402 CORAL AND CORAL REEFS 



great masses. They differ from the ordinary polypes 

 just in the same way as those plants which form a peat-bog 

 or meadow-turf dift'er from ordinary plants. They have a 

 habit of growing together in masses in the same place ; 

 they are what we call " gregarious " things ; and the 

 consequence of this is, that as they die and leave their 

 skeletons, those skeletons form a considerable solid aggre- 

 gation at the bottom of the sea, and other polypes perch 

 upon them, and begin building upon them, and so by 

 degrees a great mass is formed. And just as we know 

 there are some ancient cities in which you have a British 

 city, and over that the foundations of a Roman city ; and 

 over that a Saxon city, and over that again a modern city, 

 so in these localities of which I am speaking, you have the 

 accumulations of the foundations of the houses, if I may 

 use the term, of nation after nation of these coral polypes ; 

 and these accumulations may cover a very considerable 

 space, and may rise in the course of time from the bottom 

 to the surface of the sea. 



Mariners have a name which they apply to all sorts of 

 obstacles consisting of hard and rocky matter which comes 

 in their way in the course of their navigation ; they call 

 such obstacles " reefs," and they have long been in the 

 habit of calling the particular kind of reef, which is formed 

 by the accumulation of the skeletons of dead corals, by the 

 name of " coral reefs," therefore, those parts of the world 

 in which these accumulations occur have been termed by 

 them " coral reef areas," or regions in which coral reefs 

 are found. There is a very notable example of a simple 

 coral reef about the island of Mauritius, which I dare say 

 you all know, lies in the middle of the Indian Ocean. It 

 is a very considerable and beautiful island, and is sur- 

 rounded on all sides by a mass of coral, which has been 

 formed in the way I have described ; so that if you could 

 get upon the top of one of the peaks of the island, and look 

 down upon the Indian Ocean, you would see that the 

 beach round the Island was continued outward by a kind 

 of shallow terrace, which is covered by the sea, and where 

 the sea is quite shallow ; and at a distance varying from 

 three-quarters of a mile to a mile and a half from the 

 proper beach, you would see a line of foam or surf which 

 looks most beautiful in contrast with the bright green 

 water in the inside, and the deep blue of the sea beyond. 

 That line of surf indicates the point at which the waters 



