Perhaps the most general mistake made is in relating sounds and colors by stressing a mere analogy too far. Notwithstanding the vibratory nature of the propagation of sound and light, this is no reason for stressing a helpful analogy. After all it is the psychological effect that is of importance and it is absurd to attribute any connection between light-waves and sound-waves based upon a relation of physical quantities. No space will be given to such a relation because it is so absurdly superficial; however, the language of music will be borrowed with the understanding that no relation is assumed.

A few facts pertaining to vision will indicate the trend of developments necessary in the presentation of mobile light. The visual process synthesizes colors and at this point departs widely from the auditory process. The sensation of white may be due to the synthesis of all the spectral colors in the proportions in which they exist in noon sunlight or it may be due to the synthesis of proper proportions of yellow and blue, of red, green, and blue, of purple and green, and a vast array of other combinations. A mixture of red and green lights may produce an exact match for a pure yellow. Thus it is seen that the mixture of lights will cause some difficulty. For example, the components of a musical chord may be picked out one by one by the trained ear, but if two or more colored lights are mixed they are merged completely and the resultant color is generally quite different from any of the components. In music of light, the components of color-chords must be kept separated, for if they are intermingled like those of musical chords they are indistinguishable. Therefore, the elements of harmony in mobile light must be introduced by giving the components different spatial positions.

The visual process is more sluggish than the auditory process; that is, lights must succeed each other less rapidly than musical notes if they are to be distinguished separately. The ear can follow the most rapid execution of musical passages, but there is a tendency for colors to blend if they follow one another rapidly. This critical frequency or rate at which successive colors blend decreases with the brightness of the components. If red and green are alternated at a rate exceeding the critical frequency, a sensation of yellow will result; that is, neither component will be distinguishable and a steady yellow or a yellow of flickering brightness will be seen. The hues blend at a lower frequency than the brightness components of colors; hence there may be a blend of color which still flickers in brightness. Many weird results may be obtained by varying the rate of succession of colors. If this rate is so low that the colors do not tend to merge, they are much enriched by successive contrast. It is known that juxtaposed colors generally enrich one another and this phenomenon is known as simultaneous contrast. Successive contrast causes a similar effect of heightened color.

An effect analogous to dynamic contrast in music may be obtained with mobile light by varying the intensity of the light or possibly the area. Melody may be simply obtained by mere succession of lights. Tone-quality has an analogy in the variation of the purity of color. For example, a given spectral hue may be converted into a large family of tints by the addition of various amounts of white light. Rhythm is as easily applied to light as to music, to poetry, to pattern, or to the dance, but in mobile lights its limitations already have been suggested. However, it is bound to play an important part in the art of mobile light because rhythmic experiences are much more agreeable than those which are non-rhythmic. Rhythm abounds everywhere and nothing so stirs mankind from the lowliest savage to the highly cultivated being as rhythmic sequences.

Many psychological effects of light have been recorded from experiment and observation and affective values of light have been established in various other byways. It is possible that the degree of pleasure experienced by most persons on viewing a color-harmony or the delightful color-melody of a sunlit opal may be less than that experienced on listening to the rendition of music. However, if this were true it would offer no discouragement, because absolute values play a small part in life. Two events when directly compared apparently may differ enormously in their ability to arouse emotions, but the human organism is so adaptive that each in its proper environment may powerfully affect the emotions. For example, those who have sported in aerial antics in the heights of cloudland or have stormed the enemy's trench are still capable of enjoying a sunset or the call of a bird to its mate at dusk. The wonderful adaptability of the inner being is the salvation of art as well as of life.

In the rendition of mobile light it is fair to give the medium every advantage. Sometimes this means to eliminate competitors and sometimes it means to remove handicaps. On the stage light has had competitors which are better understood. For example, in the drama words and action are easily understood, and regardless of the effectiveness of light it would not receive much credit for the emotive value of the production. In the wonderful harmony of music, dance, and light in certain recent exhibitions, the dance and music overpowered the effects of lights because they speak familiar languages.



