288 FLORIDA STATE GEOLOGICAL SURVEY. 
* 4 & 
origin in what is now the plateau region of northeast Alachua County. 
The soluble Vicksburg limestone underlying this section was removed 
by solution more rapidly than the less soluble rocks to the ea^t with 
the result that the basin has now been lowered to a level of about sixty 
feet which is equal to or below that of the former outlet through Or¬ 
ange Lake, and the drainage now passes off through sinks. When 
the sink is clogged the prairie becomes a lake. Under extremely heavy 
rainfall the lake would probably rise to a level permitting escape 
through its former outlet. 
NOTES ON FULLERS EARTH. 
The occurrence of fullers earth in the Devil’s Millhopper, six 
miles northwest of Gainesville, in Alachua County, was noted by 
Vaughan as early as 1901. 1 The following section measured with a 
hand level was made at this place. The top of this section as shown 
by the topographic map is about 180 feet above sea. 
Section at the Devil’s Millhopper. 
7. Covered and sloping .. 25 feet. 
6. Yellowish phosphatic limestone . 15 feet. 
5. Bluish-green sandy marl . 8 feet. 
4. Gray and blue sands and impure fullers earth. 40 feet. 
3. Yellowish limestone .. 1354 feet. 
2. Sandstone ..... 454 feet. 
1. Whitish limestone, weathering yellow . 5 feet. 
Ill 
At the city pumping plant two and a half miles southeast of 
Gainesville, fullers earth was also observed. The fullers earth here 
is associated with a calcareous sandstone. 
MARION COUNTY. 
Marion County, in central peninsular Florida, has a total area of 
1,610 square miles. The greater part of the county is characterized 
by a rolling surface with low rounded hills. The western half of the 
county has few or no surface streams, the surface sands and sandy 
clays permitting the water to pass directly into the limestone beneath, 
thus supplying the large springs of this county. Rock phosphate occurs 
extensively in the western part of Marion County. The rounded hills 
of the interior of the county reach an elevation of from 100 to 150 
feet and in some instances to 200 feet. 
U. S. Geol. Surv. Min. Res., 1901, p. 932, 1902. 
