FLORIDA REEFS. 39 



Changes in Ages to come. 



Among the questions contained in your instructions, you ask whether the 

 growth of coral reefs can be prevented, or the results remedied, which are 

 so unfavorable to the safety of navigation. I may say that here, as in most 

 cases where the operations of nature interfere with the designs of man, it is 

 not by a direct intervention on our part that we may remedy the difficul- 

 ties, but rather by a precise knowledge of their causes, which may enable 

 us, if not to check, at least to avoid the evil consequences. I do not see the 

 possibility of limiting in any way the extraordinary increase of corals, be- 

 yond the bounds which nature itself has assigned to their growth. We 

 have seen how successfully several reefs have been formed, more or less 

 parallel, within the limits of the peninsula of Florida, as well as beyond 

 the main-land. We have seen, also, how these parallel or concentric reefs 

 have been gradually transformed into main-land by the accumulation of 

 coral sand and mud with other loose materials, and also that the keys are 

 now slowly annexed to the main-land, by the same process. We may, there- 

 fore, safely infer that, as far as the conditions exist for the formation of simi- 

 lar accumulations of loose materials, they will continue to occur, but they 

 will never extend beyond the natural foundation from which a coral reef 

 may rise ; and as we now have sufficient evidence that this foundation is 

 a sea-bottom, under from twelve to twenty fathoms, we may be satisfied 

 that outside of the present outer reef, where the slope is steep, sinking 

 rapidly to unfathomable depths, there is no opportunity for the growth of 

 a new reef. 



Here and there the reef may widen somewhat, towards the Gulf Stream, 

 within those limits at which the depth does not exceed twenty fathoms ; 

 and from the knowledge we already possess of the soundings outside the 

 reef we know positively that this is nowhere a broad stream. We may 

 therefore rest assured that the changes which are going on will chiefly 

 consist in bringing up the reef, for its whole extent, to the surface of the 

 water, with occasional intervening channels kept open by the currents, such 

 as exist now between the keys ; that this reef once matured, will be covered 

 by coral debris, becoming transformed into a range of keys, similar to that 

 which exists now inside of it ; that the depth of the ship-channel between 

 the reef and the main range of keys will gradually lessen, and the channel 

 itself be changed into mud flats, similar to those stretching now between 



