A PRELIMINARY REPORT ON CLAYS OF FLORIDA 205


 The lower clay has the following physical properties:

 Physical Properties of the Allentown Lower Clay (Lab. No. o-81).
 Plasticity, judged by feel........... Excellent.
 W ater of plasticity................. 24.15%
 Pore w ater ....................... 0.65%
 Shrinkage water .................. 23.50%
 Linear air shrinkage............... 8.0 %
 Volume air shrinkage.............. 30.6 %
 Modulus of rupture, average........ 244.6 pounds per square inch.
 Slaking test ....................... 10 m inutes.
 Steel hard at cone 1.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 0.0 21.99 38.20 White.
 1050 2.0 36.20 White.
 1150 5.0 15.98 18.60 Brown.
 1190 7.0 10.28 15.50 Brown.
 1230 7.0 9.60 10.50 Gray.
 1310 7.0 2.25 6.15 Gray.
 1370 9.5 2.00 5.95 Gray.
 1430 8.0 1.52 4.75 Gray.

 A sample of clay taken from Blackwater Creek, two and one-half
miles northeast of Milton, was tested by the Bureau of Standards in 1914.1
 Its physical properties indicate that it may be used for a good grade of common structural materials, but not for a vitrified product. It has
the following physical properties:

Physical Properties of Blackwater Creek Clay (Bureau of Standards, Sample No. 3).
 Plasticity.......................... Excellent.
 W ater of plasticity................. 28.9%
 Linear air shrinkage............... 6.0%
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent.
 850*C. 0.64 35.30 Salmon.
 950 35.80
 980 36.20
 1010 0.21 34.86
 1040 33.60 Buff.
 1070 32.15
 1100 31.10
 1130 1.44 29.55
 1160 29.05
 1190 28.80
 1220 28.05
 1250 1.17 27.30

 lSellards, E. H., Report on Tests for Paving Brick, Florida Geol. Survey Press Bulletin No. 7, 1915.