Beagle Expedition (1831-1836); Coral reefs and islands; Geology -- South America; Islands; Volcanoes
much less extensive than round the other islands in the group.
MADAGASCAR.—My information is chiefly derived from the published charts
by Captain Owen, and the accounts given by him and by Lieutenant
Boteler. Commencing at the S.W. extremity of the island; towards the
northern part of the _Star Bank_ (in latitude 25° S.) the coast for ten
miles is fringed by a reef; coloured red. The shore immediately S. of
_St. Augustine’s Bay_ appears fringed; but _Tullear_ Harbour, directly
N. of it, is formed by a narrow reef ten miles long, extending parallel
to the shore, with from four to ten fathoms within it. If this reef had
been more extensive, it must have been classed as a barrier-reef; but
as the line of coast falls inwards here, a submarine bank perhaps
extends parallel to the shore, which has offered a foundation for the
growth of the coral; I have left this part uncoloured. From _lat_. 22°
16′ _to_ 21° 37′, the shore is fringed by coral-reefs (see Lieutenant
Boteler’s “Narrative,” volume ii., page 106), less than a mile in
width, and with shallow water within. There are outlying coral-shoals
in several parts of the offing, with about ten fathoms between them and
the shore, and the depth of the sea one mile and a half seaward, is
about thirty fathoms. The part above specified is engraved on a large
scale; and as in the charts on rather a smaller scale the same fringe
of reef extends as far as latitude 33° 15′; I have coloured the whole
of this part of the coast red. The islands of _Juan de Nova_ (in
latitude 17° S.) appear in the charts on a large scale to be fringed,
but I have not been able to ascertain whether the reefs are of coral;
uncoloured. The main part of the west coast appears to be low, with
outlying sandbanks, which, Lieutenant Boteler (volume ii., page 106)
says, “are faced on the edge of deep water by a line of sharp-pointed
coral-rocks.” Nevertheless I have not coloured this part, as I cannot
make out by the charts that the coast itself is fringed. The headlands
of _Narrenda_ and _Passandava Bays_ (14° 40′) and the islands in front
of _Radama harbour_ are represented in the plans as regularly fringed,
and have accordingly been coloured red. With respect to the _East coast
of Madagascar_, Dr. Allan informs me in a letter, that the whole line
of coast, from _Tamatave_, in 18° 12′, to _C. Amber_, at the extreme
northern point of the island, is bordered by coral-reefs. The land is
low, uneven, and gradually rising from the coast. From Captain Owen’s
charts, also, the existence of these reefs, which evidently belong to
the fringing class, on some parts, namely N. of _British Sound_, and
near _Ngoncy_, of the above line of coast might have been inferred.
Lieutenant Boteler (volume i., page 155) speaks of “the reef
surrounding the island of _St. Mary’s_ at a small distance from the
shore.” In a previous chapter I have described, from the information of
Dr. Allan, the manner in which the reefs extend in N.E. lines from the
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account