CORAL-REEFS. 



INTRODUCTION 



The object of this volume is to describe from my own 

 observation and the works of others, the principal kinds of 

 coral-reefs, more especially those occurring in the open 

 ocean, and to explain the origin of their peculiar forms. 

 I do not here treat of the polypifers, which construct these 

 vast works, except so far as relates to their distribution, 

 and to 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 'encircling 

 reefs,' and 'fringing 5 or 'shore -reefs.' The lagoon- 

 islands have received much the most attention; and it is 

 not surprising, for every one must be struck with astonish- 

 ment, when he first beholds one of these vast rings of 

 coral-rock, often many leagues in diameter, here and there 

 surmounted by a low verdant island with dazzling white 

 shores, bathed on the outside by the foaming breakers of 

 the ocean, and on the inside surrounding a calm expanse of 

 water, which from reflection, is of a bright but pale green 

 colour. The naturalist will feel this astonishment more 

 deeply after having examined the soft and almost gelatinous 

 bodies of these apparently insignificant creatures, and when 

 he knows that the solid reef increases only on the outer 

 edge, which day and night is lashed by the breakers of an 

 ocean never at rest. Well did Francois Pyrard de Laval, 



