No. 2 — The Florida Elevated Reef. By ALEXANDER AGASSIZ. 
With Notes on the Geology of Southern Florida. Ву LEON 
S. GRISWOLD, 
The Florida Elevated Reef. By ALEXANDER AGASSIZ. 
(Plates I. to XVII.) 
I was anxious to examine again the Florida reefs in the light of the 
experience gained by my visit to the Bahamas and Bermudas; and as 
was anticipated, my ideas of the mode of formation of the Keys have 
been materially changed, and I no longer consider the Marquesas as a 
true atoll." After having seen at the Bermudas the mode of formation 
of the sounds, I have become satisfied that the Marquesas are a sound. 
But the Marquesas Sound, as well as other Florida sounds, does not, I 
think, owe its origin to subsidence, but merely to the mechanical and 
solvent action of the sea. It is interesting to trace on the large scale 
charts of the Coast Survey (Nos. 167-169) the mode of formation of 
Key Biscayne Bay, composed of two sounds, followed by Barnes Sound, 
and finally to the westward, by the Bay of Florida, itself only a series 
of disconnected sounds indicated by isolated keys and bars. The same 
disintegration is going on at the Pine Islands, Key West, Boca Chica, 
Boca Grande, Ballast Key, and is especially well seen in Key Largo and 
the Marguesas, to the west of the principal line of keys, being a remark- 
ably well preserved sound of an elliptical shape. 
To my great surprise I found that Lower Mateeumbe was edged by 
an elevated reef about two feet above high-water mark, and this ele- 
vated reef I was able to trace all along the shores of the keys to the 
east of Indian Key as far as Soldier Key, off the central part of Key 
Biscayne Вау. I examined this elevated тес? also at Indian Key where 
its highest point is eight feet above high-water mark, at several points 
on Key Largo, Old Rhodes, Elliott Key, and, as the most easterly point, 
Soldier Key. No trace of this elevated reef could be detected north 
1 See Note on the Florida Reef, by A. Agassiz. (Letter to J. D. Dana dated 
Tampa Bay, Florida, December 27, 1804. From the American Journal of Science, 
Vol. XLIX., February, 1895, 
VOL. XXVIII, — NO, 2. 1 
