CORAL-REEFS. 155 



Sea, and within some parts of the East Indian Archipelago 

 (if the imperfect charts of the latter can be trusted), there 

 are many scattered reefs, of small size, represented in the 

 chart by mere dots, which rise out of deep water : these 

 cannot be arranged under either of the three classes : in 

 the Red Sea, however, some of these little reefs, from their 

 position, seem once to have formed parts of a continuous 

 barrier. There exist, also, scattered in the open ocean, 

 some linear and irregularly formed strips of coral-reef, 

 which, as shown in the last chapter, are probably allied in 

 their origin to atolls ; but as they do not belong to that 

 class, they have not been coloured ; they are very few in 

 number and of insignificant dimensions. Lastly, some 

 reefs are left uncoloured from the want of information 

 respecting them, and some because they are of an inter- 

 mediate structure between the barrier and fringing classes. 

 The value of the map is lessened, in proportion to the 

 number of reefs which I have been obliged to leave 

 uncoloured, although, in a theoretical point of view, few 

 of them present any great difficulty : but their number 

 is not very great, as will be found by comparing the map 

 with the statements in the Appendix. I have experienced 



Phys. Atlas, 1840, No. 7 of Geological Part, a volcano on the 

 coast of Pondicherry is said to have burst forth in 1757. Ordin 

 aire {Hist. Nat. des Vo leans, p. 218) says that there is one at 

 the mouth of the Persian Gulf, but I have not coloured it, as 

 he gives no particulars. A volcano in Amsterdam, or St, Paul's, 

 in the southern part of the Indian Ocean, has been seen {Naut. Mag., 

 1838, p. 842) in action. Dr. J. Allan, of Forres, informs me in a 

 letter, that when he was at Joanna, he saw at night flames apparently 

 volcanic, issuing from the chief Comoro Island, and that the Arabs 

 assured him that they were volcanic, adding that the volcano burned 

 more during the wet season. I have marked this as a volcano, though 

 with some hesitation, on account of the possibility of the flame arising 

 from gaseous sources. 



