36 FLORIDA REEFS. 



least deranging the level of the latter. We must suppose this to be true for 

 the main bluffs also, and for all the concentric ranges of hummocks and 

 swamps lying within them. To suppose that in each instance these up- 

 heavals were strictly limited to one such narrow belt would be contrary to 

 all our knowledge of such agencies. To suppose all the upheavals to have 

 been simultaneous would be equally opposed to what we know of the mode 

 of growth of coral reefs. Their formation must be successive, since the 

 outer one cannot start till the completion of the previous one furnishes the 

 necessary conditions for its foundation. 



There is in reality but one waj^ of accounting for this equality of level 

 in the successive reefs; which is, to suppose that their loftiest ridges 

 are the maximum height at which materials can be accumulated by the 

 natural agency of gales, and we have sufficient evidence to jvistify the adop- 

 tion of this view. 



The fact that, at present, the highest tides, during the most severe gales, 

 do not reach the level of the bluff summits along the shores of the main- 

 land, or even that of the maximum height of Key Largo or Key West, does 

 not invalidate this supposition, for when the shore bluffs of the main-land 

 were formed, the ocean had full sweep over the ground now occupied by the 

 reef and mud flats, Avhich did not then exist ; and when Key Largo and 

 Key West attained their maximum height, the outer reef did not yet form 

 a barrier, checking the violence of the Gulf Stream in that direction. But, 

 even with the present obstruction, we have evidence of the occasional rise 

 of the water to heights which fully justify our assumption that even the 

 highest ridges on the shores of the main-land and on the reef have been 

 formed by the action of severe gales. For, in the year 1846, the water rose 

 eight and a half feet above high-water mark at Key Vacas. Key West was 

 entirely inundated during the same gale ; and though that island is some- 

 what protected by the reef, even at present, the rushes, driven upon it by 

 the flood, may be seen among the trees and bushes, at a height almost equal 

 to its loftiest summit. Li 1841 the water rose ten feet above high-water 

 mark at Cape Romaine, on the western shore of the peninsula. 



These facts suffice to show that the explanation we have given of the for- 

 mation of the reef is in accordance with the powers of the agencies to 

 which it is ascribed, and, when taken in connection with the peculiar 

 arrangement of the materials of which they consist, seems to us to prove the 

 justness of this view. 