A number of attempts have been made to utilize light as an accompaniment of music and some of them on a small scale have been sincere and creditable, but a much-heralded exhibition on a large scale a few years ago was not the product of deep thought and sincere effort. For example, colored lights thrown upon a screen having an area of perhaps twenty square feet were expected to compete with a symphony orchestra in Carnegie Hall. The music reached the most distant auditor in sufficient volume, but the lighting effect dwindled to insignificance. Without entering into certain details which condemned the exhibition in advance, the method of rendition of the light-accompaniment revealed a lack of appreciation of the problems involved on the part of those responsible.

Incidentally, it has been shown that the composer of this particular musical selection with its light accompaniment was psychologically abnormal; that is, he was affected with colored audition. It is not yet established to what extent normal persons are similarly affected by light and color. Certainly there is no similarity among the abnormal and none between the abnormal and normal.

If light is to be used as an accompaniment to music, it must be given an opportunity to supply "atmosphere." This it cannot do if confined to an insignificant spot; it must be given extensity. Furthermore, by the use of diaphanous hangings, form will be minimized and the evanescent effects surely can be charming. But finally the lighting effects must fill the field of vision just as the music "fills the field of audition" in order to be effective. There are fundamental objections to the use of mobile light as an accompaniment to music and therefore the future of the art of mobile light must not be allowed to rest upon its success with music. If it progresses through its relation with music, so much is gained; if not, the relation may be broken for music is quite capable of standing alone.

There is a tendency on the part of some revolutionary stage artists to give to lighting an emotional part in the play, or, in other words, to utilize lighting in obtaining the proper mood for the action of the play. Color and purely pictorial effect are the dominant notes of some of them. All of these modern stage-artists are abandoning the intricately realistic setting, and, as a consequence, light is enjoying a greater opportunity. In the more common and shallow theatrical production, lighting and color effects have many times saved the day, and, although these effects are not of the deeper emotional type, they may add a spectacular beauty which brings applause where the singing is mediocre and the comedy isn't comedy. The potentiality of lighting effects for the stage has been barely drawn upon, but as the expressiveness of light is more and more utilized on the stage, the art of mobile light will be advanced just so much more. Light, color, and darkness have many emotional suggestions which are easily understood and utilized, but the blending of mobile light with the action is difficult because its language is only faintly understood.

It is futile to attempt to describe a future composition of mobile light. Certainly there is an extensive variety of possibilities. A sunset may be compressed into minutes or an opalescent sky may be a motif. Varying intensities of a single hue or of allied hues may serve as a gentle melody. Realistic effects may be introduced. The expressiveness of individual colors may be taken as a basis for constructing the various motifs. These may be woven into melody in which rhythm both in time and in intensity may be introduced. Action may be easily suggested and the number of different colors, in a broad sense, which are visible is comparable to the audible tones. Shading is as easily accomplished as in music and the development of this art need not be inhibited by a lack of mechanical devices and light-sources. The tools will be forthcoming if the conscientious artist requests them.

Whatever the future of the art of mobile light may be, it is certain that the utilization of the expressiveness of light has barely begun. It may be that light-music must pass through the "ragtime" stage of fireworks and musical-revue color-effects. If so, it is gratifying to know that it is on its way. Certainly it has already served on a higher level in some of the artistic lighting effects in which mobility has featured to some extent.

If the art does not develop rapidly it will be merely following the course of other arts. A vast amount of experimenting will be necessary and artists and public alike must learn. But if it ever does develop to the level of a fine art its only rival will be music, because the latter is the only other abstract art. Material civilization has progressed far and artificial light has been a powerful influence. May it not be true that artificial light will be responsible for the development of spiritual civilization to its highest level? If mobile light becomes a fine art, it will be man's most abstract achievement in art and it may be incomparably finer and more ethereal than music. If this is realized, artificial light in every sense may well deserve to be known as the torch of civilization.



