Ch. VI. DISTRIBUTION OF CORAL-REEFS. 161 



leave uncoloured ; but their number is not very great, 

 as will be seen by comparing the map with the state- 

 ments in the Appendix. I have experienced more 

 difficulty in colouring fringing-reefs than in colouring 

 barrier-reefs, as the former, from their small size, 

 have not much attracted the attention of navigators. 

 As I have had to seek my information from all kinds 

 of sources, I do not venture to hope that the map is 

 free from errors. Nevertheless, I trust it will give 

 an approximately correct view of the general distri- 

 bution of the coral-reefs throughout the world, (with 

 the exception of some fringing-reefs on the coast of 

 Brazil, not included within the limits of the map,) and 

 of their arrangement into the three great classes which, 

 though necessarily ill-defined from the nature of the 

 objects classified, have been adopted by most voyagers. 

 I may further remark, that the dark blue colour repre- 

 sents land entirely composed of coral-rock; the pale 

 blue, land with a wide and thick border of coral-rock ; 

 and the red, land with a mere narrow fringe of coral-rock. 

 Looking now at the map under a theoretical point 

 of view, the two blue tints signify that the foundations 

 of the reefs thus coloured have largely subsided, and 

 that the rate of subsidence has been less than the up- 

 ward growth of the corals. It is also probable that in 

 many cases the foundations are still subsiding. The red 

 signifies that the shores thus coloured support fringing- 

 reefs ; and they have not, as a general rule, recently 

 subsided, at least to any considerable amount, for the 

 effects of subsidence on a small scale would hardly be 



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