314 FORM OF A CORAL REEF. 



Although I have before had occasion to describe 

 some of the coral reefs as individual things, yet it 

 may facilitate the understanding them if I reca- 

 pitulate their most remarkable and striking pecu- 

 liarities. The size and form of an "individual coral 

 reef" is perfectly indeterminate ; it may be cir- 

 cular, oval, or linear ; its surface may vary from a 

 mere point to an area of many square miles. Those, 

 however, which occupy the extreme edge of a mass 

 of reefs, # or rise on one side from great depths, 

 having on the other comparatively shallow water, 

 have generally a linear form, being three, five or 

 ten miles long, and varying in breadth from one or 

 two hundred yards to perhaps a mile. This seems 

 more especially to be the case when their direction 

 runs across that of the prevailing wind. The 

 individual coral reefs which rise from an equal 

 depth all round, whether that depth be great or 

 small, are more commonly of an oval, circular, or 

 irregular shape, but these are usually much larger 

 when exposed to the wind and surf than in more 

 sheltered situations. 



To get an idea of the nature and structure of an 

 individual coral reef, let the reader fancy to himself 

 a great submarine mound of rock, composed of the 

 fragments and detritus of corals and shells, com- 



* There is a terra wanted to express the distinction between 

 an individual reef, unbroken by any deep water-channel, and a 

 group of such reefs. For the latter I am almost tempted to use 

 the word "reefery;" for the former I have, in this passage, used 

 the expression, " individual coral reef." 



