STEVENSON, COAL BASIN OF COMMENTRY 
171 
They were taken out whole only by careful picking away of the surrounding 
rock. Nor was any of them coated by material which could be regarded as 
the filling of a cavity; they were in direct contact throughout with the in¬ 
closing rock, as were the fragments of sandstone or of ordinary shale. Other 
observers have found pebbles giving clear evidence of contraction, but the 
writer is convinced that there are many pebbles which give no such evidence, 
which must have been torn from a bed of coal. This is not unimportant, 
for these pebbles have not always the same composition as the neighboring 
coals and some of them are almost lignitic. 1 
As one descends the stairway, he approaches the Grand Couclie and 
finds 
Feet Inches 
1. Shale .6 0 
This is hard, black, laminated and carries many films of bright 
coal; it is rich in carbon throughout. 
2. Shales .13 0 
3. Coal, Banc superieur, Banc du toit .6 0 
This consists of Cannel shale, 2 feet, 4 inches; Shale with films 
of coal, 1 foot 6 inches; Coal, 2 feet 2 inches. The top shale is 
decidedly bony, laminated in part and, as is usually the case with 
such shale, carries streaks of bright coal; the middle shale varies 
from almost wholly impure bright coal to almost wholly dark 
shale; while the coal below is of poor quality and broken by 
many clay partings. 
4. Banc des Chavais .6-7 0 
This, for the most part, is of very dark color, so that the miners 
call it the Banc Noir. As in Foret, it consists of transported 
fragments, varying from mere grains to blocks, one foot or more 
in diameter. Sandstone, gneiss, granite and quartz were seen, all 
waterworn, though some have the angles only rounded; there is 
much coal, especially in the upper part, so that the passage to 
No. 3 is nowhere abrupt. At one exposure, the upper portion is 
almost wholly coal, in which are imbedded occasional pebbles, 
several inches in diameter. The bottom foot or 15 inches is a 
dark shale passing gradually into the next subdivision. 
5. Coal, Banc intermediate .10 9 
This has a three-inch parting at 14 inches from the top. Mid¬ 
way in the trench, an exposure shows four feet of coal above ‘this 
parting, the increase being due to decrease in the Banc des 
• Chavais. The coal is very good throughout; it contains many 
partings, some of them composed largely of mineral charcoal 
(fusain). 
6. Banc des Roseaux .2-4 0 
Mostly argillaceous, but varying in composition as well as in thick¬ 
ness; the color is light gray, weathering yellowish; the bedding 
1 Fayol : CoTnrnentry, p. 16S. 