READING REFERENCES

No attempt will be made to give a pretentious bibliography of the literature pertaining to the various aspects of artificial lighting, for there are many articles widely scattered through many journals. The Transactions of the Illuminating Engineering Society afford the most fruitful source of further information; the Illuminating Engineer (London), contains much of interest; and Zeitschrift fuer Beleuchtungswesen deals with lighting in Germany. H. R. D'Allemagne has compiled an elaborate "Historie du Luminaire" which is profusely illustrated, and L. von Benesch in his "Beleuchtungswesen" has presented many elaborate charts. In both these volumes lighting devices and fixtures from the early primitive ones to those of the nineteenth century are illustrated. A few of the latest books on lighting, in the English language, are "The Art of Illumination," by Bell; "Modern Illuminants and Illuminating Engineering," by Gaster and Dow; "Radiation, Light and Illumination," by Steinmetz; "The Lighting Art," by Luckiesh; "Illuminating Engineering Practice," consisting of a course of lectures presented by various experts under the joint auspices of the University of Pennsylvania and the Illuminating Engineering Society; "Lectures on Illuminating Engineering," comprising a series of lectures presented under the joint auspices of Johns Hopkins University and the Illuminating Engineering Society; and "The Range of Electric Searchlight Projectors," by Rey; "The Electric Arc," by Mrs. Ayrton; "Electric Arc Lamps," by Zeidler and Lustgarten, and "The Electric Arc," by Child treat the scientific and technical aspects of the arc. G. B. Barham has furnished a book on "The Development of the Incandescent Electric Lamp." "Color and Its Applications," and "Light and Shade and Their Applications," are two books by Luckiesh which deal with lighting from unique points of view. "The Language of Color," by Luckiesh, aims to present what is definitely known regarding the expressiveness and impressiveness of color. W. P. Gerhard has supplied a volume on "The American Practice of Gaspiping and Gas Lighting in Buildings," and Leeds and Butterfield one on "Acetylene." A recent book in French by V. Trudelle treats "Lumiere Electrique et ses differentes Applications au Theatre." Many books treat of photometry, power-plants, etc., but these are omitted because they deal with phases of light which have not been discussed in the present volume. "Light Energy," by Cleaves, is a large volume devoted to light-therapy, germicidal action of radiant energy, etc. References to individual articles will often be found in the various indexes of publications.

THE END



INDEX

Aaron, 43

Accidents: 8; street-lighting in relation to, 225 et seq.; percentage (table) of, due to improper lighting, 231

Acetylene: 62; light-yield of, 106, 107, 170, 187, 191

Actinic rays: effect of, upon human organism, 275

Africa, public lighting in ancient, 31

Agni, god of fire, 40

Air-pump, 130

Air-raids, 225

Alaska, 18, 29

Alchemy, 20

Aleutians, 18

Alexandria, 43, 163

Allylene, 106

Aluminum, 108, 179, 180

Amiens, Treaty of, 69

Amylene, 106

Aniline dyes, 106

Animal: distinction between, and human being, 3; 15; production of light, 24 et seq.; sources of light, 30, 31; oils, 51

Antimony, 294

Antioch, 153

Arago, 114, 196

Archbishop of Canterbury, 49

Archimedes, 19

Arc: lamps, 69, 89; electric, 111 et seq.; distinction between spark and, 112; Davy's notes on electric, 113; formation of, 115, 116; Staite and enclosed, 117, 118; principle of enclosed, 118, 119; types of, 120; flame-, 121, 122; luminous, 122; electric, 127; luminous efficiency of electric (table), 124; 160 et seq.; -lamp in lighthouses, 168 et seq.; magnetite-, 187; 261

Ardois system of signaling, 199

Argand, Ami: 52; inaugurates new era in artificial lighting, 53, 54; 63, 70, 76, 77, 78, 97, 167, 196

Argon, 137

Aristophanes, "The Clouds," 19

Art Museums, 9, 13, 322, 323

Asbestos, 170

Asia: public lighting in ancient, 31, 39

Automobiles, 238

Babylon, 39

Bacteria: effect of artificial light upon, 272 et seq.; 281, 282

Bailey, Prof. L. H., 250

Baltimore, 98

Bamboo: carbon filaments, 169

Bartholdi, 302, 303

Beacons. See Lighthouses.

