FLOTIIDA REEFS. 39 
Changes in Af/es 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 
pai-allel, 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 
m.ay 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 ojiportunity 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 fiithoms ; 
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 
