OCKLOCKNEE AND AUCILLA RIVERS. 
99 
ANALYSIS OF LIMESTONE ROCK FROM LAKE IAMONIA. 
Moisture —----_,_____ .33% 
Insoluble matter _____ a_____4.67% 
Calcium oxide 53.20% equivalent to calcium carbonate_95.00% 
This limestone underlies the whole area of these three counties. 
It has, however, a slow dip to the south which carries it beneath the 
surface in the southwestern part of Leon County and in the western 
part of Wakulla County, although in the eastern part of Wakulla 
County, it remains at the surface to the Gulf of Mexico. 
The Ocklocknee River, which forms the western boundary of 
Leon and Wakulla counties, flows on this formation from the State 
line to somewhat below the crossing of the Seaboard Air Line Rail¬ 
road, a distance in a direct line of approximately 20 miles. At the 
crossing of the Seaboard Air Line Railroad the Ocklocknee River 
turns in a direction west of southwest. Had the river continued 
south from the station Ocklocknee, it would have remained on or 
practically on the limestone to the Gulf. Its south westward course, 
however, carries it onto formations of later age. In other words, 
the Chattahoochee limestone dips beneath the bed of the river, the 
dip of the rock to the south being greater than the gradient, or fall 
of the stream, when deflected as it is to the southwest. 
The St. Marks River and its tributaries form an indefinite drain¬ 
age system crossing the area in a general north-south direction. 
This stream flows practically on the limestone throughout its whole 
course to the Gulf, and is in part a surface stream and in part sub¬ 
terranean. The history of the development of this drainage system 
will be described subsequently. Between the Ocklocknee River on 
the west and the Aucilla River on the east there are practically no 
surface streams, as the limestone is sufficiently near the surface to 
receive the drainage. A partial exception is afforded by the 
Wakulla River, which emerges from its subterranean course to form 
the great Wakulla Spring. The Sopchoppy River, another excep¬ 
tion to the general rule of absence of streams, is in the southwestern 
part of the area where the limestone has dipped beneath the surface. 
The Aucilla River flows near the top surface of this limestone from 
the State line to the Gulf. 
Throughout practically the whole of Leon County, and a part 
of Jefferson and Wakulla Counties, the Chattahoochee limestone 
lies buried beneath the Alum Bluff sands and clays, and it is only 