Beck, 186

Beecher, 72

Beeswax, 35, 51

Benzene, 106

Bible, cited on importance of artificial light, 42-44

"Bluebird, The," Maeterlinck, 9

Blue-prints, 261

Bollman, 98

Bolton, von, 132, 133

Bombs, illuminating, 182 et seq.

Boston Light, 164, 165, 166, 177

Bowditch, production of regenerative lamp by, 78, 79

Boy Scouts, 17

Bremer, 120

Bristol University, 252

Brush, 68, 159

Building, 8

Bunsen, 81, 85, 89, 148, 149

Bureau of Mines: cited on open flames, 234; 236

Burning-glasses, 19, 20. See also Lenses.

Butylene, 106

Byzantium, 34

Caesar, 163

Canada, 254

Candle-hour, defined, 215

Candles: progress and, 7; 25, 28, 29, 30, 33; religious uses of, 34, 35; as a modern light-source, 36, 37; ceremonial uses of, 38 et seq.; 44, 48, 57, 82, 97, 222, 299, 304

Calcium, 107, 108

Carbolic acid, 106

Carbon: 53, 80, 81; physical characteristics of, 80, 81; 90, 104, 105, 128, 129, 144, 170

Carbon filament: 127 et seq.; preparation of, 129, 130, 131; luminous efficiency of, 131, 132; lamps, 161; lamps in greenhouses, 250 et seq.

Carbons, formation of, 115, 116

Carbureted hydrogen, 75

Carcel, invention of clockwork lamp by, 54, 55

Cat-gut, 130

Ceria, 85, 101

Charleston, S. C., 185

Charcoal: 113; uses of, for electrodes, 115

Chartered Gas Light and Coke Co., London, 74

Chemistry: artificial light and, 256-268

Chicago, 62, 304, 305

Chimneys, 54, 60, 62

China, 19, 31, 32

Chlorate of potash, 22

Christ, 33, 46, 47

Christians, "children of light," 42

Christmas trees, 43, 304

Chromium, 294

Church of England, 49

Cities: economy of artificial lighting in congested, 13

Civilization: effect of artificial light upon, 4 et seq.; fire and, 15

Clark, Parker and, 139

Clayton, Dr.: invention of portable gas-light by, 64; quoted, 64, 65; experiments of, with coal-gas, 67

Claude, 147

Cleaves, Dr., quoted, 276, 277

Clegg, Samuel: 74; gas-lighting accomplishments of, 75, 76

Cleveland, 159

"Clouds, The," Aristophanes, 19

Coal: 32; as a light-source, 55; supply, 223; 228

Coal-gas: 63 et seq.; public lighting by, developed, 70 et seq.; analytical production of, 103, 104; yield of, retort (table), 105; analysis of, 106

Coal-mines, 234 et seq.

Cobalt, 294

Coke, 68, 105

Cologne, 157, 158

Colomb, Philip, 197

Color: 9; relation of artificial light to, 284 et seq.

Colza, 31, 52, 167

Combustion, 82 et seq.

Commerce, 8, 97

Constantine, 42

Copper, 262, 295

Cornwall, 63

Cotton: 101; carbon filaments, 129, 130

Cromartie, 78

Crookes, 90, 146

Crosley, Samuel, improvement of gas-meter by, 76

Crusies, 32

Daguerre, 258

Dancing, 346

Davy, Sir Humphrey: 33, 68, 73; first use by, of charcoal for sparking points, 112; notes of, on electric arc, 113; 114

Daylight, artificial, 12: 284 et seq.; application of, 287

Daylighting, 12-14

Dollond, 195

Doty, 61, 167

Drake, Col. E. L., discovery of oil in Pennsylvania by, 56

Drummond, Thomas: 171, 185, 196; quoted on signaling, 197

Dudgeon, Miss, 251, 252

Dyes, 256, 265

East Indies, 29

Eddystone Light, 166, 167

Edison: and problem of electric incandescent filament lamps, 128 et seq.; 129; quoted on birth of incandescent lamp, 130

