“The surface of our planet is very rough, but still the grading for roads is light, as it is possible to ascend grades of 100 per cent or even steeper. Level grades on our roads are always avoided, and in districts where this cannot be done, we use electric roads.
“The cars are so constructed that different parts are electrically insulated from each other, by which means a part of the car can be placed under the influence of attraction and the rest under that of repulsion. This is done on down grades. The weight of the load and of part of the car pulling down and the weight of the rest of the car holding back. It is always arranged to have the car heavier than its load, and the driver can regulate the force used by balancing one against the other, so that a car of many tons shall press on the rails with the weight of only a very few pounds. Thus the wear and tear on road beds and rails is almost nothing and the roads are practically everlasting.”
“I am amazed,” said I, “to learn that the moon is inhabited and by a race apparently more advanced than our own. Our astronomers have assured us that the moon is a desolate played out barren world without air or water; totally unfit for inhabitants.”
“The astronomers could only report what they could see, and the side of the moon visible from the earth is as they describe it, but they have never seen the further side and never will, for that side is always turned from the earth. But the population of the moon is not far from half that of the earth and the people live in greater comfort. But there is no population living on the surface on the hemisphere facing the earth—I see this puzzles you,” he said.
It certainly did. “Do you mean that the Lunarians live under ground?” I inquired.
“I will explain. The moon is a much lighter body than the earth bulk for bulk, a cubic yard of it containing on an average only six tenths as much matter as an average yard of earth. The reason of this is that a very large part of the moon’s bulk is made up of interstices, caves and openings. Now it is a remarkable fact that the hemisphere of the moon facing the earth is much lighter than the further one, so much so that the center of gravity is 33 miles further from this side of the moon than from the further side. This fact has been suspected by some of your astronomers. The consequence of it is that the sea has all gone to the further hemisphere, and the near hemisphere is in the highest place, about 33 miles above the level of the sea. It is much as if a concave cap, the material of which is 33 miles thick at the center and tapers to zero all round the rim, were fitted on to a sphere. This rim is at the edge of the moon, as seen from the earth. Our atmosphere like yours, gets lighter as we ascend and is too thin to support life at a height of five miles, so that the great plateaus of our hither hemisphere are over 20 miles higher than any appreciable atmosphere. So you can see the impossibility of life on the hither surface of the moon if you reflect a moment what the conditions would be on a mundane plateau 33 miles above the sea level. Your highest mountains are only between five and six miles high, and you know the impossibility of either vegetable or animal life at even that altitude.