A PRELIMINARY REPORT ON CLAYS OP 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 computed. 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strength test is now superceded by the transverse strength test.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 1 
Modulus of Rupture 
2 b h 2 
Where w is the breaking load, 
1 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 bond¬ 
ing power of a clay i? 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 necessary since the color of the raw clay is no indica¬ 
tion of its fired color. 
