THE ORIGIN OF CORAL REEFS. 51 
PAR EN: 
THE ORIGIN OF CORAL REEFS. 
ee problem of the formation of coral reefs has, perhaps, 
attracted more general attention than it originally 
merited from the fact of its having excited the interest and 
employed the genius of Mr. Darwin. ‘The difficulties, how- 
ever, that attend their examination have until within the last 
seventy years prevented any serious attempts to mvestigate 
their structure; yet itis very remarkable that the explanation 
of atolls proposed by Chamisso, the naturalist who accom- 
panied Kotzebue, the Russian navigator, in his voyage to the 
South Sea in the years 1815—-1818,* is the very one towards 
which all recent observations are tending. ‘The larger and 
more massive species of corals, as this naturalist states, prefer 
the surf at the outer edge of the reef ; whilst the corals in the 
interior are hindered in their growth by the accumulation of 
shell and coral débris. In this manner the outer edge of a 
submerged reef first approaches the surface, and a ring of 
land enclosing a lake is subsequently formed from the 
materials piled up by the waves. Thus the atoll was pro- 
duced, in the opinion of Chamisso, by the natural growth of 
corals and by the action of the waves. Mr. Darwin himself 
supported this view of Chamisso, when he remarked that a 
reef growing ona detached bank would tend to assume an 
atoll structure. Some atolls in the West Indies had been 
probably formed, as he says, in this manner; but it was 
mainly the difficulty of assuming that there could be so many 
submerged coral banks in the Indian and Pacific Oceans that 
led him to reject the explanation of Chamisso as generally 
applicable to oceanic atolls. Mr. Darwin’s lack of evidence 
led him to his theory of subsidence. The researches, how- 
ever, of more recent years are leading us back to the original 
explanation of Chamisso, which Mr. Darwin, with our evidence 
before him, would have in the main accepted. 
I will pass over the theory of subsidence, supported though 
it was by Dana, Couthouy, and Beete Jukes, because the 
more recent facts concerning the ocean depths and the regions 
of living and upraised reefs compel us to regard it as no 
longer necessary, and I will pass to the consideration of the 
views advanced since the year 1850. In 1851 Professor 
Louis Agassiz, in his Report to the Superintendent of the 
* Kotzebues Voyage, 1815-18, vol. iii. p. 331. London, 1821. 
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