In the manufacture of clay products, including brick, tiling, terra cotta and pottery, the state takes high rank: the total value of pottery, terra cotta and fire-clay products increased from $8,940,723 in 1900 to $11,717,103 in 1905; in 1905 the most valuable pottery product was sanitary ware, valued at $3,006,406; and in that year New Jersey furnished 18.2% of the total pottery product of the United States, and was surpassed in this industry only by Ohio.
- Foremost among the useful products of the Carboniferous rocks is the coal (q.v.) itself; but associated with the coal seams in Great Britain, North America and elsewhere, are very important beds of ironstone, fire-clay, terra-cotta clay, and occasionally oil shale and alum shale.
This may be effected by mixing the dry chloridewith one-fifth of its weight of pure quicklime or one-third of its weight of dry sodium carbonate, and fusing the mixture in a, fire-clay crucible at a bright red heat.
Brick, potter's and tile clays are obtained most largely along the west border of the Coastal Plain, and fire-clay from the coal region of West Maryland; in 1907 the value of clay products was $1,886,362.
The city of Trenton is one of the two great centres of the American pottery industry, and in 1905 it manufactured more than one-half of the state's output of pottery, terra cotta and fire-clay products.