Sapphire, Oriental, description of, how cut and set, 30 ——, properties, value, and use of, 30, 31 ——, false, or water, 49 Sardonyx, 57 Scots pebbles, description and use of, 62 Scythe─stones, how made, 234 Sea froth. See Meerschaum. Sea water, description and properties of, 244 —— ——, cause of its bitterness, and saltiness, 244 —— ——, uses of, 245 Serpentine, description and uses of, 89, 90 Shell silver, how prepared, 181 Shot, how made, 205 Sienite, description and uses of, 230 Silex, 15 Siliceous earth, 15 Silicium, 15 Silver, description of, 177 —— mines of Potosi and Norway, account of, 177, 178 ——, found in Scotland, 178 ——, extracted from lead, 178 ——, how extracted from its ores, 178 ——, value and uses of, and how alloyed, 179 ——, marks or stamps on silver plate explained, 179 ——, nitrat of, uses of, 181 ——, fulminating, extraordinary properties of, 182 ——, experiments with preparations of, 182 ——, how to gild, 172 Silver plate, how cleaned, 179 ——, ductility of, 179 Silver wire, 179 Silvering of looking─glasses, process of, 176 —— of metals, how performed, 186 —— of paper and wood, 181 Slate. See Roofing slate, and Writing slate. Slate pencils, how made, 78 Slickenside, extraordinary properties of, 218 Smalt, of what formed, and uses, 221 ——, strewing, 221 Smaragdus, 38 Snowdon diamonds, what they are, 47 Soap, how made, 127 Soap, boiling, illustration of, 127 ——, white, yellow, and soft, of what made, 128 —— of glass, what it is, 223 Soapstone. See Steatite. Soda, description and uses of, 126 ——, carbonat of, 128 ——, muriat of, 129 ——, sulphat of, 133 Solder, of what made, 205 Soot, uses of, 156 Spanish chalk, 84 Spanish white, of what made, 100 Spelter. See Zinc. Stalactites, description and uses of, 112 Stalagmite, 112 Steatite, description and uses of, 83 Steel, how made, and uses of, 192, 193 ——, Damascus, what, 192 ——, cast, how made, 192 ——, how to preserve from rust, 192 Strontian, 17 Stucco, of what made, 118 Sulphur, 19; description of, and how manufactured, 143 ——, uses and properties of, 143, 144 ——, singular experiment with, 145 Sulphuric acid, how prepared, properties and uses of, 145 Sympathetic ink, how made and used, 222 T. Table slates, how made, 78 Talc, common, or Venetian, description and uses of, 91 ——, indurated. See French chalk. Tamarind─tree, petrified. See Woodstone. Tartar, emetic, how prepared, 217 Tea─cups, how to gild, 173 Tea─urns, how browned, 141 Thunderbolts. See Meteoric stones. Tiles, how made, 72 Tin, description of, 200 ——, alloys of, 202 ——, block, and tin plate, what, and uses of, 200, 201 ——, how extracted from the ore, 200 Tin mines, and steam works, account of, 200 Tin putty, how made, and uses of, 202 Tin foil, how made, and uses of, 203 Tin─glass. See Bismuth. Tincal. See Borax. Tinning of iron and copper, how performed, 201