145

No. 3 opening started as an adit, partly on the seam and
partly in the glacial till, but with the increasing dip of the coal
the adit developed into a slope, as shown in Figure 20.

Coal Seam. The Wilson seam varies from 4 feet to 18
feet in thickness where measured, but it is not certain that the
full thickness is exposed where the smaller measurement was
obtained. It is certain, however, that the seam is of varying
thickness, and that the maximum figure given above does not
represent the true average.

The floor is a green, fine to medium-grained sandstone, con-
taining scattered, well rounded pebbles up to an inch in diameter.
Under the microscope the sand grains are seen to consist of
rounded volcanic fragments, with quartz and decomposed felds-
par grains, in a calcareous cement.

The seam itself, of which a diagrammatic section is given
in Figure 21, is best exposed in No. 1 opening, and was there
sectioned and sampled. It is divided into two benches by a 5-
inch band of soft, grey sandstone, occurring about 5 feet above
the floor. At the base of the seam are usually found lenticular
bands of granular, yellowish-grey, soft clay shale; but in some
places the coal rests directly on the sandstone, or is separated
from it by a layer of bone or by a bedded vein of calcite. In other
places, bands of the same soft, plastic, clay shale occur in the
lower part of the seam. The lower bench is dirty and of inferior
quality, as shown by the analyses of the coal. The upper bench,
about 12 feet thick, is composed almost wholly of coal in several
layers, not all of the same quality. The upper part of the upper
bench is crushed, dirty, and poor looking, and the analysis of
this portion runs 37 per cent ash.

The roof of the seam is a greenish, medium-grained sand-
stone, more pebbly than the floor, and in places almost a con-
glomerate.

In this opening (No. 1) the seam shows no evidence of local
thickening due to folding, the laminations being continuous and
even; but a slight amount of thickening due to faulting occurs.
The type of faulting is illustrated in Figure 22. The seam shows
strong, continuous slickensides, parallel to the bedding, which
are probably due to slight differential movements caused by the