. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 54 THREE CRUISES OF THE " BLAKE. nessee Reef. At other points it forms extensive shoals, which are covered with a few feet of water. In other localities again, the pounding of the breakers on the edges of the reefs has ac- cumulated dead corals which form small keys along the line of the main reef, as at Sand Key, Sombrero, and the Samboes. There are passages of greater or less depth across several parts of the reef, giving access from the Gulf Stream to the interior ship channel. The main entrances to K
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 54 THREE CRUISES OF THE " BLAKE. nessee Reef. At other points it forms extensive shoals, which are covered with a few feet of water. In other localities again, the pounding of the breakers on the edges of the reefs has ac- cumulated dead corals which form small keys along the line of the main reef, as at Sand Key, Sombrero, and the Samboes. There are passages of greater or less depth across several parts of the reef, giving access from the Gulf Stream to the interior ship channel. The main entrances to Key West Harbor are formed by such channels. The depth of water on the reef, like that of the mud flats, increases as one passes from Cape Florida towards Sand Key and the Marquesas. The small keys of the reef proper are built of accumulations of larger coral boulders forming the foundation pieces of corals, and fragments of shell and coral sand arranged according to their size in the interstices, and heaped up by the action of the waves, the tides, and the winds. Similar agencies must have formed the keys proper, for they consist of the same coral rock and sand, acted upon for a much greater length of time by the storms. A walk along the sea-face of any one of the keys will show its coast line to be in incessant movement. In exposed places. Fig. 36. — Coral Breccia. Fig. 37. — Coral the larger fragments broken off by the breakers from the coral rock of the shores are split into smaller fragments, which in their turn are changed to pebbles, and then finally become cemented into coarser or finer sand or impalpable powder. The cementation of these fragments at different stages gives us the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge,
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