Davis — DancCs Confirmation of Darwin's Theory. 173 



Art. XYIII. — Dana's Confirmation of Darwin's Theory of 

 Coral Beefs ; by W. M. Davis. 



James Dwight Dana, born four years to a day after Darwin 

 on February 12, 1813, naturalist of the United States Exploring 

 Expedition under Wilkes from 1838 to 1842, and afterwards 

 until his death in 1895 professor of geology at Yale University, 

 was for over half a century a leading figure among American 

 men of science. On the hundredth anniversary of his birth, it 

 is fitting to call attention to a contribution that he made many 

 years ago to Darwin's theory of coral reefs, a contribution which 

 has long been overlooked although it supplies the most impor- 

 tant confirmatory evidence of the truth of the theory that has 

 ever been brought forward, and at the same time points the 

 way to demonstrate the insufficiency of certain other theories. 

 Dana's contribution consists in his having considered more fully 

 than Darwin did, the changes that must take place in the shore 

 line of the subsiding central island while barrier reefs are 

 developing around it. 



Darwin most ingeniously invented the theory of subsidence 

 while he was in South America (in 1835?), before he had seen 

 a true coral reef ; he had afterwards only to test the theory by 

 comparing its already deduced consequences with the facts that 

 he observed during the voyage of the " Beagle " across the 

 Pacific and Indian oceans, and with the records of other 

 observant voyagers which he studied carefully after his return 

 to England. The theory bore this test admirably ; it explained 

 the things that it was made to explain, and brought into 

 reasonable relationship a large variety of facts that had pre- 

 viously seemed to be arbitrarily distributed. It was therefore 

 regarded as "true" by its inventor; but apart from certain 

 correlations of coral reefs with areas of recent uplift and with 

 active and extinct volcanoes — correlations which appear to be 

 less assured now than seventy years ago — the subsidence theory 

 did not gain that increased probability of correctness which 

 comes from the capacity to explain facts that were unknown 

 or unnoticed at the time of its invention. Nevertheless, for 

 forty years the scientific world accepted it as demonstrated. 

 Darwin's diagrams of a subsiding island and an upgrowing 

 reef have been reproduced over and over again on countless 

 blackboards, as representing one of the great discoveries of 

 geological science. 



The introduction of other theories of coral reefs during the 

 last thirty years is familiar matter. Mention will here be 



