FLORIDA RF.EPS. 53 
After a time, an immense quantity of such materials is formed about a 
coral reef Tides and storms constantly throw them up on its surface, and 
at last a soil collects on the top of the reef, wherever it has reached the 
surface of the water, formed chiefly of its own debris, of coral sand, coral 
fragments, even large masses of coral rock, mingled with the remains of the 
animals that have had their home about the reef, with sea-weeds, with mud 
from the neighboring land, and with the thousand loose substances always 
floating about in the vicinity of a coast, and thrown upon the rocks or shore 
with every wave that breaks against them. Add to this the presence of a 
lime-cement in the water, resulting from the decomposition of some of these 
materials, and we have all that is needed to make a very compact deposit 
and fertile soil, on which a vegetation may spring up, whenever seeds 
floating from the shore, or dropped by birds in their flight, take root on 
the newly-formed island 
Such caps of soil on the summit of a coral reef are of course very in- 
secure, till they are consolidated by a long period of accumulation, and 
they may even be swept completely away by a violent storm. It is not 
many years since the lighthouse, built on Sand Key for the greater security 
of navigation along the reef, was swept away, with the whole island on 
which it stood. Thanks to the admirably conducted investigations of 
the Coast Survey, this part of our seaboard, formerly so dangerous on 
account of the coral reefs, is now better understood, and every precaution 
has been taken to insure the safety of vessels sailing along the coast of 
Florida. 
I cannot deny myself the pleasure of paying a tribute here to the 
high scientific character of the distinguished superintendent of this survey, 
who has known so well how to combine the most important scientific aims 
with the most valuable practical results in his direction of it. If some have 
hitherto doubted the practical value of such researches, — and unhappily 
there are always those who estimate intellectual efforts only by their 
material results, — one would think that these doubts must be satisfied, now 
that the Coast Survey is seen to be the right arm of our navy. Most of the 
leaders in our late naval expeditions have been men trained in its service, 
and" familiar with all the harbors, with every bay and inlet of our southern 
coasts, from having been engaged in the extensive researches undertaken by 
Dr. Bache, and carried out under his guidance. Many even of the pilots of 
our southern fleets are men who have been employed upon this work, and 
