258 
FLORIDA STATE) GEOLOGICAL SURVEY. 
HILLSBORO COUNTY. 
LOCATION AND SURFACE FEATURES. 
Hillsboro County includes an area of 1,049 square miles. The 
county is crossed by the Atlantic Coast Line Railroad and by the 
Seaboard Air Line Railway, and their branches, and by the 
Tampa Northern Railroad. The elevation rises in passing inland 
from Tampa Bay and the Gulf. Plant City, near the east line 
of the county, is reported, by the Atlantic Coast Line Railroad, 
to be 137 feet above sea level. The level given by the Seaboard 
Air Line Railway for this locality is 125 feet above sea level. 
The elevation of other points in this county, along the Seaboard 
Air Line Railway, is as follows: Brandon, 74 feet; Knights, 
117 feet; Turkey Creek, 87 feet. The' elevation of points in this 
county, along the Atlantic Coast Line Railroad, is as follows: 
Hillsboro, 35 feet; Seffner, 74 feet, and Thonotosassa, 49 feet 
above sea. The Hillsboro and Alafia Rivers flow across this 
county and enter Hillsboro Bay. 
WATER-BEARING FORMATIONS. 
While no complete set of well drillings has been obtained, 
there is little doubt but that the deep wells of this county termi¬ 
nate in the Vicksburg Limestone. The surface exposures along 
Tampa Bay and along the Hillsboro River, for some miles above 
Tampa, are of the Tampa Limestone, Upper Oligocene, which 
overlies the Vicksburg formation or Lower Oligocene. A full 
description of the exposures of the Tampa formation in this 
county, by George C. Matson and F. G. Clapp, will be found in 
the Second Annual Report of this Survey, pages 84 to 91, 1909. 
AREA OF ARTESIAN FLOW. 
Flowing artesian wells are, probably, to be obtained entirely 
around Hillsboro and Tampa Bays. The head is sufficient to 
bring the water about ten to fifteen feet above sea level, and the 
wells will usually flow where the. rise above sea does not exceed 
this elevation. The accompanying’map shows the area in this 
county in which flowing wells can be obtained. 
