274 ANNUAL OF SCIENTIFIC DISCOVERY. 



it would be impossible to select, with confidence, any sites for light- 

 houses, buoys, beacons, c. Prof. Agassiz, as the result of his exam- 

 ination, declared his full conviction was that no other reef ivould ever be 

 so formed. He then stated that he believed there had taken place no 

 elevation in the region, as most have supposed. He had examined the 

 upland keys carefully, and he found that, in all, the coral formation did 

 not extend above water mark. From the main land a flat had extended 

 off into the sea, and, at the proper depths, these little animals had com- 

 menced the inner reef, which gradually rose to the surface. Upon this 

 reef, in many places, fragments of coral, and sand in layers, had been 

 driven by the action of winds and waves, so that these islands were 

 several feet above the water ; but, in no instance, does the living coral 

 formation exist above the present sea limit. Hence there had been 

 no elevation, but all the elevation had been caused in this manner. 

 Between this reef and the main land the basin which had been formed 

 by the reef gradually filled up and formed the shallow mud flats. Be- 

 yond this reef the sand had been washed up, and the flat had been 

 raised, until the conditions necessary for the existence of the polypi 

 were obtained, when the outer reef was commenced and raised to the 

 water level, for the polypi cannot work above the water. This reef 

 would undoubtedly be increased laterally, and sand and detritus be 

 washed upon it, forming a series of keys like the inner reef, but no reef 

 would be formed beyond, because this reef was reared on the extreme 

 limit of the flat, and outside this reef the shore was precipitous and deep 

 into the channel of the Gulf Stream, and hence the conditions for the 

 formation of another reef could never exist. It was only necessary, then, 

 to build lighthouses on this outer reef, and the coast was as safe as any 

 coast, for there were abundant entrances within the outer reef where 

 a vessel would ride in safety. The water was yet deep between the 

 two reefs ; but, as the lights are now placed, they rather allured the 

 vessel on to the outer reef than warned them of danger, and, he thought, 

 had been erected according to the suggestions of the wreckers. 



The formation of the so-called " Everglades " is described as follows : 

 " This portion of the peninsula is only a vast coral bank, composed 

 of a series of more or less parallel coral reefs, which have successively 

 grown from the bottom of the sea up to the surface, and have been 

 added to the main land by the gradual filling of the intervals which 

 separate them, with deposits of coralline sand and debris, brought 

 thither by the action of the tides and of the currents. On the solid 

 reefs, the action of the waves accumulates masses of sand and mud the 

 height of twelve feet above the sea level. This soil soon becomes fixed 

 by the growth of mangrove trees and other plants. The intervals, 

 being lower, form large fresh water swamps, filled with every kind of 

 aquatic plant, through which the Seminole, like the white man, can 

 penetrate only in a boat. The higher and drier reefs are the so-called 

 hammocks, which rise like islands from the deep and green swamps 

 that bear the name of everglades. This formation still goes on. The 

 series of keys, as they are called, which border the southern and east- 

 ern coast, and terminate with the Tortugas Islands, far beyond the point 

 of Florida, are only a new line of hammocks which will soon be united 

 to the main land by everglades formed by the deposits of the sea." 



