"April 21. There is on the planet Mars a subterranean passage through it from pole to pole, which Mr. Swedenborg informs me he has thoroughly explored. There is more truth than poetry in what is known as Symmes' hole as applied to your earth. When the time comes by the settlement of your as yet vast millions of uninhabited acres, and a change takes place in northern temperature and conditions, the people of that day will discover within and through the very heart center of your earth a country nearly a third as large as the exterior surface, and by that time every thing therein will be sufficiently progressed and developed to supply the wants and invite the ambition and energies of the people of that period. But this discovery, or rather the occupation of this subterranean country, is very far off in point of time, and the human race of earth will then be quite different from what it is now. They will have so changed by the lapse of time and the law of progress as to be enabled to pass into the new country by way of the north pole with ease and safety. The north pole is the true opening, and can not be reached until the fullness of time, as I have indicated. As the area of territory of Mar's surface was about being densely covered by population, and apprehensions were being entertained for the future of the race, lo and behold, the new interior country was discovered and subsequently peopled. By the time it is crowded no more will be needed, for the planet by that time will have passed into its spiritual orbit and into the ocean of spiritual ether, where suffering can never come from lack of room. This will be the future history of your planet, and you will pass through the same experiences and reach the same ultimate. Behold how infinitely wise all things are forearranged. Just as we need by our development new limits, new appliances and new things, they are ready for our use, and are never disclosed until we are ready for and need them.