In the illustration at the head of this chapter the large ring represents the earth as a vast ball of hot vapor. The very small ring in the centre shows the present size of the globe as compared with its first expansion. The circle marked 1 shows the earth as a simple sphere of vapor, its earliest condition. The circle 2 shows us the stage where, by the force of gravity, and the cooling resulting from the radiation of heat, the sphere of gas began to have a fluid centre, or core. We must understand that the condensing particles in the centre were not rendered solid, but fluid, as you may see the molten glass or iron at a glass-works or iron-foundry. This fluid state probably still continues at the centre of the earth. Figure 3 shows us the condensation going on. As the globe cools, a solid crust, marked _x_, is formed around the fluid centre, and between the centre and the crust the matter of the globe is hardening, while the outer envelope beyond the crust is still gas. Figure 4 shows another change. The vapor has cooled and condensed in space, and has fallen back upon the globe in rain and snow. These rains corrode and wash the surface of the crust, and finally by their excess cover the whole crust of the earth with an ocean, marked _o_. Thus the liquid centre and the solid crust are wrapped in a mantle of water. This universal ocean is not cold and clear as are the oceans of to-day. The intense heat of the globe has made these waters boil and send off dense clouds of steam, and thus the water-wrapped world is further enveloped in a veil of mist. Would it then have been hidden from our sight if we had been Afrites, watching it as we sat on some far-off planet? No; we should have seen it still, grown smaller and paler perhaps, but the mist-veil would have caught and reflected the sunlight, as the clouds do at sunset. This was the reign of the waters upon the surface of the globe, while the central fires were burning and rolling in the abyss beneath the waters and the hardened earth-crust. When we say fires, of this interior heat, we must not think of flames, but rather of such heat as that of molten metal in a furnace. The universal ocean that wrapped the world at this time was full of salt and earthy matter and was turbid, as a river in flood time. From the deposit of this matter upon the earth-crust, rock strata or layers were formed. Figure 5 shows us still another stage of earth-building. The reign of the waters is disputed by the long-imprisoned heat. This heat exerts its force, and tugs and lifts at the earth-crust until it bulges and cracks and rises up, or, as we say, is elevated. Earthquakes and volcanoes alternately depress or upheave a part of the earth’s surface. Great depressions are formed, into which the waters gather, while the thick earth-crust is tilted up into mountain chains, marked _z_, which are reared above the waters. These wrinkling folds of the crust are the world’s first dry land.[2]