135

Notes on Mining. The tunnel and slope, Figure 12, give
an opportunity of judging as to the qualities of the seam for
mining purposes. Unless the whole seam is mined and the prod-
uct washed free from dirt, the coal to be depended on is that in the
so-called 25-inch bench, in tht upper part of the seam. The
lower 10 inches of this are noticeably the better, and more free
from bone, some streaks of which occur in the upper part; but
the good part of this 25 inches cannot be mined separately.
From the bottom of this bench, at least 40 inches must be mined
above to the roof, which would readily stand, with props and
lagging every 4 or 5 feet. The roof holds well, and nowhere in
the tunnel it had sagged more than one foot. No caps are bent,
and there is little or no weight on the lagging, except for occa-
sional spalls due to slickensiding. Pillars in the seam could doubt-
less be robbed with safety, as the roof now stands 8 feet wide
rib to rib. There is no slumping from the sides, nor any trace
of swelling in the floor. The condition of the coal is the same in
the portion under water as in that exposed to the air. The coal
is as firm on the rib as at 2 feet in, and evidently does not carry
any extra weight of roof on account of the openings having been
made, as the roof supports itself right across. Water comes
into the opening only through occasional joints, and it is probable
that a mine on the seam would be dry and perhaps dusty.

Siructure. Although only exposed in the streams and pros-
pect openings, enough outcrops have been observed to allow
of the general structure of the rocks in this vicinity being made
out fairly accurately. Wawa creek flows along an anticlinal
axis, on which close local folding accompanied by some overthrust
faulting has taken place. The compressed anticline exposed in
the northwest and southeast walls of No. 1 shaft is sketched in
Figure 13. The axis of this fold may be traced in the roof of
the drift from this shaft and is seen to bend ina flatS curve. It
is quite possible that minor faulting further complicates the seam.

In the opening shown in Figure 12, consisting of a tunnel,
slope, winze, and raise, it is shown clearly that the two apparent
seams are parts of the same seam repeated by faulting. The
geological section sketched in the figure is well exposed on the
northwest wall of the tunnel, slope, and winze, and requires little