In 1818 US Army veteran John Cleeve Symmes proposed a theory that "the earth is hollow, with openings at the poles, and inhabited within; containing a number of concentric spheres, one within the other..." As part of a campaign of lectures, newspaper articles and open letters intended to win over the public and enlist congressional support for an expedition to the North Pole, Symmes published a pseudononymous account of a voyage to the interior world. Symzonia describes the expedition of one Captain Adam Seaborn, who sails into the interior via the northern polar opening and encounters an...