In 1818 John Ross led an expedition to search for the Northwest Passage. He got as far as Baffin Bay, but when he reached the only practicable entrance to the passage he declared it to be no more than a bay enclosed by mountains. In subsequent years he was widely derided for that error and carried the scars of public and professional humiliation for the rest of his life. In 1829 he mounted a private expedition to search for the passage, during which...