FLOEIDA EEEFS. 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 



