So we find in this large aquarium, the great sea, the same processes going on—the same material manufactured that took place in what is termed the older geological formation. Can we say that creation is complete? That the earth is finished, and, like a ship we read about the other day, to be disposed of for the old iron it contains? Not long since I visited a marble quarry, from which very curious and beautiful marble, resembling the onyx, was being taken. There were thick strata cropping out; and the air, and rain, and frost had disintegrated the exposed parts, so they looked as old as the earth. But just beneath, and in various places, were little springs of warm water, and as these bubbled out of the earth they deposited on cooling and exposure to the air, the same kind of marble—and there I saw going on the process of marble making that had continued doubtless for thousands of years. On the shores, in the tide, pools and lagoons of Monterey bay we often gather little plants classed with the _Algæ_, or sea-moss, which we call diatoms. They are exceedingly small—some of them—so that we have to magnify them with the microscope several hundred diameters, in order to see how they are formed. Some kinds grow on the larger sea weeds, some on the rocks, and some appear to be free in the water, coming ashore in large quantities with the foam of the surf, and giving a greenish brown color to the sand of the shore. These diatoms are composed mainly of silex—flint. If we examine the rocks of our highest ridges and mountains and the cliffs of our shores in places, with the microscope, we shall find them largely composed of fragments of diatoms and spiculæ of sponges. And these are chiefly of the same species that we find alive to-day. Thus while the “chalk rocks” on our shores, the sand stones and harder rocks are melting away under the pounding waves of the sea, and being carried to the lower bottoms, fresh supplies of diatoms and sponges are mixed therewith, and we have a continuation, under our eyes, of what was begun thousands of years ago.