io8 



THE MUSEUM. 



so called from a fanciful resemblance 

 to the human brain. Third, by bud- 

 ding. Small bud-like excresences, 

 branch out from the outer sac. near 

 the point of union with the calcareous 

 matter which it has deposited, and to 

 which they attach themselves, and 

 thus form independent polyps. Be- 

 sides, if any portion of the living polyp 

 be broken from the parent stock, it 

 may take root and grow, and from a 

 nucleus for a new colony. 



The coral polyp cannot live at the 

 surface, nor at a depth of more than 

 one hundred feet, nor in water the 

 temperature of which is less than sixty- 

 eight degrees above zera. Specimens 

 of coral, however, are found in all 

 parts of the world and at various eleva- 

 tions, both above and below the sea 

 level, thus showing that neither the 

 temperature, nor elevation is the same 

 now that it has been at various periods 

 of the world's history. It is even 

 claimed by some, (and the advocates of 

 this theory number some of the most 

 eminent geologists,) that the limestone 

 rocks of the St. Lawrence valley, and 

 of the upper part of the Missouri river, 

 and in New Jersey, and a few other 

 places are but coral formations which 

 have been metamorphosed by the ac- 

 tion of heat. The hypothesis is rather 

 bold, but not at all improbable. In 

 the South Pacific Ocean, coral has 

 been taken from the rocks at a depth 

 of more than twelve hundred feet; it is, 

 however, never found, in this region, 

 at a greater elevation than it could 

 have been thrown by the waves. This 

 demonstrates that the islands in that 

 locality have slowly settled, and adds 

 another link to the chain of evidence 

 which connects the Pacific Archipelago 

 with an extensive continent which 



formerly occupied that portion of the- 

 globe. 



In general appearance coral' islands 

 much resemble one another. They 

 are all level, and raised but a few feet 

 above the surface of the ocean. They 

 invariably rest upon the top of a sub- 

 merged mountain, which they generalh- 

 encircle; and they reproduce to a cer- 

 tain extent the contour of their base. 

 Generally they are in the shape of a 

 circle, more or less elongated, and in- 

 close, within the ring, a shallow body 

 of water which is termed a lagoon. 

 Sometimes, however, the lagoon be- 

 comes filled and the whole constitutes 

 a single, circular island. Then, too, 

 the surrounding circle is often broken, 

 sometimes into numerous pieces, so 

 that, instead oi a ring surrounding a 

 lagoon, there may be hundreds of little 

 islands. This is especially noriceable 

 in the Maldine Archipelago, whose 

 chief styles himself, "Sultan of Twelve 

 Thousand Islands. " The flora of a 

 coral island numbers but a very few 

 species, and its fauna, still fewer. Its 

 soil is composed almost wholly of 

 carbonate of lime, sometimes covered 

 with a deposit of decayed vegetable 

 matter. 



The tendency of the polyp is to grow 

 upward, but, when it reaches the sur- 

 face it is obliged to turn, and, growing 

 • laterally, it forms huge, overhanging 

 masses, which arc broken off by the 

 waves, and thrown upon the top (^f the 

 formation. This is repeated, again 

 and again, until an island, ten or 

 twelve feet above the surface of the 

 ocean, has been formed, (iradually 

 sea-weed, and other organic substan- 

 ces, are thrown upon the island by the 

 action of the waves, and these, decay- 

 ing, become; mixed with the calcareous. 



