A PRELIMINARY REPORT ON CLAYS OF FLORIDA 199

 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 9500C. 0.5 13.11 36.50 Brick red.
 1050 1.0 13.12 36.20 Brick red.
 1150 2.0 13.23 34.16 Brick red.
 1190 2.6 11.08 31.70 Brick red.
 1230 2.1 11.79 28.70 Brick red.
 1310 3.0 12.34 30.70 Brick red.

 A similar clay exposed about one-half mile north of Springside, Sec. 29, T. 9 S., R. 26 E., may also be used for a good grade of structural materials. It has an overburden of about one foot, ranges from twelve to twenty feet in thickness and underlies an extensive area in this region. This clay adjoins the Georgia Southern and Florida Railroad at Springside. A sample taken one-half mile north of the station has the following physical properties:

 Physical Properties of Springside Clay (Lab. No. o-44).
 Plasticity, judged by feel........... Excellent.
 W ater of plasticity................. 25.10%
 Linear air shrinkage............... 11.1 %
 Volume air shrinkage.............. 28.57%
 Modulus of rupture, average........ 791.4 pounds per square inch.
 Slaking test ....................... 1 hour.
 Overfires at cone 12.

 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 0.1 12.60 29.70 Brick red.
 1050 0.9 13.70 31.00 Brick red.
 1150 0.6 12.31 29.40 Brick red.
 1190 1.4 11.45 29.75 Brick red.
 1230 1.4 10.44 25.75 Brick red.
 1310 1.4 8.69 17.50 Dark red.

 Numerous other good common-brick clays occur in the region between Crescent City and Lake George. A brick plant was formerly operated at Denver where a common brick was made. Some of these clays are very similar in properties to those west of Palatka, and others seem to be identical with the Shell Bluff clay, found on the opposite side of Crescent Lake in Flagler County. (See Shell Bluff Clay, page 158.)
 Sandy clays, which may be used for a fair grade of common brick, are also found on the east side of the St. Johns River, near Orange Mills and San Mateo.