106 FLORIDA GEOLOGICAL SURVEY-15TH ANNUAL REPORT


 Slip-Clays-A slip-clay is one used as a natural glaze. It should be of fine, even texture, have a high percentage of fluxing impurities, and should melt to a greenish or brown glass at a low cone.
 Miscellaneous-Clays used when burned, not included in the above mentioned groups, are: Gumbo-clay, having a high shrinkage, dense character, and fine grain, is used extensively as railroad ballast. Saggerclay is used in making the saggers or boxes in which white ware and other high grades of pottery are burned to protect them from the flame and fuel gases. Their refractoriness must be above that of the product burned. Wad-clay is a low gTade of fire clay used for sealing the joints between saggers when they are set in the kilus. Portland cement clay is that used in the artificial mixture of silica, alumina and lime which composes Portland cement. Clay or shale usually supplies the silica and alumina and limestone or marl the lime. The adaptibility of a clay for Portland cement can only be determined from a chemical analysis.
 Many clays are used in the unburned condition as paper fillers, paint pigments, abrasives, etc.
 USES OF CLAY
 The uses of clay are many and varied and any attempt to list all of them would be hopeless. The following uses listed by Ries1 summarizes those of raw clay as well as those of the fire or burned clay:
 Domestic-Porcelain, white ware, stoneware, yellow ware, Rockingham ware for cooking and for table service, majolica stoves, polishing brick, bath brick, firekindlers.
 Structural-Brick, common, front, pressed, ornamental, hollow, glazed, adobe, terra-cotta, roofing tile, glazed and encaustic tile, drain tile, paving brick, chimney flues, chimney pots, door knobs, fireproofing, terra-cotta lumber, copings, fence posts.
 Refractories-Crucibles and other assaying apparatus, gas retorts, fire-brick, glass pots, blocks for tank furnaces, saggers, stove and furnace bricks, blocks for fire boxes, tuyeres, cupola molds, mold linings for steel castings.
 Engineering-Puddle, Portland cement, railroad ballast, water conduits, turbine wheels, electrical conduits, road metal.
 Hygienic-Urinals, closet bowls, sinks, washtubs, bathtubs, pitchers, sewer pipe, ventilating flues, foundation blocks, vitrified bricks.
 Decorative-Ornamental pottery, terra-cotta, majolica, garden stands, tombstones.
 Minor Uses-Food adulterant, paint fillers, paper filling, electric insulators, pumps, fulling cloth, scouring soap, packing for horses' feet, chemical apparatus, condensing worms, ink bottles, ultramarine manufacture, emery wheels, playing marbles, battery cups, pins, stilts, and spurs for potters''use, shuttle eyes and thread guides, smoking pipes, umbrella stands, pedestals, filter tubes, caster wheels, pump wheels, electric porcelain, food rules, plaster, alum.

 1Ries, H., Clays, Their Occurrence, Properties and Uses, p. 252, 1908.
 To this list of clay products should be added tui-pentine cups, which are very extensively used in Florida. R. M. H.