56 On the Gulf Stream and the Keys of Florida. 
YY e Gi 
Mis . & 
MMM eas deren! 
et 
ta 4 
Fig. 5 is an ideal section showing the su hanges which would occur on 
such a supposition, The letters represent isn potae ane as in figs. 2, 3, and 4. 
Inspection of fig. ome soi! that this has actually been the case : 
at least ca pe last t reefs. | 
We have chosen oe trace this process only as far as the north- 2 | 
ern shore of the everglades, because thus far we have the most ey 
putable evidence of the recency of the formation. But in 
the same manner we might carry it still farther back in time and 
ward in space, and represent the successive reefs by which 
the aaneeenes portion of the rest of the peninsula was formed. f 
There is one other fact of great importance, and otherwise in- | 
eEpua le, which receives a ready explanation upon this ery, 
which I think, therefore, is sthapaly aon confirmatory of its trut 
I allude to the fact that the successive reefs are found at some 
distance xy one another; in other words that the peninsula is 
form: a succession of barrier reefs, instead of a continuous ‘ 
a ae growth of fringing reef. The reefs of Florida are in ‘ 
some respects entirely peculiar. Barrier reefs have heretofore 
been considered as always the result of subsidences of the sea 
bottom, and are invariably looked on as the sign of such subsi- # 
dence. But in Florida we have barrier reefs where it is certain 
there has been no subsidence. e have here, therefore, a — 
was 
which he has alluded to the fact, nor as far as I know, has he 
ever attempted or even thought of a probable explanation. The : 
explanation which I would offer is as follows :— ae | 
t is a well known condition of coral growth that the sea i 
water must be pure and transparent. Corals will not grow, 
therefore, on mudd aborts, or in water upon the bottom of 
which sediment is deposited, Now, j ; 
that while the Gulf Raia bears sediment in its deeper strata, 
it is superficially transparent, and we have already shown that 
