His whistle sounded innocent enough, yet I mistrusted him, having caught his eye when he was looking at my bloody foot; and so I said as much to Elzevir, who only laughed, saying the boy was simple and harmless. But from where I sat I could peep out through the brambles in the open gap, and see without being seen--and there was my young gentleman walking carelessly enough, and whistling like any bird so long as Elzevir's head was above the wall; but when Elzevir sat down, the boy gave a careful look round, and seeing no one watching any more, dropped his whistling and made off as fast as heels would carry him. Then I knew that he had guessed who we were, and was off to warn the hue and cry; but before Elzevir was on his feet again, the boy was out of sight, over the hill-brow. 'Let us move on,' said Block; 'tis but a little distance now to go, and the heat is past already. We must have slept three hours or more, for thou art but a sorry watchman, John. 'Tis when the sentry sleeps that the enemy laughs, and for thee the Posse might have had us both like daylight owls.' With that he took me on his back and made off with a lusty stride, keeping as much as possible under the brow of the hill and in the shelter of the walls. We had slept longer than we thought, for the sun was westering fast, and though the rest had refreshed me, my leg had grown stiff, and hurt the more in dangling when we started again. Elzevir was still walking strongly, in spite of the heavy burden he carried, and in less than half an hour I knew, though I had never been there before, we were in the land of the old marble quarries at the back of Anvil Point. Although I knew little of these quarries, and certainly was in evil plight to take note of anything at that time, yet afterwards I learnt much about them. Out of such excavations comes that black Purbeck Marble which you see in old churches in our country, and I am told in other parts of England as well. And the way of making a marble quarry is to sink a tunnel, slanting very steeply down into the earth, like a well turned askew, till you reach fifty, seventy, or perhaps one hundred feet deep. Then from the bottom of this shaft there spread out narrow passages or tunnels, mostly six feet high, but sometimes only three or four, and in these the marble is dug. These quarries were made by men centuries ago, some say by the Romans themselves; and though some are still worked in other parts of Purbeck, those at the back of Anvil Point have been disused beyond the memory of man.