Orpiment, yellow, description and uses of, 214 ——, red, 214 Oxides, 11 Oxygen, 10 —— gas, 11 P. Paint, white, how to prevent pernicious effects of, 205 —— ——, made of oxide of zinc, 211 Paviour’s flags, of what made, 234 Paving stones, 225, 233 Pearl─ash, what it is, and how prepared, 136 —— white, of what made, and use of, 218 Pebbles, 46 Petrifactions. See Tufa. Petrifying springs, at Knaresborough and Matlock, 113 Petroleum, description, properties, and uses of, 157 Petunzè, 69 Pewter, of what made, 202 Phosphats, 12 Phosphoric acid, 12─20 Phosphorus, 19 Pinchbeck, of what made, and use of, 187 Pipe─clay, description and use of, 72 Plaster of Paris, of what made, and use of, 118 Plate glass, how made, 56 Plating of copper, &c. how performed, 180 Platina, description, properties, and uses of, 166, 167 Pompey’s pillar, of what formed, 230 Ponderous earth. See Barytes. Porcelain─clay, description and use of, 74 ——, Chinese, French, and English porcelain, account of, 74 ——, how manufactured, glazed, and painted, 74, 75 ——, biscuit, how made, 47, 75 Porphyry, description and uses of, 229 Portland stone, description and use of, 114 Potash, description of, how obtained, and use of, 135 Potstone, description and use of, 90 Pottery, how made, 73 Powder blue, of what made, and use of, 222 Prince’s metal, what it is, and for what used, 187 Printer’s types, of what made, 205, 218 Pumice, description and use of, 67 Pyrites, description, properties, and uses of, 198, 199 Q. Quartz, description, properties, and uses of, 44 ——, rock, 231 Queen’s ware pottery, of what made, 73 Quick lime, how made, 98 Quicksilver. See Mercury. R. Red chalk and Reddle, description and uses of, 199 Realgar, description and uses of, 214 Rocks, systematic arrangement of, 7, 224 ——, primitive, description of, 224 ——, secondary, 231 ——, transition, 232 ——, floetz or flat, 233 ——, volcanic, 235 Rock oil. See Naphtha. Roe stone. See Ketton stone. Roofing slate, description of, 76 —— ——, how to choose, 77 —— ——, Welsh and Westmoreland, 78 —— ——, French, 76 —— ——, various uses of, 77─80 Rolling stones, of what made, 234 Rotten stone, description and use of, 76 Rouge, of what made, 84, 91 Rubellite, valuable specimen of, 41 Ruby, Oriental, description of, 31 ——, whence imported, value, properties, and uses of, 31, 32 ——, spinel, description, value, and uses of, 32 ——, Balais, 32 ——, false, 49 Ruin marble. See Florence marble. S. Sal ammoniac, description of, how made, and uses of, 138, 139 Salt, common, description and uses of, 129 ——, mines in Poland, description of, 129 ——, mines in Chester, 130 ——, mountains of, in Spain, 130 —— springs, 131 Salt, how manufactured, 131 ——, bay, 132 ——, spirit of, how made, and uses of, 132 Saltpetre. See Nitre. Sand, common, description and uses of, 52 Sandstone, 234