STEVENSON, COAL BASIN OF COMMENTRY 
197 
when the Grande Couche began, and in all probability the bottom fell off 
very gradually southward. 
Any hypothesis to be satisfactory must account for deposits of rock above 
the Grande Couche. But before this matter can be taken up, some other 
features of the Pegauds area must be considered. 
Many of the observed irregularities in stratification are due to the manner 
of deposit; but there are others which were brought about after the rocks 
had been consolidated. 
Possible early erosion of the Grande Couche. 
The conditions observed in the Grande Couche within l’Esperance and 
Longeroux are perplexing, and the writer’s observations do not suffice for 
final explanation; no assistance can be obtained from the record as given 
by Fayol. 
In an exposure at the southerly end of l’Esperance the coal and its 
overlying shale have been planed off and the fine dark shales overlie it un- 
conformably; in the neighboring trench of Longeroux, the same condition 
is observed, except that the plane of contact rises westwardly. Midway 
in Longeroux and at a score of feet lower the coal has been cut off in the 
same way, but the fault features are not so distinct, as the overlying shales 
rest on the coal instead of meeting it with their edges; but this is evidently 
the same plane as that at the end of the trench, for that inclines southwardly. 
This faulting does not affect the Banc des Brouillages, the lowest portion 
of the Grande Couche, which is continuous from below the plane of faulting 
all the way up the wall and the fine dark shales rest against it with the same 
dip. 
The Grande Couche in FEsperance shows two broken folds; in Longe¬ 
roux, the bed is crushed and folded as shown in Figure 2 and Plate XIX, 
figure 2, the pressure as in l’Esperance having been in direction of the strike. 
In this Longeroux fold, a shale is involved of which no traces appear above 
the coal, and the fine dark shales, not sharing in the disturbance, thin out 
gradually on the jagged upper surface of the coal bed. The Banc des Brouil¬ 
lages does not seem to have been affected. That the coal had been con¬ 
solidated before the folding took place appears from the features already 
described on an earlier page. 
These disturbances were not contemporaneous. The folding is along 
the strike and the faulting along the dip. It is quite possible that the folding 
was due to a disturbance which brought the Grande Couche again to the 
surface and exposed it to erosion; in which case it would be the source 
of the pebbles seen in higher rocks. The top of the fold in Longeroux has 
