Symmes believed that after passing through an icy circle, as one neared the Pole, there existed an Open Polar Sea—a fairly common notion at the time—and that conditions actually became warmer the closer one approached the great openings he knew were there. In support of these ideas he ransacked all existing accounts of northern voyages and expeditions for proof, and found reports of animals apparently migrating northward—as depicted here as an illustration for an 1882 article in Harper’s New Monthly Magazine. Where were they going? Symmes was certain they were heading for the Polar opening, on their way to spend a cozy warm winter inside the Hollow Earth.