The soul belongs to the psychic world. Doubtless there is on the Earth an innumerable quantity of souls, still heavy and coarse, barely freed from matter, and incapable of conceiving intellectual realities. But there are others who live in study, in contemplation, in the culture of the psychic or spiritual world. Those cannot remain imprisoned on the Earth, and their destiny is to live the Uranian life. The Uranian soul, even during its terrestrial incarnations, lives in the world of the absolute and divine. It knows that, though dwelling on the Earth, it is really in heaven, and that our planet is a star of heaven. What is the inner nature of the soul? What are its ways of manifestation? When does its memory become permanent, and maintain with certainty a conscious identity? Under what variety of forms and substances can it live? What extent of space can it overcome? What is the order of intellectual relationship which exists among the different planets of the same system? What is the germinating force which sows the world with seed? When can we put ourselves in communication with the neighboring earths? When shall we penetrate the profound secret of destiny? Mystery and ignorance to-day. _But the unknown of yesterday is the truth of to-morrow._ [Illustration] It is an historic and scientific fact, and absolutely incontestable, that in all ages, among all peoples, and under the most diverse religious manifestations, the idea of immortality rests invulnerable at the base of human consciousness. Education has given it a thousand forms, but did not invent it. It exists of itself. Every human being coming into the world brings with him, under a form more or less vague, this inner feeling, this desire, this hope. [Illustration] II. ITER EXTATICUM CŒLESTE. The hours and days that I devoted to the study of these psychological and telepathical questions did not prevent my observing Mars through the telescope, and taking geographical drawings of it, every time that our atmosphere, so often cloudy, would permit. Besides, it may be realized that while in the study of Nature and in science all questions are related to each other, yet that astronomy and psychology are most closely united to each other, since the psychic universe has the material world for its habitat, while astronomy has for its object the study of the regions of eternal life, and we could form no idea of these regions if we did not know them astronomically. In fact, whether we know it or not, we are living now, at this moment, in heavenly regions, and all beings, whatever they may be, are eternally citizens of heaven. It was not without a secret divination of things that antiquity made Urania the Muse of all the sciences. My mind had been occupied with the planet Mars for a long time, when one day, in a solitary ramble on the edge of a wood, after several hours of July heat, I seated myself at the foot of a clump of oak-trees, and was not long in dropping off to sleep.