I surveyed it for a moment, and felt just the least apprehension; but taking a grip on my nerve I bound the hook firmly to the rope and slung it up over the wall, then pulled in to see if it had gripped. It wasn't an easy matter to throw at all in such a position, and the first attempt was unsuccessful; but at the third throw the rope held. It was difficult to test it properly by taking the strain, for I was obliged to cling with one hand to the slates, and if I tugged at the rope and it came away suddenly I should probably lose my grip and be sent over the edge. However, I jerked it three or four times, and it seemed firm enough; then summoning my courage I took the rope in both hands, pulled myself slowly up along the slanting slates, and was soon at the foot of the wall. Before ascending I again jerked at the rope to test it for the last time, and feeling reassured began climbing up hand over hand. But I had scarcely mounted a couple of feet before I felt something give, and for a dizzying moment I hung in mid air expecting to fall, and gazing frenziedly for some possible crevice in the roof beneath me to catch my fingers in if the rope should slip. But it seemed to be steady enough now, and cautiously I recommenced the ascent. I was half-way up, when again there came that sickening jerk as though something were breaking loose; but knowing now that my only chance was to reach the top of the wall, for if I fell it would be with too great a force to stay myself, I scrambled on with desperate speed, the rope seeming to slip with every heave upward of my body. And it was just as I reached the top, the fingers of one hand clutching at the stone, that the rope came away in the other hand, while I swung perilously, gripping at the wall with the bare tips of my fingers. But with a leap upward I caught at the top with my free hand, though I had to drop my rope to do so, and was soon safe astride the barrier looking down on the other side. If I had been met by a blank roof I should have been in a perilous predicament indeed, perched up there, with no rope to descend by. But my gamble with fortune proved a lucky one, for enclosed within the walls of the stack, and only a few feet below me, was the window I had hoped to find; or skylight rather, for such it was, like a shallow dome looking up at me with a great round eye.