CORAL ISLANDS. Ig! 
struck with the appearance of certain islands, which presented a con- 
formation altogether singular. In 1601, Pyrard de Laval, speaking 
of the Malouine (now the Falkland) Islands, said :—‘‘They are 
divided into thirteen provinces, named azod/ons, which is so far a natural 
division in that place, that each atollon is separated from the other, and 
contains a great number of smaller islands. It is a marvel to see 
each of these atollons surrounded on all sides bya great bank of stone— 
walls such as no human hands could build on the space of earth 
allotted to them. These atollons are almost round, or rather oval, being 
each about thirty leagues in circumference, some a little less, others 
a little more, and all ranging from north to south, without any one 
touching the other. There is between them sea channels, one broad, 
the other narrow. Being in the middle of an atollon, you see all around 
you this great stone bank, which surrounds and protects the island 
from the waves; but it is a formidable attempt, even for the boldest, 
to approach the bank and watch the waves as they roll in and break 
with fury upon the shore.” 
Since the publication of Laval’s description, many circular isles, or 
groups of islands, analogous to these atollons, since called azol/s, have 
been discovered in the Pacific Ocean and other seas. The naturalist 
Forster, who accompanied Cook in his voyage round the world, first 
made known the more remarkable characteristics of these wonderful 
formations. He perfectly comprehended their origin, which he was 
the first to attribute to the development of calcareous zoantharian 
polyps. 
After Forster, many other naturalists—Lamouroux, Chamisso, 
Quoy, Gaimard, Ehrenberg, Ellis, Darwin, and Dana—have furnished 
science with many precious memoirs on the natural history of coral 
islands and coral reefs. We can only glance at a few of the more 
remarkable facts connected with these interesting formations. 
The atolls present three unfailing and constant peculiarities. 
Sometimes they constitue a great circular chain, the centre of which 
is occupied by a deep basin, in direct communication with the ex- 
terior sea, through one or many breaches of great depth. These are 
the atod/s, described more than two centuries ago by Pyrard de Laval ; 
sometimes they surround, but at some distance, a small island, in 
such a manner as to constitute a sort of skeleton or girdle of reefs ; 
finally they may form the immediate edging or border of an island or 
continent. In this last case they are called fringing reefs. At the 
distance of a few hundred yards only from the edge of some of these 
reefs, the sea is of such a depth that the sounding-lead has failed to 
reach the bottom. 
