CORAL REEFS AND CAVES IN THE PACIFIC.

THE ISLANDS OF THE PACIFIC-HOW THEY HAVE BEEN FORMED-WHAT THE CORAL IS-THE WONDROUS ARCHITECTS OF THE SEA-WHAT A UNITED STATES STEAMER SAW-HOW THE CORAL IS FISHED FOR-ROMANTIC STORY OF A CAVERN-HOW IT WAS DISCOVERED-AN ELOPEMENT AND EXERCISE IN DIVING-LOVE AND TURTLES-A BATTLE IN THE WATER-KILLED by SHARKS-A MAIDEN'S GRIEF-THE PERIL OF A LOVER-SURPRISING A FATHER-IN-LAW-END OF A SUBMARINE COURTSHIP.

The waters of the Pacific ocean contain thousands of islands far away from the coast. Their presence is recognized, long before they become visible, by clouds directly above them in the otherwise clear sky. The land absorbs the heat of the sun, and accumulates it faster than the water; soon an ascending current of warm air is formed, carrying up moisture into the colder regions of the atmosphere, where it is condensed and forms clouds. A similar phenomenon is observed in our western plains, where the sky is frequently clear enough in the morning, but by ten or eleven o'clock, enough heat has been accumulated to cause the formation of clouds.

The islands of the Pacific are of two kinds, called the higher and the lower. The lower rise but seven, ten, and rarely as high as one hundred feet above the level of the sea; while the higher islands reach an elevation of 10,000, 12,000, and even 15,000 feet. There is no transition between them. The most remarkable are the lower islands. Their appearance is very peculiar. In the first place, the eye is arrested by a white beach; then comes a line of verdure, due to tropical trees; then a lagoon of quiet water, of a whitish or a yellowish color, then another line of verdure, and finally, beyond all, the dark, blue waves of the ocean. Whitsuntide Island is a remarkable model of the structure of these islands:

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It is a ring rising seven or eight feet above the sea level, enclosing a lagoon, and presenting the characteristics just described. The lagoon inside is but a few fathoms deep; but on the outside of the island, the water is fifteen thousand feet deep. Here, then, we evidently have a tower-like structure reaching up from the bottom of the sea, and having a depression in its summit. Some of these lower islands are fifty miles across, but most of them are not so large. In some the ring is broken at several points, and these are designated by the Malay word atoll.

The island of Tahiti, the principal one of the Society Islands is a good example of the second class or higher islands. It rises seven thousand to eight thousand feet above the level of the sea, has no lagoon in its center, but a crater, and the water around it is very deep. It may, in fact, be considered as a mountain rising to a height of some eighteen thousand feet from the bottom of the sea. Outside of it is a double girdle of low islands, one near, which Darwin calls a fringing reef, and one further out, to which he gives the name of a barrier reef.

On examining these reefs, and the lower islands, their structure will be found made up entirely of animal remains, generation after generation having left their homes, consisting of limestone, to accumulate there. On the top, we find these animals living and growing, in all colors, shapes, and sizes. The highest islands, on the contrary, except those near the continent, like Borneo, Sumatra, etc., are entirely volcanic, and do not contain sandstone, granite, or gneiss, like the mountains of the continent.

The limestone of the lower islands is not due to sedimental deposits from the ocean, but is the work of the coral animal, the great architect of the sea.

The great savant, Prof. Agassiz, describes them as follows: "These animals are but a sac, like the finger of a glove, only more leathery. Around the mouth is a series of tentacles, formed by a prolongation of the skin. They are all skin, in fact, and have no special organs, yet they digest food with

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tremendous rapidity, absorbing it directly. It makes no difference if you turn them inside out; they will digest just as well as before. You cannot kill them by dividing them; for they live all over, like a plant. For this reason they have been called zoophytes.* If you cut one into eight parts, each part will live and set up in business for itself. Like all other animals, however, they grow out of eggs. The eggs are formed within the skin, which is double, and divided into cells by partitions or septa. When mature, they detach themselves, Inove about in the water until they find a favorable place, and then establish a new colony. They do not contribute to the growth of their parent colony, which is effected in another. way.