Edward I, 274

Edward VI, 49

Efficiency, effect of artificial light upon, 14

Eggs: relation of artificial light to production of, 247, 248

Egypt: 31; sacredness of light in ancient, 39; 153, 195

Electric filament: 81, 127 et seq.: approximate value of, lamps (table), 138

Electric pile: construction of, 111; 127

Electricity: 13, 22; as a light-source, 57; for home-lighting, 62, 84; 87, 89; ignition of gas by, 102; lighting by, 109 et seq.

Electromagnetic waves, 68, 86, 87

Electromagnets, 114, 116

Electrodes, 113, 114, 115 et seq.; life of, 122

Elizabeth, Queen, 274

England: 32; petroleum discovered in, 56; gas-lighting in, 63 et seq.; 166, 251, 274

Erbia, 85

Esquimaux: 18; use of artificial light by, 31

Ethylene, 106

Factories: 13; artificial light in, 239 et seq.

Faraday, 113

Filaments, carbon, 129 et seq.

Finsen: 273, 274, 275; on stimulating action of artificial light, 277; 279, 280

Fire: importance of, to man, 5 et seq.; man's dependence upon, 15; mythical origin of, 16; making, 17 et seq.; production of, in the stone age, 18; in early civilization, 19; ancient worship of, 29, 299

Fireflies: 24, 81, 96, 148, 149, 150

"First Men in the Moon, The," H. G. Wells, cited, 148

Fish: artificial light as bait for, 249

Flame-arcs, 120, 121, 122, 187

Flames: 86, 88, 89; open, 233, 234 et seq.

Flint, 33

Fool's gold, 18

Fort Wagner, 185

France: lamps in, 55; early gas-light in, 72

Franchot, invention of moderator lamps by, 55

Frankland, 77

Franklin, Benjamin: 165; quoted, 210-212; 213

Fresnel, 167, 196

Friction, 16, 17

Gas: 13, 22; discovery of coal, 32, 33; early uses of, as light-source, 63 et seq.; installment of, pipes in England, 63, 64; Shirley's report on Natural, 66, 67; first public display of, lighting, 69; cost of, lighting, 71; first attempt at industrial, lighting, 72; first English, company, 74; first, explosion, 75; house, lighting, 76, 77; 80, 82; spectrum of, 90; modern, lighting industry, 97 et seq.; origin of lighting by, 98; first, works in America, 98; growth of, consumption in United States, 99; electrical ignition applied to, lighting, 102; pressure, 102, 103; water, 105; carbons in, 106; production of Pintsch, 109, 110; salts applied to, flames, 120; 157; Census Bureau figures on cost of, plants, 221, 222; 224, 341

Gas-burners: 63, 64, 77; candle-power of pioneer (table), 79; improvements in, 84

Gas-mantle: 61, 81; influence of, 99; characteristics of, 100 et seq.; 187

Gas-meter, Clegg's, 76

Gasolene: lamps, 55; 57

Gassiot, 114

Gauss, 196

Geissler, 146

General Electric Company, 132, 135, 136

Germany: development of lamps in, 56; early gas-lighting in, 72

Glass, 195, 290 et seq.

Glowers, 139

Glow-worms, 24

Glycerides, 52

Gold, 293

Gout, 275

Gramme dynamo, 117

Grass: 18; carbon filaments, 129

Greece: 39; sacred lamps in ancient, 41; 42

Greenhouses, carbon-filament lamps in, 250 et seq.

Hall of Fame, 134

Happiness, effect of artificial light upon, 14 Hayden and Steinmetz, 253

Health, artificial light in relation to, 269-283

Helium, 89

Hemig, 155

Hemp, 21

Henry, William, 75

Herodotus, 56

Hertz, 68

Hertzian waves, 271

Hewitt, Cooper, produces mercury-arcs, 124, 125

Home: artificial light in relation to, 6; lighting, 325 et seq.

