32 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
raphy. The Miami Limestone forms a partial exception. This for 
mation over a small area in Dade County lies at an elevation of 
from 9 to 15 feet above sea. The top surface of this limestone is ex 
ceedingly rough, owing to differential solution. A small amount of 
loose sand lies on the surface which tends to fill up the irregularities 
in the limestone. The limestone is cavernous, and occasional sinks 
or openings to the underground cavities occur. The area affected by 
the Miami Limestone extends from near the north line in Dade 
County to some miles below Homestead, being broadest at Home 
stead. Cuban pine is the prevailing forest tree over this area. Saw 
palmetto is the chief undergrowth. 
The Keys between Miami and Key West, the foundation of which 
is limestone, rise but a few feet above sea level. The coquina lime 
stone which lies along the Atlantic Coast, together with local marls, 
gives rise to the long strip of calcareous hammock land that occurs 
along the Atlantic Coast south of St. Augustine. 
NON-LIMESTONE SECTION. 
In the non-limestone sections of the State erosion has been 
chiefly mechanical by normal stream action, and the physiographic 
types are determined largely by the drainage conditions. Near some 
of the larger rivers surface drainage by lateral streams has been 
fully developed. This is true of the Apalachicola Eiver, especially 
along its east side, where the rise in elevation to the plateau level 
is rapid, a narrow strip along the western border of Gadsden County 
being thoroughly drained by the numerous small tributaries to this 
river. The central part of this county is also well drained by the 
tributaries to Little Eiver. The northern parts of Escambia and 
Santa Eosa Counties include areas well drained by streams tribu¬ 
tary to the Perdido, Escambia and Black Eivers. On the other hand 
there are areas that are swampy owing to the fact that surface 
streams have not yet developed sufficiently to afford drainage. The 
large area of southern Florida known as the Everglades is of this 
type. The Everglades, as previously stated, probably date from the 
close of the Pleistocene period, and since that time numerous small 
streams have been cutting their way back from the coast. Among 
these are New Eiver, Hillsboro Eiver, Miami Eiver, and some 
smaller creeks flowing into the Atlantic, and North Eiver, Harney 
Eiver, Lostmans Eiver, and many smaller creeks, flowing into the 
Gulf from the southern end of the Everglades; and the Caloosa 
hatchee Eiver, which flows west from Lake Okeechobee. Ultimately 
by the action of these streams the ’Glades would be drained. The 
