New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1851-05-15
EVENING SESSION.


oftbe Mechanics Institute was filed at an early
bopr and the appearance OF the Professor was
erected with hearty applause. His remarks oc
cuoied about an hour and q hall, and were heard
throughout with marked attention.
On occount Of the important nature OF these
statements of Prof Agassiz, beside being the nrss
occasion on which they have been given to the
public, l send you q full abstract OF bis remarks
REsrr4Ts or AN EXPLORATION OF The CORAL
REEFS or FLORIDA
IN CONNECTION WITH The COAST SURVEY
It has recently been my good fortune, said Prot'
Aeassiz. 10 have an opportunity Of exploring the
Reefs Of Florida under the ausp ces OF the United
States Coast Survey, with a view OF Investigating
the character Of the coast and the structure OF its
extensive range Of COrals.
The Superintendent OF the Coast Survey Prof.
Bacbe. had afforded him every facility for prose-
cotipg his Investigations, and had desired him TO
reuert the results obtained, with vie OF being
usefol 10 the Typographical inyestig cations going
/ IN under Prof direction. Prof Agasslz ex-
plessed his great obligation to the S1perlntend'
eur and the Intelligent officers OF the Survey, Tor
assistance and information which had enabled
him TO obtain results that might otherwise have
REQUIRED months and perhaps years, oil careful
| observation. He hoped these results would prove
n, useful as they had been instructive 20 himself.
At the outset, he would say that the Coral
Reefs Of Florida differ entirely from the Coral
reefs of other seas, which have been 90 ably
described by Nessrs. Dana aud Darwin BY Mr..
| Darwin in the British Exploration under Capt
| Fitzroy, and by MIR Dana 10 the United States
! Exploring Expedition under command Of Capt.
/ Wilkes
In order 10 point out the peculiar characteristics
! of the Reef OF Florida, it would be necessary 10
speak Of the reefs OF other regions, and parslco ar
/ " those of the Pacific. These ore divided lnIo
! three clssses viz the Frnging Rect, the Bar
/ rer Reef and Atolls or Lagoons- isands. The
characters Of each of these divisions fully justify
/ such classification. But in the case OF the
! Florida Reef the Coral formations extend in sew
eral parallel ridges between the main land OF
! Florida and the Gulfsresm, in a westerly
| course diverging more and more from the main
| land. until, near Cape Sable they are forty miles
distant; stretching like broad arm into the Gull
| Of Mexico and extending in southerly dlrec'
| ton into the rapid current OF the GGfSTeRm
| The Pacific Ocean reefs on the contrary, grow IN
the open sea, and differ essentially in character
! from those OF Florida.
The principal reef Of diving corsls in Florida
occurs between the main Keys and the rapid sea
! current " hch runs between CUBA and the Islands
epcirolipg the main land OF Florida, but other
coral deposits of a peculiar nature are found 20
exist around, upon and between the Keys and the
| main land. The combined action Of the tides aud
! currents produces eddies IN which fine sand and
/ even mud is Deposited around the reefs. These
I
/ fragments. or impalp able powder. held in
/ pension by the water, which is rendered milky
white by their presence. At short distance DC
| youd, the water becomes clear.
The three classes Of Coral Reefs distinguish
able elIe here, were explained by Prof with
| the aid Of blackboard diagrams. First the
ringing reefs > secondly, the barrier reefs"
which form rising walls at some distance tom the.
main land, between which and the land a broad
and snie channel frequently exists; and thirdly,
a ~ & QF isl "a
walls, sometimes continuous, and sometl nes
broken up The lagOOns often constitute Rccessi-
bic and safe bsrbors. These encrchDg reefs are
formed ia a similar manner to the barrier reefs,
by the growth of Coral from an unknown depth
10 The surface. The formation of the two latter
classes Of reefS has been sscribed 20 the sQbsi-
dence of the bottom, combined with the upward
growth of the cOras.
The range of living, reef building Corsls has
been ascertGined TO be limited between depth
Of sixteen to twenty fathomS, and few inches
below low water mArk-for unless constantly
submerged, they die; but they are frequently
found dead at enormous depths forming walls OF
coral rocks very preclpitous
In Florida we have DO barren reef, but 4 series
Of conceptrc reef, enclosing parallel channels
formed without the slightest Indication Of sab
mergence or upheaval. There are the Outer
Reef the Florida Keys and the Shore Bluffs, with
the main channel south OF the Keys the mad
fats between the Keys and the main land, with
a slight depth Of water, often lot more than two
feet; and fiat, low islands, on which there is al
extensive growth Of mangroves The Keys rise
from ten to twelve, seldom thirteen feet above
the level OF the Ocean. Near the Shore there
are mud and coral sand accumulatons which are
evidently the results Of the decomposition Of the
solid parts Of the corsls themselves.
Beyond the Keys, the channel is from dve 10
six and seldom more fatboms deep. It's boun-
dAries are frequently indicated by small Isl
ands or shoals, some Of which form very dan.
gerous reefs, such as Carisford reef IL 10
within this channel that She wreckers take up
their abode, being safely sheltered from the strong
gales which blow frequently outside, behind the
v ais of the Outer Reef sndth bar islands rising
for 4 few feet above the level Of the ocean No
coast said Prot A il more secure and safe navi-
cation than this, If il be properly understood
every twenty miles there is the broadcast and |
safest harbor to run into But at present, it 10 |
perhaps more dangerous 10 know of these harbors |
than 10 be ignorant Of their existence for the /
lights and signals along the shore are located |
without reference 70 using these places Of refuge
AdvertiDg TO The geological and geological char. |
Acter Of the general reef the Professor remarked
that Il was important 10 ascertain whether az re.
ported by some, the reef consisted Of dead coras
only or, as others maintained was composed of
living corRs still growing and extending; or
whether, as it bad been asserted by others il con.
sIted only ofooitic rocks containing no indications
Of coTAls whatever.
M tHeso 3io icNEo " % CoHAASent,
with the qualification that toe three classes occ0.
py different localities On'the Outer Reef from
Cape Florida to Key West, IN from ten 70 twelve
faEh0mS up 10 the surface Of the water living cor
as are found greatly differing, however, in con.
stIution-ihe AadTepores tNadrePoya Dalmata,l |
especially, rising 10 the very surface, while the
commonly 90 called Brain Cora l3foaHdrtna) oc.
ours In the lower, and the Astrea stilI lower |
levels Specimens OF the different species were |
exhibited. The Madrep0Ta p1lEsata form extern
sive fields Of powerful stems, branching and ex.
banding resr the surface into large hats, resting
upon strong baseI, and presenting the appearance |
Of leaves spread out The Professor character.
lied these helcs AZ wonderful spectacle. This
extensive growth does not occur, however. further