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Page:Popular Science Monthly Volume 32.djvu/331

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distance by their slight differences in contour. The position of our key, which we had left behind, was shown by the top of its tall cocoanut palms long after the island itself had dipped below the water. Taking a northwest course up the channel, Abaco is seen as a low barrier on our left, while at a greater distance it looks like an undulating green ribbon between the sky and sea. We pass numerous small keys

PSM V32 D331 Green turtle key bearing 3 miles northeast.jpg
Fig. 2.—Green Turtle Key, bearing three miles Northeast. (From a sketch made from the deck of a schooner.)

and rocks on the right, between which long white lines of breakers may be seen, marking the outer reef. We are frequently near enough to the "mainland" to see its dense forests of pine, its palms fringing the shore, the narrow beaches of white coral-sand, with here and there a thatched hut fronting a pineapple field, which may be distinguished by the small clearings in the woods.

The keys present the greatest variety in size and form, from a bare rock no larger than a buoy to islands five or six miles long. The latter are very narrow, and are usually covered with a thick growth of shrubs and small trees which, excepting a few palms, rarely exceed fifteen or twenty feet in height. The islands are scattered along closely together, or occasionally separated by wide channels. The soil has to be very thin indeed, which can not support a variety of shrubs, which seem to grow out of the very rocks and to live upon the air. Some of the smaller keys are mantled with vines and climbing plants, such as smilax, convolvuli, and rock samphire, with here and there some low shrubbery at the water's edge.

The coral-rock which forms the basis of the islands crops out at many points, and is always exposed around the shores where these are not covered by a sand-beach. Freshly-broken surfaces have a light-cream color, but weather to a uniform grayish tint. This limestone is so soft that it can be readily sawn or chopped with an axe. Consequently, the waves denude it rapidly, forming the white coral-sand, which is distributed as a fine deposit over the sea-bottom and as stretches of smooth beach. The shores overarch where they are at all precipitous, roofing a wide cavern below, in which the ceaseless roar of the waves may be heard at a long distance. Where a single rock