The sun slowly nears his setting, and sinks behind the opposite range. How we shiver! The last ray of sunlight has gone and already the ground is pouring out its heat into space, unchecked by the presence of air or clouds. The change takes place with marvelous quickness. A deadly chill creeps over all around. A whole fortnight of earth-time must pass before the sun’s rays will again touch this spot. Verily the contrasts of climate in the moon, during the twelve long days and nights which make up her year, are startling to human notions. But though the sun is gone we are not in darkness. The stars shine with dazzling brightness, and the huge body of the earth, always seeming to hang motionless at one fixed point in the sky, gives brilliant light, though at present only half her face is lit up and half is in shadow. Still her shape is plainly to be seen, for she has ever round her a ring of light, caused by the gathered shining of stars as they pass behind her thick atmosphere. She covers a space on the sky more than a dozen times as large as that covered by the full moon in our sky. [Illustration: THE EARTH AS SEEN FROM THE MOON.] It would be worth while to stay here and watch the half-earth grow into magnificent full-earth. But the cold is becoming fearful--too intense for even the imagination to endure longer. What must be the state of things on the other side of the moon, where there is no bright earth-light to take the place of the sun’s shining, during the long two weeks’ night of awful chill and darkness? It seems probable that a building on the moon would remain for century after century just as it was left by the builders. There need be no glass in the windows, for there is no wind and no rain to keep out. There need not be fireplaces in the rooms, for fuel can not burn without air. Dwellers in a city in the moon would find that no dust can rise, no odors be perceived, no sounds be heard. Man is a creature adapted for life in circumstances which are very narrowly limited. A few degrees of temperature, more or less; a slight variation in the composition of air, the precise suitability of food, make all the difference between health and sickness, between life and death. Looking beyond the moon, into the length and breadth of the universe, we find countless celestial globes, with every conceivable variety of temperature and of constitution. Amid this vast number of worlds with which space teems, are there any inhabited by living beings? To this great question science can make no response save this: We can not tell. Time for us to wend our way homewards from this desolate hundred-fold arctic scene. We have more to learn by and by about our friend and companion. For the present--enough. CHAPTER VII. VISITORS. We come next to the very largest members of our Solar System.