So with the seasons with all that they mean in the life of the world; spring never fails to follow winter. Little things happen that make spring "late," as we say; but spring itself never fails to come and always in its right place in the procession of the year. All this because the earth stays in its orbit and spins on its axis. Watches break their mainsprings, clocks run down. These things "happen"; but we never think of saying that the mainspring or the wheels "happened," or that they "happened" into their places in the watch. The worlds not only make their appointed round as regularly as the wheels of a watch but they never run down, and the power that keeps them going and in their places never breaks. If it ever occurred in any other way--if we should hear of a world flying out of its orbit and going banging around among the other worlds, we could talk of "happening." NATURE'S ACCIDENT INSURANCE SYSTEM We might call these laws that make it so certain that nature's business will go on as usual, rain or shine, the Accident Insurance of the Universe. We have nothing quite like it in human insurance systems; for these only make it up to you--the best they can--after some accident has happened. Nature's insurance system, on the other hand, makes it certain that nothing _will_ happen to change the main course of things. The protective insurance of the universe is woven right through Nature itself. The continents, for example, were bound, in due course, to rise in their places, because it is the nature of cooling masses to shrink and for the outside to cool the faster and to harden and to wrinkle up. It doesn't matter whether the cooling mass is a little baked apple or a big hot earth. [Illustration: THE CLOCK OF THE AGES By representing the great geologic periods of time in the form of a clock-face a writer in the _Scientific American_ enables us to form a rough conception of their duration, their distinguishing features, and their relations to one another, according to ideas associated with the theory of La Place, but which have been considerably modified in the light of later reasoning and investigation. The view now generally accepted, for example, is that the Azoic era was longer than all subsequent time. But, taking the picture as it stands, each "hour" represents 3,000,000 years. For a quarter of the total period up to the very recent appearance of man "there was darkness upon the face of the deep." Next after the Azoic was the Laurentian Period, when "the dry land appeared." Later came the dawn of life, and this life, like the inanimate matter which preceded it, kept rising and continues to rise, as the ages pass, to higher, more beautiful, and nobler forms. ]