"When we sailed into this harbor early this morning, my lanthorn suddenly began to swing so violently that it was bashing against the ceiling and spilling oil about the cabin," Enoch said. "And so I took it down and adjusted the chain to a different length, as you see it now." Enoch now lifted the lanthorn’s chain from its hook in the ceiling-beam, and began to feel his way along, link by link, until he came to one that was worn smooth. "This is how it was when we entered the harbor," he said, and then re-hung the lanthorn so that it dangled a few inches lower than before. He pulled it away to the side and then let it go, and it began swinging back and forth in the center of the cabin. "So it follows that the frequency we observe now—swing, swing, swing—is tuned to the natural period of this harbor’s waves."