It must also, in marking out this theory, be admitted that as the center of the Earth is approached this opening must be somewhat enlarged, and must assume a concave shape from the center; such being the case, the diameter must increase from one thousand to two thousand miles or more, which is very likely to be the fact. With the motion or revolution of the Earth, the water would assume this condition on principle of the swinging of a pail of water over the head, and would merely be a placid ocean as boundless to the eye as the waters on the surface. In these expanses of water, it is quite reasonable to presume that islands and large bodies of land may exist the same as outside, and that many fossil specimens thought to have existed on the outer surface in an early antiquity may have originated in the center of the Earth and may even still exist; their ancient skeletons having been thrown to the Earth’s surface by the centrifugal forces of water in the same way that all the different stratas of rock have been cast up and mixed in one grand conglomeration from the Earth’s center to its circumference. These facts seem clearly to prove by these migratory birds and animals: First an open sea; second it must be fresh water or mostly so; third, it must produce or contain desirable food elements different from what exist in the ocean on the outside, on which these birds can live when they reach their breeding grounds from which they are reported to return with largely augmented numbers. Now this consistent query can arise: Do they stop at a near point after passing this great boundary line of ice and find suitable and pleasant feeding grounds, or go on 500 or 1,000 miles farther? At that distance, the water is more likely to be modified in temperature and better adapted to their tastes and comfort. It seems quite right to assume that they come to inland seas, and pleasant bays, and sounds supplied with food from their shores and feeding grounds, rather than being supplied with anything existing on external parts of the Earth; otherwise, their supply must all be drawn under the ice belt or pass through this great Arctic filter. Again this thought comes up. How did these birds get sight of or learn of this internal feeding, and probably breeding ground? As migratory birds usually fly at great height, they would have an advantage over man in seeing this open ocean, as it is reasonable to think they may have bred as well as fed there. It is only a natural sequence of their migration in and out of this belt or ice circle, just as we recognize their flight north and south with the season’s changes.