Part 42

Offices, 13

Oil: as a light-source, 29 et seq.; development of, lamps, 51 et seq.; 155; in lighthouse, 165 et seq.; 222, 224, 299

O'Leary, Mrs., and her lamp, 62

Olive-oil, 51, 52, 167

Orkney Islands, 29, 177

Osmium, 133

Oxygen: relative consumption of, by oil-lamps, 58, 59; 262

Ozone, 262

Painting, 342, 343, 347, 348, 349

Pall Mall, 74

Panama-Pacific Exposition: 304; artificial lighting of, 306, 307, 308, 309

Paper: 18; carbon filaments, 129, 130

Paraffin, 35, 57

Parker and Clark, 139

Paris: experimental gas-lighting in, 83, 84; Volta in, 111; 154, 185, 210, 212, 213

Peckham, John, 195

Pennsylvania: discovery of oil in, 56

Periodic Law, 145

Petroleum: 35, 51, 55; discovery of, 56; constitution of crude, 57; 58, 214

Pharos, 163

Philadelphia, 98, 99, 157

Phillips and Lee, 70, 72

"Philosophical Transactions of the Royal Society of London," 33; quoted on industrial lighting, 63; Shirley's report on natural gas in, 66, 67; quoted, 87

Phoenicians, 34, 39

Phosphorus, 21

Photo-micrography, 12

Photography: 126; early experiments in, 258; development of, 259; 291, 292

Picric acid, 106