A PRELIMINARY REPORT ON CLAYS OV VLORIDA 91

 TEXTURE
 The size of grains composing clay varies from small pebbles to extremely minute particles. In fact, these finer particles are at times so small as to remain in suspension in water an indefinite period. The size of grains, or texture, has an important influence in clays on their plasticity, shrinkage, porosity, fusibility and strength.
 Several methods of determining the texture of clays are commonly followed, and these are very similar to the methods used in the mechanical analysis of soils.1
 SLAKING

 Some clays when immersed in water will crumble to a powder in a few minutes, while others will at first break up into small masses which subsequently crumble. This process is known as slaking, and the test is usually made by mixing the clay with equal parts of ground potter's flint. The time necessary for a clay to slake varies from a few minutes in soft porous ones to several days or even weeks in others.
 A clay which slakes easily can be tempered more readily, and in case of a clay which must be washed, one which slakes readily is more rapidly disintegrated in the process.

 SHRINKAGE
 All clays exhibit a reduction in size in drying and burning which is termed shrinkage. The first is the air-shrinkage and the latter is the fireshrinkage. Both fire- and air-shrinkage are commonly measured in two ways, by volume or by linear determinations. The volume (or cubic) shrinkage is obtained by determining the volume of the test piece when first molded and again after drying or burning. The linear shrinkage is measured directly on the ware and expressed in percentage terms of the original length.
 In clay containing no water the clay particles are all in contact with each other. There are spaces, however, left between the particles. When the clay is brought into contact with water, these interstitial spaces are filled without the clay changing form. The water necessary to fill these interstitial spaces is termed the pore water. If additional water is

 1U. S. Dept. of Agriculture, Bur. of Soils. Bull. 4, p. 9, 1896.
 U. S. Dept. of Agriculture, Bur. of Soils. Bull. 64, 1900.