At low tide he walked over the sands to the headland and round the corner to the little bay facing the open sea. It was inaccessible by boat, because seams of rock jutted out and currents swirled round them treacherously. But you could walk there if you chose one of the lowest ebb tides that receded a very long way, you could not linger on the expedition, for once the tide was  the turn, it came in rapidly. For this reason very few people cared to explore the little bay fresh and unlettered, as it was completed covered by the sea at high tide. The cave looked mysteriously dark, cool and inviting, and he penetrated to the farthest corner where he discovered a wide crack, rather like a chimney. He peered up and thought he could sea a patch of daylight. It was not possible to ‘linger on the expedition’ because