828 POPULAR SCIENCE MONTHLY. 



hardened ooze again becomes tlie 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 Archtean time, millions of years 

 ago, their story being told by the limestone deposits alternating 

 between the metamorphic schists of that ancient period monu- 

 ments of the part these insignificant creatures have taken in pre- 

 paring 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 ! 



A^ery near the rhizopods are the sponges; lowly creatures 

 whose skeletons are of great value their collection and prepara- 

 tion 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 Moun- 

 tains of New York far from the reefs of to-day ; and we find evi- 

 dences of them everywhere in the rocks of early geological times. 

 The great reef of Australia, the populous coral keys of the equa- 

 torial 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 crystal- 

 lized 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. 



