“Here the age of the moon has increased to nearly seventeen and a half days. The sunset line has advanced to the borders of the _Mare Nectaris_ and the _Mare Tranquillitatis_. Toward the south a vast region which was very brilliant in the morning and midday light with the reflections from mountain slopes and the rays of Tycho, has passed under the curtain of night. The great crater rings on the eastern border of the _Mare Nectaris_, and thence upward to the South Pole, are beginning to reappear, but with the shadows of their walls thrown in a direction opposite to that which they assumed before. By a little close inspection you will recognize Theophilus and its neighbors which were so conspicuous for many days while the sunrise was advancing, but which have been almost concealed in the universal glare of the perpendicular sunshine since the Full Moon phase was approached. On the _Mare Tranquillitatis_ and the _Mare Serenitatis_ it is late afternoon, and your favorite ‘Marsh of a Dream’ has become a true dreamland.” “This oncoming of night,” said my friend, “seems to me more imposing, and more suggestive of mystery than was the advance of day.” “Surely it is. Do we not experience similar sensations when night silently creeps over the earth? But it imparts a feeling of loneliness and desolation when we watch it swallowing up the barren mountains and plains of the lunar world that we do not experience in terrestrial life. There are no cheerful interiors on the moon to which one can retreat when darkness hides the landscapes. There is another thing about the lunar night to which I have made but scant reference thus far. I mean it’s more than Arctic chill. Imagine yourself standing there in the midst of the broad plain of the _Mare Tranquillitatis_. Toward the east you would see the sun close to the horizon, yet blazing bright and hot, without clouds or mists to temper its rays. The rocks or soil beneath your feet would perhaps be cold to the touch, because the surface of the moon radiates away the heat very quickly, but your face and hands would be almost scorched by the intense solar beams. Looking toward the west you would see the shining tips of mountains suddenly extinguished, one after another, and when the sharply defined edge of the advancing night passed over you it would be as if you had plunged into a cold bath. In a little while, if you remained motionless, you would be frozen. No clothing would suffice to keep you warm. Nothing that polar explorers have ever experienced can be likened to the cold of the lunar night. Only the apparatus of the laboratories for producing temperatures, capable, when combined with pressure, of liquifying and solidifying the air itself, can bring about upon the earth a lowering of temperature comparable with that which occurs during the lunar night.” “But I do not exactly see why night should be so much colder on the moon than on the earth. She is not farther from the sun.”