164 FLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT

 The Tallahassee Pressed Brick Company, Havana, located farther up the Ocklocknee River, also utilizes a flood-plain clay having properties very similar to the clay previously described. This plant is located on the Georgia, Florida and Alabama Railroad. The deposit is about five feet thick, overlain by about six inches of soil, and has been proven on about sixty acres. It probably underlies a more extensive area.
 This clay has excellent working qualities. A good grade of common building brick, fireproofing, hollow blocks, or drain tile may be made from it. Its physical properties are: Physical Properties of the Tallahassee Pressed Brick Company Clay (Lab. No. o-17).
 Plasticity, judged by feel............ Excellent.
 W ater of plasticity................. 25.65%
 Linear air shrinkage................ 10.3 %
 Volume air shrinkage............... 27.8 %
 Modulus of rupture, average........ 498.4 pounds per square inch.
 Slaking test ....................... 48 hours.
 Steel hard at cone 010.
 Fire tests:
 Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 0.3 17.32 33.00 Brick red.
 1050 0.3 16.80 32.45 Brick Red.
 1150 0.7 14.20 30.25 Brick Red.
 1190 0.7 11.42 25.50 Brick Red.
 1230 1.2 11.05 29.20 Brick Red.
 1310 1.8 10.90' 23.75 Brick red.
 1370 2.2 10.18 20.20 Brown.
 1430 2.2 9.30 14.20 Brown.

 The two plants located on the Ocklocknee River supply a demand for brick throughout northwestern Florida and southern Georgia.


 GLADES COUNTY

 Glades County borders Lake Okeechobee on the west and is underlain chiefly by sands and marls in which exposures are rare. No clays of importance are known.
 HAMIITON COUNTY

 Hamilton County is located in north Florida between the Suwannee and Withlacoochee rivers. The surface materials are chiefly Chattahoochee, Alum Bluff and Recent formations, in which surface, sandy clays, in places containing some gravel, are common.