Uncle Sylvester cast a resigned glance out of the window. "Oh,
yes--certainly; it isn't much. You see at one time I was in the habit of
making long monotonous journeys, and they were often exhausting, and,"
he added, becoming wearied as if at the recollection, "always dreadfully
tiresome. As the trail was sometimes very uncertain and dangerous, I
rode a very surefooted mule that could go anywhere where there was space
big enough to set her small hoofs upon. One night I was coming down the
slope of a mountain towards a narrow valley and river that were crossed
by an old, abandoned flume, of which nothing was now left but the
upright trestle-work and long horizontal string-piece. As the trail was
very difficult and the mule's pace was slow, I found myself dozing at
times, and at last I must have fallen asleep. I think I must have been
awakened by a singular regularity in the movement of the mule--or else
it was the monotony of step that had put me to sleep and the cessation
of it awakened me. You see, at first I was not certain that I wasn't
really dreaming. For the trail seemed to have disappeared; the wall of
rock on one side had vanished also, and there appeared to be nothing
ahead of me but the opposite hillside."

Uncle Sylvester stopped to look out of the window at a passing carriage.
Then he went on. "The moon came out, and I saw what had happened. The
mule, either of her own free will, or obeying some movement I had given
the reins in my sleep, had swerved from the trail, got on top of
the flume, and was actually walking across the valley on the narrow
string-piece, a foot wide, half a mile long, and sixty feet from the
ground. I knew," he continued, examining his napkin thoughtfully, "that
she was perfectly surefooted, and that if I kept quiet she could make
the passage, but I suddenly remembered that midway there was a break and
gap of twenty feet in the continuous line, and that the string-piece was
too narrow to allow her to turn round and retrace her steps."