Page:Popular Science Monthly Volume 76.djvu/401

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EARLY seventy miles west of Key West, out in the Gulf of Mexico and in the most isolated situation occupied by any islands off our coast, lie the seven small keys of the Tortugas. Between them and the Cuban coast flows the great current of the Gulf Stream, and to the eastward of them lie forty miles of open water beyond which are their nearest neighbors, the Marquesas Keys of Florida. The Tortugas are the most westerly and southerly and the newest geologically of all those coral and limestone islets which are strung chain-like one after another in a long graceful sweeping curve from Cape Florida southward and always westward to end in the Tortugas.

The Tortugas Keys are low, being only as high as the winds and waves can toss the shifting sea-sands which compose them, for they consist entirely of wave-broken fragments of shells with here and there the stony skeleton of a seaweed, echinoderm or dead coral. Every particle composing them was once part of a living creature in the ocean which surrounds them, and thus the islands are but the dead remains of living things that were. A stunted twisted growth of bay cedars and cactus clings to their sandy soil and defies the salt spray which in time of storm drives completely over the islands. Almost every plant surviving upon the Tortugas is tough-leaved and juicy inwardly, or it sends roots far down through the sand to the salt water, for the rain serves but poorly to moisten the loose sandy soil through which it filters rapidly. The Tortugas Keys constitute the rim of an irregular atoll enclosing a lagoon with many a coral patch rising ominously out of deep blue water to within a few feet of the surface. In the old days tradition says that its harbor was the retreat of many a pirate safely anchored in the midst of the maze of its coral reefs.

Yet the islands, although remote, are not desolate to the naturalist, for all around them lies the deep blue of the tropical ocean, its ripples flashing merrily in the brilliant sun, and looking downward through the crystal depths one floats above the richest coral reefs of the Florida region. No butterflies of an East Indian jungle outrival the brilliant fish which glide languidly in and out among the purple sea-fans bending majestically to the surging sea. Hundreds of creatures find their homes among the caverns of the coral reef, or under the great carpets of rich yellow and olive sea-anemones which overgrow the naked rock