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 srrowth 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 way 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 justify 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, which 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 j^ear 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 bj"- 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. In 1841 the water rose ten" feet above high-Avater 
mark at Cape Romaine, on the western shore of the peninsula. 
These facts suffice to show thiit 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. 
