A PRELIMINARY REPORT ON CLAYS OF FLORIDA 169

 Physical Properties of Brooksville Tampa Northern Clay (Lab. No. 0-21).
 Plasticity, judged by feel............ Excellent.
 W ater of plasticity................. 34.50%
 Linear air shrinkage................ 15.2 %
 Volume air shrinkage............... 41.2 %
 Modulus of rupture, average........ 147.0 pounds per square inch.
 Slaking test ....................... 3 minutes.
 Steel hard at cone 010.
 Overfires at cone 9.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 0.0 7.60 18.50 Salmon.
 1050 2.8 7.08 18.30 Brown.
 1150 3.8 6.88 16.20 Gray.
 1190 5.8 6.42 15.70 Gray.
 1230 3.8 5.82 10.10 Gray.

 A clay is exposed in the northeastern edge of Brooksville and vicinity which is unfitted for any kind of burned product. Its plasticity is very poor and its shrinkage is high. This clay warps badly, but is comparatively free from cracking. Its physical properties, which are given for the purpose of illustration, are:

 Physical Properties of Brooksville Clay (Lab. No. o-56).
 Plasticity, judged by feel............ Poor.
 W ater of plasticity................. 38.45%
 Pore water ........................ 4.90%
 Shrinkage water ................... 33.55%
 Linear air shrinkage................ 18.8 %
 Volume air shrinkage............... 35.8 %
 Modulus of rupture, average........ 218.0 pounds per square inch.
 Slaking test ....................... 5 minutes.
 Steel hard at cone 010.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Colo%.
 Per Cent. Per Cent. Per Cent.
 950'C. 3.2 6.46 17.20 Salmon.
 1050 4.2 6.02 16.30 Salmon.
 1150 6.7 6.61 16.60 Gray.
 1190 7.0 5.49 13.40 Gray.


 A brownish-gray, slightly sandy clay occurs in the Annuttalaga Hammock about one-half mile north of Brooksville and extends northward for about two miles. The thickness of the deposits is not known, but is as much as eight feet in places. The clay is suitable for a soft, porous common building brick of only fair quality. Its physical properties are: