"But you must not utterly despair. Progress bears you on in spite of yourselves. One of these days, too, you will realize that you are citizens of the sky; then you will live in the light, in knowledge, in the mind's true world." While the inhabitant of Mars was teaching me the principal characteristics of his new country, the terrestrial globe had turned towards the east, the horizon had sunk lower, and the Moon had gradually risen in the sky, which she was illuminating with her radiance. Suddenly chancing to lower my eyes to where Spero sat, I could not repress a start of surprise. The moonlight was streaming over him as it did over me, and yet, although my body cast a shadow on the parapet, his figure was shadowless. I arose abruptly to assure myself of this fact. I turned about at once and stretched out my hand to touch his shoulder, watching the shadow of my gesture on the parapet. But my visitor had instantly disappeared. I was absolutely alone on the silent tower. My very dark shadow was thrown out sharply on the parapet. The Moon was brilliant, the village was sleeping at my feet. The air was mild and very still. And yet I thought I heard footsteps. I listened, and indeed did hear rather heavy footsteps coming towards me. Some one was evidently climbing the tower-stairs. "Monsieur has not gone down yet?" said the custodian, coming up to the top. "I was waiting to lock the doors, and thought the experiments must be over." [Illustration] [Illustration] IV. THE FIXED POINT IN THE UNIVERSE. The memory of Urania and the celestial journey on which she had borne me away, the truths she had made me realize, Spero's history, his trials in his pursuit of the absolute, his apparition, his story of another world, still haunted me, and kept the same problems (partly solved, partly veiled in the uncertainty of our knowledge) incessantly before my mind. I felt that I had gradually risen to a perception of the truth, and that the visible universe was really but an appearance, which we must pass through in order to reach reality. The testimony of our senses is but an illusion. The Earth is not what it seems to be. Nature is not what we think. In the physical universe itself, where is the fixed point upon which material creation is in equilibrium? The natural and direct impression given by the observation of Nature is that we inhabit a solid, stable Earth, fixed in the centre of the universe. It took long centuries of study and a great deal of boldness to free ourselves from that natural conviction, and to realize that the world we are on is isolated in space, without any support whatever, in rapid motion on itself and around the Sun. But to the ages before scientific analysis, to primitive peoples, and even to-day to three quarters of the human race, our feet are resting on a solid Earth which is fixed at the base of the universe, and whose foundations are supposed to extend into the depths of the infinite.