A PRELIMINARY REPORT ON CLAYS OF FLORIDA 103

strength and tensile strength stand in direct relation to each other. The tensile strength is determined by molding the clay into briquettes similar to those employed in testing cement. These, after being properly dried, are pulled apart in a tensile strength machine. The cross section of the tensile strength in pounds per square inch is -omputed. The tensile strength test is now superceded by the transverse strength test.
 In determining the transverse strength, bars Of clay six inches long and one inch in cross-section are made. They are then thoroughly dried first at room temperature and finally at 110' C. After the width and thickness of the bars are measured they are placed on supports six inches apart and pressure is applied to the upper surface midway between the supports. The modulus of rupture is then computed in pounds per square inch by the following formula:
 3 w I
 Modulus of Rupture...........
 2 b h2
 Where w is the breaking load,
 I the distance between supports,
 b the breadth of the bars, and
 h the height of the bars.

 The bonding test is made in order to determine the bonding power of a clay. This is made by mixing equal parts of standard sand and clay and the mixture is molded into bars and broken as in the transverse strength test. The modulus of rupture is then calculated. The bonding power of a clay is its ability to carry quantities of non-plastic material. The modulus of rupture of the sand-clay mixture may be either higher or lower than that of the clay alone.
 The color of a fired clay is always of importance and hence is noted. This is particularly, eajw i 4 sin' e heolor of the raw clay is no indication of its fired (of.