REVIEW OF THE GEOLOGY OF FLORIDA 
III 
DRAINAGE. 
The drainage conditions in Florida are in some respects excep¬ 
tional. In that part of the State in which limestones are near the 
surface, especially on the upland limestone section of the interior, 
the drainage is largely subterranean, although much of the water 
that thus enters the earth reappears through large springs, which 
supply streams. In the limestone belt the rainfall enters the earth 
either directly through the surface materials or through disappear¬ 
ing streams which discharge their flow into the porous rocks. The 
subterranean drainage is best developed in that part of the State 
known as the “lime sink” region, where, aside from the main 
rivers, there are few or no surface streams. Partial subterranean 
drainage, however, is characteristic of a very much larger area, 
and for the State as a whole, the average for surface run-off is 
low. 
The prevailingly level country over much of the State, together 
with porous soils, results in but limited surface wash. However, 
in the more hilly parts of the State the wash of roadbeds and soils 
under the influence of heavy rains is sometimes serious. 
The streams of Florida for the most part have a slight gradient 
and are slow moving. The drainage of the westward extension 
of the State is through numerous streams, of which the Apalachi¬ 
cola is the largest, having a general north-south direction. The 
drainage basins of the peninsula are for the most part ill-defined. 
The St. Johns River, which flows north, and the Kissimmee River, 
which flows south, receive much of the drainage of the Atlantic 
slope. Entering the Gulf of Mexico from the western slope of 
the peninsula are a number of streams, among which are the Su¬ 
wannee, Withlacoochee, Hillsboro and Caloosahatchee rivers. 
GEOLOGY 
Florida lies entirely within the Coastal Plains province, and the 
formations exposed at the surface are all of the Cenozoic period. 
The amount of limestone in Florida is relatively large; neverthe¬ 
less, a very considerable quantity of sedimentary material, includ¬ 
ing sand, clay and flint pebbles, was carried to the south and in¬ 
cluded in some of the Florida formations. The progress made in 
