Coral Reefs; Volcanic Islands; South American Geology — CompleteDarwin, Charles
Science
Coral Reefs; Volcanic Islands; South American Geology — Complete
Darwin, Charles
Beagle Expedition (1831-1836); Coral reefs and islands; Geology -- South America; Islands; Volcanoes
SANDWICH ARCHIPELAGO.—_Hawaii_; in the chart in Freycinet’s “Atlas,”
small portions of the coast are fringed by reefs; and in the
accompanying “Hydrog. Memoir,” reefs are mentioned in several places,
and the coral is said to injure the cables. On one side of the islet of
Kohaihai there is a bank of sand and coral with five feet water on it,
running parallel to the shore, and leaving a channel of about fifteen
feet deep within. I have coloured this island red, but it is very much
less perfectly fringed than others of the group.—_Maui_; in Freycinet’s
chart of the anchorage of Raheina, two or three miles of coast are seen
to be fringed; and in the “Hydrog. Memoir,” “banks of coral along
shore” are spoken of. Mr. F. D. Bennett informs me that the reefs, on
an average, extend about a quarter of a mile from the beach; the land
is not very steep, and outside the reefs the sea does not become deep
very suddenly; coloured red.—_Morotoi_, I presume, is fringed:
Freycinet speaks of the breakers extending along the shore at a little
distance from it. From the chart, I believe it is fringed; coloured
red.—_Oahu_; Freycinet, in his “Hydrog. Memoir,” mentions some of the
reefs. Mr. F. D. Bennett informs me that the shore is skirted for forty
or fifty miles in length. There is even a harbour for ships formed by
the reefs, but it is at the mouth of a valley; red.—_Atooi_, in La
Peyrouse’s charts, is represented as fringed by a reef, in the same
manner as Oahu and Morotoi; and this, as I have been informed by Mr.
Ellis, on part at least of the shore, is of coral-formation: the reef
does not leave a deep channel within; red.—_Oneehow_; Mr. Ellis
believes that this island is also fringed by a coral-reef: considering
its close proximity to the other islands, I have ventured to colour it
red. I have in vain consulted the works of Cook, Vancouver, La
Peyrouse, and Lisiansky, for any satisfactory account of the small
islands and reefs, which lie scattered in a N.W. line prolonged from
the Sandwich group, and hence have left them uncoloured, with one
exception; for I am indebted to Mr. F. D. Bennett for informing me of
an atoll-formed reef, in latitude 28° 22′, longitude 178° 30′ W., on
which the _ Gledstanes_ was wrecked in 1837. It is apparently of large
size, and extends in a N.W. and S.E. line: very few islets have been
formed on it. The lagoon seems to be shallow; at least, the deepest
part which was surveyed was only three fathoms. Mr. Couthouy
(“Remarks,” p. 38) describes this island under the name of _ Ocean_
island. Considerable doubts should be entertained regarding the nature
of a reef of this kind, with a very shallow lagoon, and standing far
from any other atoll, on account of the possibility of a crater or flat
bank of rock lying at the proper depth beneath the surface of the
water, thus affording a foundation for a ring-formed coral-reef. I
have, however, thought myself compelled, from its large size and
symmetrical outline, to colour it blue.
Public-domain text, read in full here on John Shaqi.
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