86 CONDITIONS FAVOUKAIiLE TO Ch. IV. 



where the water is tranquil, and the heat intense. 

 This statement has passed from one geological work to 

 another ; nevertheless, the protection of the whole reef is 

 undoubtedly due to those kinds of coral, which cannot 

 even exist in the situations thought by these naturalists 

 to be most favourable to them. For should the outer 

 and living margin perish, of any one of the many low 

 coral-islands, round which a line of great breakers is 

 incessantly foaming, the whole, it is scarcely possible 

 to doubt, would be washed away and destroyed in less 

 than half a century. But the vital energies of the 

 corals conquer the mechanical power of the waves ; 

 and the large fragments of reef torn up by every 

 storm, are replaced by the slow but steady growth 

 of the innumerable polypifers which form the living 

 zone on its outer edge. 



From these facts, it is certain, that the strongest 

 and most massive corals nourish where most exposed. 

 The less perfect state of the reef of most atolls on the 

 leeward and less exposed side, compared with its state 

 to windward; and the analogous case of the greater 

 number of breaches on the near sides of those atolls 

 in the Maldiva Archipelago which afford some pro- 

 tection to each other, are obviously explained by this 

 circumstance. If the question had been, under what 

 conditions the greater number of species of coral, not 

 regarding their bulk and strength, were developed, I 

 should answer, — probably in the situations described 

 by MM. Quoy and Gaimard, where the water is 

 tranquil and the heat intense. The total number of 



