File:Corals and coral islands (1874) (18109834905).jpg

Title: Corals and coral islands
Identifier: alr2577.0001.001.umich.edu
Year: 1874 (1870s)
Authors: Dana, James Dwight, 1813-1895
Subjects: Coral reefs and islands; Corals
Publisher: New York, Dodd & Mead
Contributing Library: University of Michigan
Digitizing Sponsor: University of Michigan

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Text Appearing Before Image:
176 CORALS AND CORAL ISLANDS, breakers. In these shallow waters are the growing corals; yet, as before stated, a large part is often barren sand or coral rock, especially where the depth is over fifty feet.
Text Appearing After Image:
SECTION OF THE KIM OF AN ATOLL. From atohi^ the shore platform or reef-rock, nearly at low-tide level, with the margin (a) slightly elevated, and usually mucih incrusted at top with Nullipores. From the platform there is a rise, by a steep beach (b c), of six or eight feet, to the wooded part of the coral belt represented between c and d. From d to e there is a gently sloping beach bordering the lagoon. Beyond 6, the waters of the lagoon at first deepen gradually, and then fall off^ more or less abruptly. In the Paumotus, the shore platform, the steep beach, and the more gently sloping shore of the lagoon are almost con- stant characteristics. The width of the whole rim of land, when the island gives no evidence of late elevation, varies from three hundred yards to one-third of a mile, excepting certain prominent points, more exposed to the united action of winds and waves and often from opposite directions, which occasionally exceed half a mile. The shore platform is from one to three hundred feet in width, and has the general features of a half-submerged outer reef. Its peculiarities arise solely from the accumulations which have changed the reef into an island. Much of it is commonly bare at low tide, although there are places where it is always covered with a few inches or a foot of water; and the elevated edge, the only part exposed, often seems like an embankment preventing the water from running off. The

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