The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1902-06-22
HOW CORAL A K ISLANDS.
Result of Investigations by DR.. Agas-
sfz in the M~aIdives.
Brooklyn Eagle.

Brooklyn Eagle.
DR.. Alexander Agassiz, of Harvard, for
many years director of the Museum of Com
parative Zoology-better known, perhaps,
as the Agassiz Museum, from its founder,
DIR. Agassiz's father, Louis Agassiz, the
great Swiss-American naturalist-has re-
turned TO this country from an extensive
examination of the coral formations In
and around the Maldive islands, in the In
dian ocean, off the southern coast of Ceylon.
DR.. Agassiz said that he had learned more
about corals in this single expedition than
liz fifteen years of previous study else
where, and he brings back with him to add
to the remarkable coral collections already
gathered in the Museum of Comparative
Zoology many specimens of the greatest
rarity, some of which are altogether new TO
science. DR.. Agassiz's assistants in this ex-
petition were his son. Macmillan Agassiz,
DR.. w. Mem. Woodwork and II. B. Bige-
low. Beside the corals themselves. a large
number of photographs were secured, to-
gether with an chronological collection of
great interest, the larger part of which was
obtained through the friendliness of the
Sultan of the Maldives, to whom DR..
Agassiz carried letters from the royal Gov
ernor of Ceylon.
The general formation of coral islands, or
atolls, is familiar from the descriptions
which the school Biographies give. Most of
them have, in a general way, the shape of
an extended crescent-so extended as nearly
to make a ring inclosing a body of water
which Is called the lagoon. Frequently the
ring is broken on one side, giving free pass
age to the sea, but in the course of time
1t tends to become completely closed. The
winds and the tides deposit sand upon the
top of the coral formation, and vegetation
even trees of good size-gradually takes
root. Some Of the atolls are composite
atolls within atolls, as it were-the outer
ring being generally detached reefs which
stand about the main structure in a roughly
outlined circle.
Professor Agassiz says that the lagoons
of the Maldives were richer in their con-
tributlonS to the study of coral than any
others he ever visited. The expedition
started from this country last October, and
covered some 1,6O miles after it reached
the Maldives. The steamer Amra was char
tered from the British India Steam Naviga-
ton Company and equipped with a sound
ING machine built specially for the pur-
poses of deep sea investigation, a second
sounding machine for more moderate
depths of water in The lagOons within the
coral reefs, and with a steam winch and
drum for sea-towing and dredging. Inter
esting information regarding the topog-
raphy of the bottom of the ocean in the
vicinity of the Maldive atOlls was obtained
from the sOundings made possible by this
apparatus-the general conclusion being
that the atolls rose from a broad level
plateau which forms the bed of the sea in
this locality. The greatest depths of the
lagoons of the composite coral atolls were
found to be much more than forty fathoms.
In some places the variations of the floor
of the ocean were very abrupt. the depth
of the water above them changing from
eight to over twenty fathoms in short dis
tances. But in the center of the channel
between two of the islands 769 fathoms of
water was found, and in a wide channel
elsewhere the sounding reached 1892 faith
oms-the latter depth representing, appa-
rently, the normal depth of the plateau.
The smaller atOlls vary in size, DR..
AgassiX found, from a couple of hundred
feet in diameter to seven miles in length.
Numerous nascent atolls were observed.
many of which exist as flats, bars or mere
rings which do not rise more than five or
six fathoms from the top of the plateau,
others coming within from three to seven
fathoms of the surface of the sea, others
again which form rings or bars just awash
or with a foot or two of sea over the rim.
and, finally. some rings that are partially
awash, but with little sandbanks projecting
a few inches above the surface. The shape
of these islands is not necessarily circular:
it varies greatly and is indirectly affected
by the topography of the sea bottom. Some
are elliptical, crescent or p~ear-shaped, while
in others the lagoons have been formed by
the growthS of coral patches-rising at a
short distance parallel with the outer reef
which have become Joined.
The strength of the winds that prevail
among the Maldives has much to do, DR..
AgassiZ SAYS, with the shape that the
islands assume. There are none of the
great breakers which pound upon the reefs
OF the CentIdl anu western racine TO IdSn-
ion the Maldives. The beaches are un-
usually steep and are rarely more than five
or six feet high, and the reef rocks are Of
the most modern character and are so worn
as to indicate that they once rose three or
four feet higher than at present. The
growth Of cOrals in the lagoons of the Nal
dives is very fne-in marked contrast with
the scanty growth i'm the Pacinc groups,
where DIR. AgassiZs previous expeditions
have for the most part taken him. They
are found in great quantities on the outer
| slopes of the ring-like bits of land-either
thrust out from the edge or even far up on
the little sharp beaches. and down as far
as a depth OF from eight TO twelve fathoms.
| Altogether the report of DR.. Agassiz's re-
! searches which he has in preparation for
the Harvard Museum of Comparative FOOL
ogy promises to be an unusually interesting
and valuable contribution 10 the literature
OF this special branch Of natural history.