Sometimes the whole tract swung to one side, like the tail of a live serpent; sometimes, for a glimpse, it would all disappear and then boil up again. What it was I had no guess, which for the time increased my fear of it; but I now know it must have been the roost or tide race, which had carried me away so fast and tumbled me about so cruelly, and at last, as if tired of that play, had flung out me and the spare yard upon its landward margin.