Scientific men believe that when our planet first went circling swiftly in its orbit it was a glowing, globular mass of fiery vapors; but as time passed, the icy chill of space slowly cooled these vapors, and chemical changes steadily modified, sorted, and solidified the materials into the beginnings of the present form and character, until at last _water_ came into existence. This must have been at first in the form of a thick envelop of heated vapors, impregnated with gases, that inwrapped the globe in a darkness lit only by its own fires. After that, when further changes had come about,—let us picture it,—what deluges of rain were poured out of and down through those murky clouds where thunders bellowed and lightnings warred! At first all the rains that fell must have been turned to steam again; but by and by the steady downpour cooled the shaping globe so that all the water was not vaporized, but some stayed as a liquid where it fell, and this increased in amount more and more, until finally, between the hissing core of the half-hardened planet and the dense clouds which kept out all the sunlight, there rolled the heated waves of the first ocean—an ocean broken only by the earliest ridges, like chains of islands, marking the skeletons of the continents that were to follow—an ocean sending up ceaseless volumes of steam to form new clouds. [Illustration: EATING AWAY THE COAST.] Yet all the while the cooling of the planet went on. Now, when any heated substance cools it contracts, and the globe as a whole is no exception to the rule; but a sphere formed of so incompressible a substance as rock can shrink only by some sort of folding or displacement of its surface. Therefore, as the cooling of our globe proceeded, explosions and swellings constantly occurred at weak points or lines on or near the surface, where the prodigious strain forced a break. That these upheavals were most prominent and extended in the northern hemisphere is shown by the fact that the great masses and heights of land are grouped there; and the trend of mountain-ranges seems to show that the range of breakage and upheaval was in general in north-and-south lines. Elsewhere, and mainly in the southern hemisphere, broad areas of perhaps stiffer crust sank downward, making the vast depressions into which poured the waters of the primeval sea, and where our oceans still sway and roll. [Illustration: SURF AT FORT DUMPLING, R. I.] All these changes, however, have been in the direction of insuring more and more stability; and when the ocean water had thoroughly cooled, the very chill of its vast masses in the depths of the troughs assisted in the work, for the cold water, by more rapidly withdrawing their heat, caused the rocks beneath their basins to become denser, thicker, stronger, and consequently less liable to break or change, than were those rocks forming the foundations of the continents.