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AGASSIZ: THE FLORIDA ELEVATED REEF. 87 
n such 
me 
peculiar knife-edge layers, running at all angles, so striking 
formations. 
Mr. Grisw 
old also suggests that oólitio rocks are formed in the bottom 
of the sounds. The oólitio sand and fragments of oölitie rock covering 
the bottom of the Florida sounds is derived from the disintegration of 
the æolian rock and of the reef rock which constitute the substratum 
and the highest parts of the keys, and from their extension inland 
(perhaps twenty to thirty miles) along the southern extremity of 
Florida from New River to Cape'Sable. This whole territory being, 
according to the determinations of Dr. E. O. Hovey, based upon an 
examination of the samples from the Key West Artesian well, underlain 
at a depth of about fifty foet, or less inland, by Pliocene rocks and at a 
depth of 700 feet by Eocene strata. 
Professor L. Agassiz, in his Report on the Florida reefs," mentions the 
existence of coral reefs in the interior of the mainland at a distance of 
about fivo miles from the mouth of the Miami River. Owing to the 
conclusions which he drew from the existence of this reef rogarding the 
probable mode of formation of a great part of the southern extremity 
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of Florida, his premises regarding the reef have been questioned. Pro- 
fessor Shaler has deseribed in detail a portion of the elevated reef 
which he found at some distance from the shore line. This leaves no 
doubt of the existence of an elevated coral reef of very great width, 
or of a succession of patches and flats covered by corals, The con- 
clusions drawn from the presence of this elevated reef by Professor 
| Agassiz regarding the structure of the greater part of the peninsula of 
Florida are thus seen to apply, though in a very modified sense, to à 
| comparatively narrow strip only of its southern extremity. Undoubtedly 
somo of the rotten honeycombed and pitted rocks which are observed 
all along the shore of the mainland from Cocoanut Grove to the mouth 
of the Miami River are composed of жоПап rock, the rock on the 
shore line being the remnant of an extended series of low wolian hills 
of which the traces can be found here and there in the stretch of shore 
| mentioned. In one locality a bluff of seolian rock fully twelve feet high 
(Plate XIX.) is still standing, and testifies to the existence of an ex- 
tended beach of coral sand derived from the wide stretches of now 
| elevated coral reef which undoubtedly flanked at one time the southern 
| shore lino of the peninsula of Florida, Parts of this broad reef belt 
| aro still visible to the southward as far as Bahia Honda and Sand Key, 
and it can be traced uninterruptedly, except where covered by sand 
1 U, S. Coast Survey Report for 1851; Mem. Mus. Comp. Zo, Vol. VII. No. 1. 
