only locality, outside of the trough, where rock of this 
type was seen, is at the extreme northwest corner of the basin; there, in a 
railroad cut, near the station of Chamblet-Neris one finds a precisely similar 
rock, holding lines of pebbles arranged as are those in Longeroux. 
The bottom margin of the trough is well shown to beyond the middle, 
and the light colored rocks rest on the dark shales which are as little dis¬ 
turbed as are those in corresponding position within FEsperance. But on 
the easterly side of the extension, the shales, resting conformably against the 
Brouillages, have, in many layers, slaty cleavage, the surfaces being divided 
into rhomboids and thoroughly polished. On the westerly side, these shales, 
as the photograph shows, are sharply flexed and one of the folds is broken, 
with an overthrust fault as the result. The gray sandstone and black shales 
of the Gres Noirs share in this disturbance, the folds appearing in Plate 
XVIII, figure 2 and Plate XIX, figure 2 being just beyond the limit at the 
left of this photograph. 
A cross section is shown in a cliff between photographs, Plate XIX, 
figure 2, and Plate XIX, figure 2, where the dip is from 25 to 40 degrees. 
The noteworthy feature there is the complicated folding in some beds, 
shared to very limited degree by those adjoining. A faisceau of three 
beds, the middle one much lighter in color than the others, is seriously 
distorted, the middle one being closely folded on itself at one spot. As the 
wall is sheer, the beds cannot be examined and one may not be certain 
whether the distortion was due to a slide when the rocks were unconsoli¬ 
dated or to the more yielding nature of their materials, allowing them to 
receive a disproportionate share of the pressure during folding. The latter 
suggestion appears the more probable, as traces of the swelling are traceable 
in the adjoining beds. 
It is deserving of note that though the disturbance sufficed to push the 
Qres Noirs into recumbent folds, to induce slaty cleavage and slickensided 
surfaces in the dark shales as well as in the black shales of the Gres Noirs, 
yet the coal in the latter is fat with long flame; and the same is true of the 
Grande Couche, 1 which, in all probability had already suffered severe dis¬ 
turbance. 
In climbing out of Longeroux trench by the easterly wall, one is con- 
1 Fayol: Commentry, p. 24. 
