AGASSIZ : BAHAMAS. 183 



circumstances favor. . , . They are not evidence against the subsidence 

 theory, but simply local examples under the general principle just stated." 

 It seems to me that in the first part of the passage quoted Professor 

 Dana grants the principal factors which -have been advanced iu opposition 

 to the universal application of the Darwinian theory of coral reefs. The 

 objections to it from this and that quarter have little by little circum- 

 scribed the area within which it is applicable. It is not applicable to 

 the West Indian and Caribbean Sea reefs. It does not hold true for 

 the Bahamas or Bermudas any more than for Cuba or Florida. It 

 does not hold for the Sandwich Islands or the Galapagos. It has not 

 been accepted by Semper, by Rein, by Murray, by Bourne, by Guppy, 

 nor by others who have in recent years examined many of the localities 

 which are considered by Dana and Darwin as typical of the subsidence 

 theory. 



Perhaps one of the best sections of coral reef rock and limestone is 

 that given by Julien, 1 as far back as 1867, in his description of the 

 geology of Sombrero, W. I. The beds examined by him vary in thick- 

 ness between thirty-three and sixty-six feet. From his description of 

 the key as an atoll I imagine it must resemble either Hogsty Iteef or 

 some of the smaller pseudo-atoll banks of the Bahamas, only it has been 

 elevated about forty feet. Some of the beds are separated by a thin 

 layer of limestone differing from the preceding. 



The formation of hills of nearly four hundred feet in height, in a dis- 

 trict showing a probable subsidence of at least two hundred and fifty or 

 three hundred feet, shows very plainly how a limestone bed of that thick- 

 ness may have been formed from a coral reef flourishing at the time when 

 the beach which bordered the seolian islands was at least two hundred feet 

 higher than the present beaches on the Bahamas. It is not probable that 

 during the period of subsidence the reef kept up its growth with sufficient 

 vigor to add to the material which helped to build the seolian hills now 

 i disappearing before the action of the sea. On the contrary, we can only 

 imagine such high aeolian hills as those of the Bahamas to have been 

 formed in a period of rest, during which the great beach of the then 

 existing reef constantly supplied fresh material to be changed by the 

 surf and the winds into sand for the heaping up of sand dunes. They 

 could not be formed in a district of subsidence unless the subsidence 

 was slower than the rate of growth of the corals, which is not the case 

 in the Bahamas, as the reefs of to-day, even when they come to the sur- 



1 On the Geology of the Key of Sombrero, W. I , by Alexis A. Julien, Ann. Lye. 

 of Nat Hist, of New York, Vol. VIII. p. 251. 