"On examining a piece of coral, it is seen to be full of little holes, popularly supposed to be the places for the stomachs of the animals, but this is not so, at all; the coral animal does not form a secretion around it like the mollusks,† but inside, between the two folds of its skin. Coral is, therefore, the bones and not the skull of the animal. As before stated, these animals work in societies or colonies, and their tendency is to repeat the forms peculiar to each species; thus we have corals shaped like a hand, like the branches of trees, like mushrooms, like a brain, with its convolutions. They grow and multiply in these societies by budding or gemmation. The side of the animal begins to bulge out, and the protuberance so formed develops into a new mouth, which soon cats and digests for itself, but does not separate from its parent. This process goes on symmetrically, and produces the variety of regular shapes just described.

"Some distance below the surface, we no longer find these beautiful shapes, but a dense, solid, coral rock. Take for instance, the coral reefs of Florida. Beginning one hundred

*The term Zoophyte is applied to simple polyps and compound individuals consisting of many polyps united together, as in most corals. They often branch like vegetation, and the polyps resemble flowers in form.

† Mollusks are invertebrate animals, having a soft, fleshy body, which is inarticulate, and not radiate internally.

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and twenty feet below the surface, we first find about thirty feet of massive rock, then the astræa,* then the meandrina,t and about ten feet below the surface the palmata or handshaped coral. In the shallow mud between the reefs and the continent, there are multitudes of branching corals of the most beautiful forms, colors, and delicacy of structure. The production of coral rock is explained partly by the mechanical action of the waves, and partly by the destruction of the coral insect by the sea urchin and other animals that feed on it. The waves disintegrate the structure formed by the animal, and then roll back the coral sand, thus produced upon it, where it undergoes a process of induration in the course of time.

"It is an interesting question how the structure ever rises above the water level, seeing that the animal which makes it cannot live out of the water. The little architects retain enough sea water to last them over until the next tide, and are so enabled to work up to the highest watermark. Actinia have been observed all closed up on the rock at low water, and then suddenly opened like magnificent flowers, five and six inches in diameter, when the tide rose."

So far, what Mr. Agassiz says of them; now let us try and look at them ourselves. In the hot, summer months, when the waters are bringing forth the moving creature that has life, millions of diminutive, jelly-like spawn are thrown out by the parent animal. For a while, they enjoy their freedom, and seem to luxuriate in the exercise of their powers of locomotion, which they are never hereafter to recover; but soon they become weary, and settle down upon some firm, stationary body. At once they begin to change their form; they become star-like, the mouth being surrounded by tentacles, very much as the center of a flower is surrounded by its leaves. After some time, each one of these ray-like parts pushes out extensions, which in their turn assume the shape of tiny stars, and establish their own existence by means of an independent mouth. In the meanwhile, lime has been deposited at the

Astræa, a coral in the shape of a star.

† Meandrina, a genus of corals wich meandering cells, as the brain-stone coral.

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base of the little animal, by its own unceasing activity, and forms a close-fitting foot, which adheres firmly to the rock. Upon this slender foundation arises another layer, and thus by incessant labor, story upon story, until at last a tree has grown up with branches spreading in all directions. But where the plants of the upper world bear leaves and flowers, there buds forth here, from the hard stone, a living, sensitive animal, moving at will, and clad in the gay form and bright colors of a flower.

This flower is the animal itself, seen only in its native element, and unfit for air and light. What we call coral is its house, outside of which it prefers to live, rather than within.

How they build their dwelling, human eye has never seen. We only know that the tiny animals, by some mysterious power, absorb without ceasing the almost imperceptible particles of lime which are contained in all salt-water, and deposit them, one by one, in the interior. This is done, now more, now less actively; and the denser the deposit is, the more valuable the coral. Gradually this substance hardens and thickens, until, in the precious coral, the Isis Nobiles of science, a large tree is formed, which often reaches the size of a man's waist. It is perfectly solid and compact, and adorned on the surface with delicate parallel lines. Thus, on the tree-shaped limestone, grows the life-endowed body of the polypus; it moves, it feeds, it produces others, and then is turned again into stone, burying itself in its own rocky house, whilst on its grave new generations build unceasingly new abodes.

This is the so-called blood-coral, the favorite of antiquity, and the fashion of our day-next to the pearl, the most precious jewel of the deep.

It is not easy to obtain a piece of living coral, for the purpose of studying its wondrous structure, and admiring its exceeding beauty. The great depth at which the mysterious little animals dwell in the ocean, secures them against the mere amateur fisherman; and the professional coral-fisher in the Mediterranean, the son of superstitious races of Southern