314 rR()CKKI)IXG8 OF THK ACADEMY OF [1890. 



definite data rei^ardiiig the condition of the surface upon which 

 those structures are reared. The position San Juan de Uh'ia, on 

 the Gallega Reef, is evidence that there have been no changes of 

 level of any consequence for at least 800 years, or since the year 

 (1582) when the construction of the fort was first begun ; the recent 

 development of the reefs has been in a stable area. 



Manifestly, in a region of stability there could have been no 

 " atolls of subsidence" formed, and we find no I'eefs that can even 

 remotely be associated Avith the atoll structure. The facts thus far 

 neither favor nor oppose the Darwinian theory of coral formations, 

 but they are fully in consonance with it ; and, so far as I see, they 

 neither favor nor absolutely disprove the substitute theory which 

 has been advanced by Mr. Murray and his followers. It is, how- 

 ever, a significant (if perhaps not remarkable) circumstance that 

 with peripheral acceleration (in growth ) and internal solution — the 

 two determining conditions of atoll formation of most of the adher- 

 ents of the new school — we should still fail to find in a region of 

 stability, atoll-reefs. It is true that, with the very slow rate of solu- 

 tion which has been assumed to be possible, a well or lagoon of any 

 depth could barely be formed in a period of three hundred years ; 



somewhat singular paper on " The Topography of Florida" — singular for reason 

 of its failing to take account of the geological work done in the State prior to his 

 own researches — supplements my proof of the geologically recent uplift of the 

 southern portion of the Floridian peninsula with testimony bearing directly upon 

 the reefs themselves : thus the reef of Biscayne Bay " gives proof of a recent eleva- 

 tion of the shore to the height of about twenty-five feet " (Bull. Mus. Comp. Zool., 

 XVI, 1890, p. 143). This statement is, of course, directly antagonistic to the posi- 

 tion held by Mr. Agassiz. In my description of the rocks of Sarasota Bay, west 

 coast of Florida (Trans. Wagner Free Inst. Science, 1, 1887, p. 15), I state that 

 it is " more than probable that this portion of the coast has quite recently been 

 undergoing subsidence" ; Prof Shaler {Op. cit., p. 148) corroborates this position 

 by the statement : " There is a good deal of evidence to the effect that the whole 

 peninsula of Florida has undergone a subsidence often or twenty feet in altitude 

 since the last period of elevation." 



With direct evidence thus in favor of both elevation and subsidence of the Flor- 

 idian region during the existing period of coral-growth, nothing remains of the as- 

 sumption that the formation of the Florida Reefs is in any way opposed to the 

 Darwinian theory of reef structure, for it absolutely nullifies the three leading 

 propositions that are embodied in that assumption : 1. That there has been no sub- 

 sidence in the coral makmg tract ; 2, that there has been no elevation in the same 

 region; and 3, that great banks, organically constructed, have been built up with- 

 out assisting movements of the crust. The same argument applies to the reefs of 

 the Yucatan bank. 



