FLORIDA REEFS. 57 
united to the main-land by the complete filling up and consolidation of 
the channel which once divided it from the extremity of the peninsula, as 
a channel iu)w separates the keys from the shore-blufis, and the outer reef, 
again, fiom the keys. These three concentric reefs, then, — the outer reef, 
the keys, and the shore-bluffs, — if we measure, the growth of the two latter 
on the same low estimate by which I have calculated the rate of 2)rogress of 
the former, cannot have reached their present condition in less than twenty 
thousand years. Their growth must have been successive, since, as we have 
seen, all corals need the fresh action of the open sea upon them, and if 
either of the outer reefs liad begun to grow before the completion of the 
inner one, it would have effectually checked the growth of the latter. The 
absence of an incipient reef outside of the outer reef shows these conclu- 
sions to be well founded. The islands capping these three reefs do not ex- 
ceed in height the level to which the fragments accumulated upon their 
summits may have been thrown by the heaviest storms. The highest hills 
of this part of Florida are not over ten or twelve feet above the level of the 
sea, and yet the luxuriant vegetation Avith which they are covered gives 
them an imposing appearance, recalling the islands of the Pacific. 
But this is not the end of the story. Travelling inland from the shore- 
bluffs, we cross a low, flat expanse of land, the Indian hunting-ground, which 
brings us to a row of elevations called the Hummocks. This hunting-ground, 
or Everglade as it is also called, is an old channel, changed first to mud-flats 
and then to dry land b}' the same kind of accumulation that is filling up 
the present channels, and the row of hummocks is but an old coral reef 
with tlie keys or islands of past days upon its summit. Seven such reefs 
and channels of former times have already been traced between the shore- 
blufis and Lake Okee-cho-bee, adding some fifty thousand years to our pre- 
vious estimate. Indeed, upon the lowest calculation, based upon the facts 
thus far ascertained as to their growth, we cannot suppose that less than 
seventy thousand years have elapsed since the coral reefs ahead}- known to 
exist in Florida began to grow. 
When we remember that this is but a small portion of the peninsula, and 
that, though we have no very accurate information as to the nature of its 
interior, yet the facts already ascertained in the northern part of the State 
formed, like its southern extremity, of coral growth, justify the inference 
that the whole peninsula is formed of successive concentric reefs, we must 
believe that hundreds of thousands of years have elapsed since its formation 
