THE 



STEUCTUEE AND DISTEIBUTION 



OF 



COEAL-EEEF8. 



INTRODUCTION". 



The object of this volume is to describe from my own 

 observation and the works of others, the principal 

 kinds of coral-reefs, and to explain the origin of their 

 peculiar forms. I shall not here treat of the poly- 

 pifers, which construct these vast works, except as 

 to their distribution, and the conditions favourable 

 to their vigorous growth. 



Without any distinct intention to classify coral- 

 reefs, most voyagers have spoken of them under the 

 following heads : ' lagoon-islands ' or ' atolls,' ' barrier ' 

 or c encircling reefs,' and ' fringing ' or ' shore reefs.' 

 The lagoon-islands have received much the most atten- 

 tion ; and it is not surprising, for every one must be 

 struck with astonishment, when he first beholds one of 



B 



