STEVENSON, COAL BASIN OF COMMENTRY 
179 
The coal here is apparently the upper portion of the bed; but the plane 
of fault is at least 25 feet higher than in the trial pit, so that it had a some¬ 
what rapid fall southwardly. That the plane declines in that direction is 
very clear, for the coal soon drops below the floor of the extension and 
thence to its beginning one walks only on the dark shales. The relation 
of this exposure to that on the other side of the wall in l’Esperance was not 
ascertained, but judging from the interval to the bottom of the Glissement 
above, the exposure in l’Esperance is probably a little higher. 
Returning now to the beginning of the extension, if one climb to an open¬ 
ing in the Brouillages, about 25 feet, and look across and along this portion 
of the trench, he finds the l’Esperance convergence repeated but in different 
rocks. There, the light gray shales or fine sands, derived from the Montas- 
siege side, gradually disappear and the Gres Noirs gray sandstone comes 
down to the Grande Couehe; here, several hundreds of meters away on the 
outcrop, a similar change takes place, but in the fine-grained dark shales 
derived from the Longeroux region. It is seen partly in Plate XIX, figure 
2. As the shales decrease, the white lines converge in some instances, fade 
out in others, until, instead of 75 or 80 feet, one finds not more than six feet 
between the Gres Noirs and the jagged top of the Grande Couehe. The 
top of the coal bed at this place, the deep pit, is below the plane of faulting. 
The conditions are such that in any ordinary locality, one would conclude 
at once that here is the thinning of deposits against a shore line. 
The Glissement de l’Esperance is well shown in the northerly wall of 
Longeroux. The wffiole of the upper part was laid bare at this end, but the 
exposure is no longer very distinct on the easterly side, as the debris has been 
covered largely by vegetation. The width at the top is estimated at 450 
feet — it may be somewhat more. Perhaps one third, above, has been 
removed in making the upper platform on the west side, but the whole mass 
on the easterly side, so far as spared by erosion, remains and is sufficiently 
exposed to give a fair conception of the relations. The features of the 
westerly side are shown in Plate XX, figure 2. 
The rocks occupying the trough are in marked contrast with the dark 
shales alongside; they are very light in color, mostly sandstones, with at least 
one bed holding lines of pebbles which, as seen 100 feet away, are from one 
to three inches long. The beds within the trough are very sharply flexed 
on the westerly side, but the bending is less beyond the axis of the syncline, 
and on the easterly side the beds are quite regular with comparatively gentle 
westerly dip. The contact on this side is not shown fully, as the wall is less 
abrupt; debris has accumulated and some of the features are obscure. But 
the deposit reaches to or very nearly to the Banc des Brouillages, which is 
well shown at 25 feet away with dip of from 45 to 55 degrees toward the 
