He who has witnessed a storm along a rocky coast-line, has marked the breakers battering against the weather-bleached cliffs, and heard the thunder-like rattle of the shingle at the recoil of every wave, needs not to be told how vast an amount of sediment must in this way be formed. The pebbles of the beach are ground down still smaller, the sand produced by their friction finds its way to a lower level, while the finer particles taken up by the water are borne out to sea, and if a current traverse the locality may be transported for leagues, till they at last settle to the bottom. The floor of the sea is consequently always receiving additions in the form of fine mud--the waste of the land--derived either from breaker-action, rivers, or icebergs, so that a series of marine deposits exactly similar to those we find among the rocks of our hills and valleys, must be constantly in the course of formation. If circumstances be favourable, the shingle of the beach may eventually either be covered over or reach a part of the sea undisturbed by currents or waves, and then consolidate into what we call conglomerate or pudding-stone. The sand, as before, becomes sandstone, and the mud laminated shale or hardened clay. These deposits may go on forming for thousands of years, until at last some slow elevation or some sudden upheaval of the ocean bed brings them to the light of day as part of a new continent. Thus exposed they would differ in no respect from rocks of a similar kind now visible, and the geologist, in tracing out their origin and history, would have no hesitation in ranking them among the ordinary marine formations of the globe.