"Well, for example, warm winds and warm ocean currents coming from the north and encountered and reported by practically all arctic explorers; the presence of the limbs and branches of trees with green foliage upon them floating southward from the far north, far above the latitude where any such trees are found upon the outer crust; then there is the phenomenon of the northern lights, which in the light of David Innes' theory may easily be explained as rays of light from the central sun of the inner world, breaking occasionally through the fog and cloud banks above the polar opening. Again there is the pollen, which often thickly covers the snow and ice in portions of the polar regions. This pollen could not come from elsewhere than the inner world. And in addition to all this is the insistence of the far northern tribes of Eskimos that their forefathers came from a country to the north." "Did not Amundson and Ellsworth in the Norge expedition definitely disprove the theory of a north polar opening in the earth's crust, and have not airplane flights been made over a considerable portion of the hitherto unexplored regions near the pole?" demanded the ape-man. "The answer to that is that the polar opening is so large that a ship, a dirigible or an airplane could dip down over the edge into it a short distance and return without ever being aware of the fact, but the most tenable theory is that in most instances explorers have merely followed around the outer rim of the orifice, which would largely explain the peculiar and mystifying action of compasses and other scientific instruments at points near the so-called north pole--matters which have greatly puzzled all arctic explorers." "You are convinced then that there is not only an inner world but that there is an entrance to it at the north pole?" asked Tarzan. "I am convinced that there is an inner world, but I am not convinced of the existence of a polar opening," replied Gridley. "I can only say that I believe there is sufficient evidence to warrant the organization of an expedition such as I have suggested." "Assuming that a polar opening into an inner world exists, by just what means do you purpose accomplishing the discovery and exploration of it?"