Again the strings across the path were broken. My heart beat heavily as I began to follow back towards the monument the track of the broken thread. It led right up to it, on the side away from the castle, and then stopped. The other threads all round the monument were intact. Having learned so much, my first act was to prevent discovery of my own plan. Accordingly I carefully removed all the threads, broken and unbroken. Then I began to make minute investigation of the monument itself. As it was evident that whoever had broken the threads had come straight from it, there was a presumption that there was an opening somewhere. The rock below was unbroken and the stonework was seemingly fixed on the rock itself. By a process of exclusions I came to the belief that possibly the monument itself might be moveable. Accordingly I began to experiment. I pressed against it, this way and that. I tried to move it by exercising pressure top and bottom in turn; but always without avail. Then I began to try to move it sideways as though it might be on a pivot. At first there was no yielding, no answer of any kind to my effort; but suddenly I thought I perceived a slight movement. I tried again and again, using my strength in the same way; but with no result. Then I tried turning it in the suspected direction, holding both my hands low down on the corners of the boulder; then going gradually up higher I pursued the same effort; again no response. Still I felt I was on the track and began to make efforts in eccentric ways. All at once, whilst I was pressing with my left hand low down whilst I pulled with my right high up on the other edge, the whole great stone began to move in a slow easy way, as though in perfect poise. I continued the movement and the stone turned lazily over on one side, revealing at my very feet a dark opening of oval form some three feet across its widest part. Somehow I was not altogether surprised; my head kept cool in what was to me a wonderful way. With an impulse which was based on safety, lest the opening of the hole should make discovery of my presence, I reversed the action; and the stone rolled slowly over to its old position. Several times I moved it from its place and then back again, so that I might become accustomed to its use.