To All the World: I declare the earth is hollow and habitable within; containing a number of solid, concentric spheres; one within the other, and that it is open at the poles twelve or sixteen degrees. --J. Cleves Symmes of Ohio, late Captain of Infantry, April 10, 1818; quoted in Sprague de Camp and Ley, Lands Beyond, New York, Rinehart, 1952, x