Pitch, 106

Plant-growth:  artificial light and, 11, 249 et seq.

Platinum, 85, 128, 129, 262

Plumbago, 113, 130

Plymouth, 166

Poetry, 346

Police, 162

Potash, chlorate of, 22

Priestley, Professor, quoted, 252

Printing, 8

Progress:  influence of fire upon, 15 et seq.

Prometheus, 16, 41

Propylene, 106

Ptolemy II, 163

Quartz:  18, 19;
  mercury-arcs, 125;
  uses of, 126;
  in skin diseases, 278, 279

Radiators, energy, 88 et seq.

Radium, 150

Railway Signal Association, 205

Railways:  light-signaling applied to, 205

Ramie fiber, 101

Rane, 250, 251

Rare-earth oxides:  85;
  properties of, 88, 99

Recreation, 9

Redruth, 63

Reformation:  ceremonial uses of light during the, 48, 49

Rheumatism, 275

Robins, Benjamin, 201

Rome, 30, 32, 34, 39, 41, 42, 44

Roentgen, 270, 280.
  See also X-ray.

Royal Society of London:  33, 63, 66, 67, 70, 73;
  and first gas explosion, 75, 111, 112

Rumford, 167

Rushlights, 28, 33

Russia, 281

Ryan, W. D’A., 306

Safety:  artificial light in relation to, 14, 225 et seq.

Salts:  chemical, 88, 89;
  metallic, 120;
  silver, 257, 258

Sandy Hook Light, 165, 166

San Francisco, 304, 306-309

Savages, 3, 15, 17

Sawyer, 129

Scheele, K. W., 133;
  quoted, 257, 258

Schools, 9

Science:  light and, 6, 7; 97;
  systematized, 268

Scotland:  26, 31, 32, 48;
  oil industry in, 56

Scott, Sir Walter, cited, 27, 98

Sculpture:  artificial light in relation to, 184

Search-lights, 11, 169

Section of Plant Protection, 225, 226

Selenium, 267, 293

Semaphore, 199

Shells:  illuminating, 179 et seq.

Shirley, Thomas:  quoted on natural gas, 66, 67

Siemens, 78

Signaling, 194-207

Silicon:  filament, 140

Silk:  artificial, 101;
  carbon-filaments, 129

Simpson, R. E., 227, 231

Silver, 258, 293

Skin diseases:  treatment of, 278, 279, 280

Skylights, 13

Sleep, 8

Smallpox, 274, 275

Smeaton, 166

Soho, 69, 72

South Africa, 129

Sparks:  33, 125

Spectrum:  visible, 86;
  Newton quoted on, 87;
  of elements, 89;
  of gases, 90; 120, 121;
  mercury, 124-126

Sperm, 31, 51, 52, 167

Spermaceti, 35, 51

Splinter-holders, 27, 28

Stage:  and artificial light, 319 et seq.; 343