A PRELIMINARY REPORT ON CLAYS OF FLORIDA 211

of three feet of sand and hardpan and five feet of blue, sandy, plastic clay which is underlain by marl. The clay has good working qualities and may be used for a good grade of common structural materials. Its physical properties are:

 Physical Properties of Deep Creek Clay, DeLeon Springs (Lab. No. o-74).
 Plasticity, judged by feel........... Excellent.
 W ater of plasticity................. 24.50%
 Pore water ....................... 1.50%
 Shrinkage water .................. 23.00%
 Linear air shrinkage............... 9.3 %
 Volume air shrinkage.............. 32.6 %
 Modulus of rupture, average........ 635.0 pounds per square inch.
 Slaking test ....................... 5 minutes.
 Steel hard at cone 010.
 Overfires at cone 9.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 9500C. 0.7 12.19 27.80 Brick red.
 1050 0.7 12.80 28.20 Brick red.
 1150 0.7 10.39 26.00 Brick red.
 1190 0.7 8.26 27.65 Brick red.
 1230 1.2 7.82 27.00 Brick red.

 WAKULLA COUNTY
 Wakulla County, in middle Florida, is bordered on the south by the Gulf of Mexico and on the west by the Ocklocknee River. While the county is underlain by the Chattahoochee, Alum Bluff and Choctawhatchee formations, a heavy surface mantle of loose sand conceals them over much of the county.
 No clays of importance are known in the county. A sample from the southwestern part of the county, submitted by S. B. Crowder to the State Geologist, was tested in 1920 by the Bureau of Standards.1 The result of the test was as follows:
 Plasticity.......................... Fair.
 W ater of plasticity................. 30.0%
 Linear air shrinkage............... 12.7%
 Overfires at cone 10.
 Fired color, dark brown.

 WALTON COUNTY
 Walton County is situated in west Florida, just west of the Choctawhatchee River, and extends from the Florida-Alabama boundary to

 ILetter from Director U. S. Bureau of Standards to State Geologist of Florida, August 16th, 1920.