_--As previously stated, the rock broke better on the
south than on the north side, where there were several slides, and
considerable excavation had to be taken out beyond the neat line required
in the specifications. The worst slide occurred at midnight on July 3d,
1909, at about Station 188 + 50. The last blast, to complete the excavation
to sub-grade at this point, had been fired in the afternoon of the same
day, and the mucking was practically completed. Great care had been taken
in excavating near this point, as it was evident that the rock was not of a
very stable character, but, when the excavation had been completed, it was
thought that the rock remaining in place would stand. The volume of
material brought down by this slide amounted to about 200 cu. yd. The rock
on the south side broke very well, and there were no slides of any
consequence.

The drill holes were laid out by the blaster, and the general method of
drilling for different classes of work was as follows: In breaking down,
the holes were started about 8 ft. apart, on a slight batter, so that at
the bottom they would be considerably less than 8 ft. apart. They were
drilled about 10 ft. deep, and blasting logs were used, as it was necessary
to load quite heavily in order to lift the material and start the cut.
After the cut had been made, side holes were shot to widen out sufficiently
to start another cut.

After a side cut about 20 ft. deep had been made, the side holes were
drilled 20 ft. deep, and the holes were loaded and tamped for the full
20-ft. cut. Under the terms of the specifications, the contractor was
required to complete the excavation on the sides by drilling broaching
holes.

The maximum length of drill steel was about 20 ft., and, where the
excavation plane of broaching was more than 20 ft. in depth, the contractor
was permitted to start the holes back of the broaching line, in order to
allow for setting up the drills on the second lift. A distance of about 8
in. was usually allowed for setting up a drill. The broaching line was
painted on the surface of the rock in advance of the drilling, and the
batter of the drill was tested with a specially designed hand-level in
which the bubble came to a central position when the face of the level was
on the required batter. Holes were also drilled in front of this broaching
line, and, when the excavation had been taken out to within about 6 ft. in
front of it, the holes immediately in front