A PRELIMINARY REPORT ON CLAYS OF FLORIDA 173

 The plant is small and has only one kiln which has a 110,000 capacity. All the work is done by boys ranging in age from eight to eighteen years.
 The clay has excellent plasticity. Its linear fire shrinkage increases from 3.1 per cent at cone 010 to 10.6 per cent at cone 5. Its porosity and absorption percentages are low at cone 1 and remain so until after cone 9 is passed. This clay should be used only for common structural materials as common and face brick, fireproofing, hollow-block ware, drain tile and similar products and should be burned at about cone 010. Its physical properties are:

 Physical Properties of Florida Industrial School Clay (Lab. No. o-28).
 Plasticity, judged by feel........... Excellent.
 W ater of plasticity................. 36.65%
 Pore water ........................ 0.46%
 Shrinkage water ................... 36.19%
 Linear air shrinkage................ 14.40%
 Volume air shrinkage............... 38.10%
 Modulus of rupture, average........ 421.2 pounds per square inch.
 Slaking test ....................... 5 minutes.
 Steel hard at cone 010.
 Overfires at cone 12.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 3.1 11.95 26.00 Brick red.
 1050 10.6 8.05 20.75 Brick red.
 1150 10.6 2.10 8.60 Brick red.
 1190 12.6 1.70 7.50 Brick red.
 1230 12.6 1.67 5.80 Brick red.
 1310 13.6 1.50 6.10 Brick red.

 JEFFERSON COUNTY
 Jefferson County lies in north Florida and extends from the northern boundary of the State to the Gulf of Mexico. It is underlain by the Alum Bluff formation in the northern part of the county and the Chattahoochee formation in the southern part. A heavy mantle of red, coarse, sandy clay covers most of the county.
 Several brick plants have formerly been operated in the county. Three of these, located near Monticello, have worked a sandy, jointed, surface clay. Another small plant worked a red surface clay on the Bishop Homestead, four miles south of Aucilla. Clays from each of these localities may be used for common brick. The Bishop clay is too far from transportation to be of commercial importance.