On coral reefs and islands . i Lebu and Vanua Lebu,within the inner reefs, a distance exceeding two hundred island of Tahiti on its northern side presents us with a goodillustration of a narrow channel, and at the same time exhib-its the usual broken or interrupted character of reefs. This isseen in the following cut in which the reefs, both fringing andbarrier, are the parts enclosed by dotted lines. The outer reef 14 ON CORAL REEFS AND ISLANDS. extends half to two-thirds of a mile from the shore. Withinit, between Papieti and Matavai, there is an irregular ship chan-nel, varying fr
On coral reefs and islands . i Lebu and Vanua Lebu,within the inner reefs, a distance exceeding two hundred island of Tahiti on its northern side presents us with a goodillustration of a narrow channel, and at the same time exhib-its the usual broken or interrupted character of reefs. This isseen in the following cut in which the reefs, both fringing andbarrier, are the parts enclosed by dotted lines. The outer reef 14 ON CORAL REEFS AND ISLANDS. extends half to two-thirds of a mile from the shore. Withinit, between Papieti and Matavai, there is an irregular ship chan-nel, varying from three to twenty fathoms in depth. Occasionallyit enlarges into harbors; and in other parts it is very intricate,though throughout navigable by large vessels. The island ofUpolu, of the Samoati Group, is bordered by a reef nearly a milewide on part of its northern shore; but the waters within are tooshallow for a canoe at low tide: and therefore, notwithstandingits extent, the reef is rather a fringing than a barrier l mile. 3QgCjtS& PART OK THE NORTH SHORE OF TAHITI. The bottom of the channels or lagoons takes its charac-ter, as regards the material constituting it, either from the reefs, asource of calcareous sand and fragments, or from the earthy detri-tus of the island streams. At Upolu, the white coral sand of thereefs, (or in more general terms the reef debris,) forms the bottom ;in some places it had the consistence of mud, and it was seldomobserved to be covered with coarse material. There were somesmall patches of coral over it, and here and there a growing massof Porites. The fresh waters of the shores do not flow over thesewide reefs as there is no proper inner channel, and there is conse-quently no shore detritus mingled with the reef debris. At Ta-hiti, the sounding lead usually brought up sand, shells, and frag-ments of coral. At Tongatabu, the bottom, where the Peacockanchored, was a grayish blue mud, appearing as plastic as com-mon clay; it consisted so
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Keywords: ., bookcentury1800, bookdecade1850, bookidoncoralreefs, bookyear1853
