CORAL ISLANDS. I9I 



Struck with the appearance of certain islands, which presented a con- 

 formation akogether singular. In 1601, Pyrard de Laval, speaking 

 of the Malouine (now the Falkland) Islands, said : — " They are 

 divided into thirteen provinces, named atollons, which is so far a natural 

 division in that place, that each atoUon 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, beine 

 each about thirty leagues m 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 atolls, 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 tliey 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 atolls, 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. 



