The first idea as to how the Moon was made is that a smaller core was formed in the gaseous matter of the Earth and that this core and the core of the Earth, which were at first joined together like a dumbbell, as shown in Fig. 101, began to spread apart like a pair of balls fastened together with a piece of elastic when they are whirled rapidly round each other, as shown in Fig. 102. [Illustration: FIG. 102.—BALLS CONNECTED WITH AN ELASTIC.] So, too, the high speed with which the Earth turned on its axis when it was in the making caused the smaller part to slowly move away and it became the Moon. The second idea is like the first, except that the Earth is thought to have cooled down until it was a melted mass, and it was then that a great upheaval took place in which a part, one-eightieth as large as that of the world itself, was torn out of its side and, whirling away by centrifugal force, the Moon was born. To throw off such a mighty part of its bulk as the Moon, it has been figured out that the Earth must have made a complete turn on its axis every 2 hours, instead of one turn in 24 hours, as it now does; and it was while the Earth was turning at this terrific rate of speed that the centrifugal force overcame the force of gravitation and tore the Moon from the Earth’s side and formed a little world of its own. [Illustration: FIG. 103.—MAP SHOWING PACIFIC OCEAN.] It is believed by some astronomers that the Moon was once that part of the Earth which is now filled up by the waters of the Pacific Ocean and there are several reasons why this seems very likely. First, if the waters which form the Pacific Ocean were rolled into a big ball it would be just about the size of the Moon; second, the space between the coasts of North and South America on the east, and Asia and Australia on the west, will be seen by referring to Fig. 103 to be roughly circular in form; third, there is a marked likeness between the volcanoes in California, in the Hawaiian Islands and in Japan to those on the Moon. [Illustration: FIG. 104.—IMITATING THE VOLCANOES IN THE MOON.] It was, doubtless, at this long ago time that the great volcanoes of the Moon, as well as those of the coasts of and on the islands in the Pacific Ocean were made, but what caused them can only be guessed at. There are two ideas, also, to account for them; one is that the pent-up gases inside the Earth and the Moon exploded and so threw up the volcanoes; the other idea is that showers of gigantic melted masses fell on the surface of both the Earth and Moon and so caused them. An experiment to show how the volcanoes might have been formed by showers of meteors can be made by covering the surface of your starboard with a layer of soft clay about 4 inches thick, and then throwing clay balls against it. Artificial volcanoes with craters and all will result. Compare your artificial volcanoes with Fig. 105, showing the real volcanoes on the Moon, and you will see they are quite alike.