184 fLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT


 Both of these clays are cream-burning and retain a soft, porous texture up to their fusion points. The top clay melts at cone 12 and the lower one at cone 9. Neither of them are desirable for the manufacture of high-grade clay products. A light, soft, porous structural material of low strength may be made from the lower clay, but very careful grinding and mixing would be necessary. Both of these clays are high iti soluble salts. The upper one contains 24.4 per cent lime and 6.613 per cent magnesia, as may be seen from the analysis given on the next page.
 Its physical properties are:

 Physical Properties of W. J. McLaughlin Top Clay (Lab. No. o-72).
 Plasticity, judged by feel........... Excellent.
 Water of plasticity................. 29.10%
 Pore water......................... 0.19%
 Shrinkage water ...................28.91%
 Linear air shrinkage............... 4.80%
 Volume air shrinkage.............. 12.10%
 Modulus of rupture, average........ 265.9 pounds per square inch.
 Slaking test ....................... 10 minutes.
 Overfires at cone 12.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950'C. 0.8 6.19 67.20 Cream.
 1050 1.2 5.87 66.80 Cream.
 1150 2.2 5.30 63.50 Cream.
 1190 5.2 3.87 54.50 Cream.
 1230 3.2 3.93 57.50 Cream.
 1310 2.2 4.05 60.10 Cream.

 The lower clay c6ntains 9.1 per cent lime and 5.54 per cent magnesia, as may be seen from the analysis given below. Its physical properties are:
 Physical Properties of W. J. McLaughlin Bottom Clay (Lab. No. o-19).
 Plasticity, judged by feel........... Excellent.
 Water of plasticity................. 38.40%
 Linear air shrinkage............... 12.70%
 Volume air shrinkage.............. 36.95%
 Modulus of rupture, average........ 544.9 pounds per square inch.
 Slaking test ....................... 3 days.
 Overfires at cone 9.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 0.2 26.45 48.75 Cream.
 1050 2.3 26.20 47.50 Cream.
 1150 4.8 25.80 43.30 Cream.
 1190 4.3 20.75 43.40 Cream.
 1230 6.3 16.75