The conclusions of this discourse are based entirely on this principle, my dear Quærens. I have endeavoured to show you that the physical law of the _successive transmission of Light_ in space, is one of the _fundamental elements of the conditions of eternal life_. According to this law every event is imperishable, and the past is always present. The image of the Earth as it was 6000 years ago, is actually now in space at the distance that light crossed it 6000 years since. The worlds situated in that region see the Earth of that epoch. We could see again our own direct existence and our different anterior existences. All that we need for this is to be at the proper distance from the worlds in which we had lived. There are stars which you see from the Earth, and which no longer exist, because they became extinct after they had emitted the luminous ray which has only just reached you. In the same way you might hear the voice of a man at a distance, who might be dead before the moment at which you heard him, if, perchance, he had been struck with apoplexy immediately after he had uttered his last cry. [Sidenote: There are living forms unknown to Earth.] I am very much pleased that this last sketch has enabled me at the same time to trace for you a picture of the diversities of existence and of the _possibility of living forms unknown to the Earth_. Here also you see the revelations of Urania are grander and more profound than those of all her sisters. _The Earth is only an atom in the universe._ I must pause here, for all these numerous and diverse applications of the laws of light are not apparent to you. On the Earth, in this dark cavern, as Plato appropriately termed it, you vegetate in ignorance of the gigantic forces in action in the universe. The day will come when physical science will discover in light the principle of every movement and the inner reason of things. Already within the last few years spectrum analysis has demonstrated to you that by the examination of a luminous ray from the Sun, or from a Star, you can learn what substances constitute that Sun and that Star. Already you can determine, across a distance of millions and millions of miles, the nature of celestial bodies from which a ray of light has come to you! And the study of light will afford still more splendid results, both in experimental science, and in its application to the philosophy of the universe. [Sidenote: Anticipations.]