Page:Popular Science Monthly Volume 51.djvu/846

828 hardened ooze again becomes the bottom of an ocean, subject to another rain of shells; and so the change goes on, and we may trace the rhizopods back to the Archæan time, millions of years ago, their story being told by the limestone deposits alternating between the metamorphic schists of that ancient period—monuments of the part these insignificant creatures have taken in preparing the world for man. The chalk cliffs of England are among the visible evidences of this work, the chalk being formed of rhizopods once deposited at the bottom of a sea, but now reared high above the surface to tell the marvelous story. The city of Paris is built of stone formed by rhizopods and other forms, and the pyramids of Egypt are constructed of the remains of various species of fossil animals; yet how these magnificent works of man pale into insignificance before the unconscious work of these minute animals!

Very near the rhizopods are the sponges; lowly creatures whose skeletons are of great value—their collection and preparation forming a vast industry in many parts of the world; a step higher in life we find the coral polyp, secreting lime and piling up reefs and islands that are important girders of the globe. I have spent days in following a coral reef in the Helderberg Mountains of New York far from the reefs of to-day; and we find evidences of them everywhere in the rocks of early geological times. The great reef of Australia, the populous coral keys of the equatorial Pacific, the State of Florida, a reef of seventy-eight thousand square miles in extent, illustrate the value of this polyp to man.

All these animals have other values. From the rhizopod cliffs of Dover comes chalk, while heat is supposed to have changed the skeletons of sponges into flint, so valuable in many ways. Heat has transposed the old coral reefs into beds of marble; and we have the Capitol at Washington, and all the noble works of art of the old Roman and Grecian masters, carved from the crystallized remains of these lowly creatures.

The shells of the seashore and river all have a direct value; the oyster industry of New York city alone represents a capital invested of over two million dollars, which means the support of thousands of men, women, and children. Even the discarded shells constitute an important branch of trade in themselves. Germany and England use tons of pearl oysters, sending them to us in the form of buttons, cheap ornaments, and other articles. The pearl fisheries of the Persian Gulf pay one million dollars per annum; of Australia, three hundred and eighty thousand dollars; while those of Lower California have produced some of the finest and most valuable pearls during the past two centuries. The collection of abalone shells in the State of California means an income of over fifty thousand dollars to the parties interested,