The ocean has been busily at work—in old times, inland; in later times, coastwise; in all times subterraneously. This last point is proved by the volcanoes, and that in a twofold argument. Such volcanoes as are now extinct, are so because they have lost all communication with the sea; such of them as are active, are so because they draw supplies of salt-water from the nearest part of the ocean, and this they can only do subterraneously. But in speaking of the labours of the ocean, I shall confine myself to the seashore, as the scope of this little volume does not go beyond that region. The point where sea and land meet is the critical point for all observers of Nature. Here the disciple of geology should serve his apprenticeship, and if he cannot accumulate facts, and glean a kind of inspiration here, he cannot do so anywhere. Moreover here, better, we think, than in any inland scenery, Man can muse and meditate. That ever-varying curved line of moisture on the shore depicts the fluctuating changes which momentarily visit his “little day;” the tide running in is the flood of his early life; the tide running out is the ebb of his declining years; the vast sweep of the coast, backed by the upland ranges and everlasting hills, and itself only lost to sight in the far horizon, tells of a steadfast future, an immutable eternity. Above all, those who desire to note epochs in the flight of Time, and to set up way-marks in the Earth’s chronology, must study the line of the sea-coast, the ancient and the modern, for here, if anywhere, the dial-plate is uncovered, and the shadow of the gnomon may be traced through some seconds of the enormous day which has witnessed the existence of the heavens and the earth. I have already, in my opening chapter, remarked how the sea brings down, in the course of ages, many a pebbly beach from cliff and causeway. But I am far from assuming, therefore, that _all_ the pebbles of a beach come from the land. The usual bottom of the sea is, indeed, no pebbly shore; but there are many submerged rocks of sandstone and oolite, out of whose ribs and crevices, from time to time, fossils may be washed, just as our own chalk-cliffs, the main resort of the siliceous pebbles, were themselves laid down in deep seas. And the salt water, which is always acting gradually to dissolve certain rocks, when it removes portions of these from the edges and promontories, will occasionally bring their contents to shore. But these results, although interesting to those who maybe searching after pebbles (and a deep-sea pebble is a prize), were not what I pointed at when I spoke of the labours of the ocean.