96 CORAL-REEFS. 



The inference, therefore, that one reef could not grow up 

 to the surface within a given time, because another, not 

 known to be covered with the same species of corals, and 

 not known to be placed under conditions exactly the same, 

 has not within the same time reached the surface, is 

 unsound. 



Section Second. 



On the rate of growth of coral-reefs. 



The remark made at the close of the last section, 

 naturally leads to this division of our subject, which 

 has not, I think, hitherto been considered under a right 

 point of view. Ehrenberg 1 has stated, that in the Red 

 Sea, the corals only coat other rocks in a layer from 

 one to two feet in thickness, or at most to a fathom and a 

 half; and he disbelieves that, in any case, they form, by 

 their own proper growth, great masses, stratum over 

 stratum. A nearly similar observation has been made by 

 MM. Quoy and Gaimard, 2 with respect to the thickness of 

 some upraised beds of coral, which they examined at Timor 

 and some other places. Ehrenberg 3 saw certain large 

 massive corals in the Red Sea, which he imagines to be of 

 such vast antiquity, that they might have been beheld by 

 Pharaoh ; and according to Mr. Lyell 4 there are certain 

 corals at Bermuda, which are known by tradition, to have 

 been living for centuries. To show how slowly coral-reefs 

 grow upwards, Captain Beechey 5 has adduced the case of 



1 Ehrenberg, as before cited, pp. 39, 46, and 50. 



2 Annates des Sciences Nat., torn. vi. p. 28. 



3 Ehrenberg, ut sup., p. 42. 



4 Lyell's Principles of Geology, book iii. chap, xviii. 



5 Beechey's Voyage to the Pacific, chap. viii. 



