3 
terior cavity, which thus becomes more or less 
filled up, and a low island is formed to which 
floating " seeds are carried, that take root and 
flourish. A barrier reef only differs from an 
atoll in that it runs parallel with some large 
island or continent, from which it is separated 
by a broad, deep channel j the outer side sinks 
at a sharp angle into deep ocean. The fringing 
reefs have only a narrow and shallow channel, 
between them and the land where the water 
on their outer side has small depth. Wow it 
appears that the coral animals cannot live at a 
greater depth than -thirty fathoms, and if ex- 
posed to the direct rays of the sun, uncovered 
by water, it will perish. A consideration of 
these facts has led a learned naturalist to form 
a theory, which has generally been accepted 
by scientific men. He believes that the 
phenomena in question are connected 
with movements which simultaneously 
affect large portions of the earth’s crust, such 
as that by which the coast of Sweden, to the 
extent of some hundreds of miles, is now being 
elevated. He thinks that atolls have then- 
foundation on land, which has subsided and 
part of which was onceabove thelevel of the sea ; 
that barrier reefs show that the laud near 
which they are situated is likewise sinking, and 
that fringing reefs on the other hand, denote 
that the land is either rising, as in the majority 
of the Sandwich Islands, where old reefs have 
been elevated to a considerable distance above 
the sea, or that the land is stationary. An ex- 
amination of the chalk and limestone beds of 
the earth’s crust, shows that they are in great 
part composed of corals, all the species of 
which are extinct. Hence it may be con- 
jectured, that the labours of existing zoophytes 
will remain to after ages in the shape of cal- 
careous beds when the species themselves will 
have disappeared. The foregoing remarks have 
principally been gleaned from the best authorities 
available here. There is one portion of 
what I have just quoted, which is of 
great importance to U3 generally, and 
which demands the particular attention of 
this society. I allude to the theory that the 
[ existence of barrier reefs shows that land near 
which it is situated is sinking. If this 
hypothesis is correct, and as we are 
exactly in this position, so far as 1000 
miles of our N.E. seaboard is concerned, 
it would be highly interesting to test it by actual 
observations, which might easily be made by 
residents at our Northern Ports, and although 
the process of subsidence may be very slow, 
still the coast-line would always show sufficient 
indications to confirm or confute such a theory 
a s applicable to our own particular case. 
Having, as I consider, stated all that is neces- 
sary for the introduction of my subject, so far 
at least as regards its scientific bearings, I will 
now proceed to state my own impressions and 
experiences during nearly three years, a greater 
portion of which was spent amongst the Mai* 
dive Islands and Chagos Archipelago. My 
object is not to enter into a description of these 
islands, so much as to endeavour, to convey my 
own general impressions regarding them as 
merely coral formations. On approaching these 
islands a slight indistinct fringe is observed on 
the horizon, which, as the vessel gradually 
draws nearer, assumes a denser appearance, 
and soon the tall graceful cocoanut palms, the 
gigantic banyan (ficus indicus), the bread fruit 
tree, the banana, and a variety of other trees, 
plants, and bushes are developed, and a wreath 
of white foam is seen as the breakers of the 
ocean dash heavily against the barrier reef, and 
apparently threatening, in their fury, to wash 
away the fairy islands which seem to have 
suddenly risen out of the sea. As the 
ship draws near, the reef seems to be 
one unbroken line of breakers, and to one who 
for the first time approaches such a scene, it 
causes rather a nervous sensation, and the 
danger of being dashed to pieces seems immi- 
nent. Presently an interruption is observed in 
the line of breakers, and a channel is seen 
through a chasm of the reef, through which 
the ship glides into a beautiful smooth lagoon. 
The sudden transition from the rough chopping 
sea outside to the quiet lake-like water within the 
lagoon, is something delightful. It is true that 
the heavy dull sound of the sea, as it breaks on 
the barrier reef, is still heard, but it only tends 
to realise the security which one feels in being 
snug at anchor in smooth water. The water 
within the lagoon is of an emerald green color, 
whilst that which has been left outside is of the 
deepest blue. Let us fancy the ship securely 
anchored in the centre of an atoll of about seven 
miles in diameter; the barrier reef we will 
suppose to be about a quarter of a mile broad 
from its outer to its iuner circle. Let us 
imagine it to be low water, and the whole reef 
exposed to view. On a portion of the inner 
circle of reef is a low sandy beach, above which 
a bank, seldom more than six feet higher than 
high water mark, the rise and fall of the tide 
being, say, four feet, is covered with an under- 
growth of low shrubs, above which the cocoa- 
nut palms and other trees rise. This bank 
may extend outwards to one-fourth or more of 
the barrier reef, and forms a habitable island, 
upon which the natives build their habitations. 
At high water the barrier reef is covered, but 
not to any depth, by the sea, the fury of which 
is overcome upon the outer barrier, otherwise 
the low island just described would soon he 
washed away. We have already imagined that 
it is low water. Let us further accede that the 
weather is calm, and the sea outside perfectly 
smooth. We take advantage of these favourable 
circumstances to take a stroll to examine the 
barrier reef, which is composed of various de- 
scriptions of corals and dead shells. Our pro- 
gress is slow, owing to the unevenness of the 
ground, and the necessity for avoiding deep 
fissures and channels which have not yet been 
