Near Mount Misery, where the castaways built their outpost, a few stalks of celery still sprout, and you can forage for scattered limpets like those the men survived on. And a short way inland, partially buried in an icy stream, are several rotted wooden planks that, hundreds of years ago, washed up onto the island. About five yards long and hammered with treenails, these boards are from the skeletal frame of an eighteenth-century hull—His Majesty’s Ship the Wager. Nothing else remains of the ferocious struggle that once took place there, or of the ravaging dreams of empires.