Hindu: light in, ceremonials, 40

Hudson-Fulton Celebration, 306

Huygens, 195

Hydrocarbons, 82

Hydrogen, 81

Illiteracy, artificial light and, 9

Invention, 7, 97

Iowa, 238

Iridium, 129

Iron, 18, 262, 294

Iron pyrites, 18

Italy, 249

Jablochkov: electric candle of, 117

Jamaica, 19

Jandus, 118, 122

Japan: 19; use of oil in, 30; 281

Jerusalem, 43

Jews: artificial light among, 40

Journal, Paris, quoted, 210-212

Kerosene: 57; weight of, lumens, 60; 62, 187, 233

Kitson, platinum-gauze mantle applied by, 61

Laboratories: achievements of, 137

Lamps: 16, 25; Roman, 30; 31; invention of safety, 33; ancient funereal, 39; sacred, of antiquity, 41; ceremonial, 44; scientific development of oil, 51 et seq.; Holliday, 55; Carcel, 54, 55; Franchot's moderator, 55; gasolene, 55; development of, in Germany, 56; air pressure, 61; supremacy of oil, ends, 62; Bowditch's, 77, 78; 80, 97; mercury-arc, 126; electric incandescent filament, 127 et seq.; gem, 132; tungsten, 133 et seq.; luminous efficiency (table) of incandescent filament, 141; 299; in home, 328-333

Lange, 167

Lard-oil, 51

Lavoisier, 195

Lead, 262, 294

Le Bon, 72

"Legend of Montrose, The," Scott, cited on primitive lighting, 27

Leigh, Edmund, quoted, 226

Lenses, 20, 171 et seq.

Libanius, quoted, 153, 154

Liberty, Statue of, 301, 302, 303

Libraries, 9

Light: relation of artificial, to progress, 3 et seq.; as a civilizing agency, 3-14; primitive man and artificial, 4; Milton, quoted on importance of, 5; artificial, and science, 7; artificial, and industrial development, 8; Maeterlinck's tribute to, 9; Lincoln's debt to artificial, 9; symbolism of, 9, 10; therapy, 10; in war, 11; adaptations of, 12; 13; mythical origin of artificial, 16; earliest source of, 16; production of, in stone age, 18; matches as source of, 21; animals as, sources, 24, 25; primitive sources of, 24-37; evolution of artificial, sources, 24-37; development, 28 et seq.; early outdoor use of artificial, 28; Roman uses of artificial, 30; beginning of scientific, 33, 34; candles as modern, source, 36, 37; symbolism and religious uses of, 38 et seq.; Bible cited on artificial, 42-44; in relation to worship, 43, 45, 46; Argand's contribution to, 53, 54; coal as, source, 55; early uses of gas as, source, 63 et seq.; as a public utility, 70; first installation of industrial gas, 72; science of, production, 80 et seq.; causes of, radiation, 80, 81; 83; lime, 84; electric, 89 et seq.; principle of, production, 90, 91; sources, 93; various gas-burners', supply, 95; relative efficiency of, sources, 95, 96; in the home, 97; influence of, upon science, invention, and commerce, 97 et seq.; yield of acetylene, 106, 107; electric, 109; influence of gas upon development of artificial, 110; development of artificial, 111 et seq.; efforts to improve color of mercury-arc, 125; electric-incandescent-filament, 127 et seq.; effect of tungsten, upon, 133 et seq.; of the future, 143-152; in warfare, 178-193; signaling, 194-207; cost of, 208-224; and safety, 225 et seq.; improper use of, 229, 230; comparison of daylight and artificial, 240; reducing action of, 258; bactericidal action of, 272 et seq.; modifying, 284 et seq.; spectacular uses of, 298-309; expressiveness of, 310-324; utility of modern, 325-340; evolution of the art of applying, 341-356; mobile, 347, 348, 349, 350; psychological effect of, 351 et seq.; as an accompaniment to music, 352-354

Light-buoys, 10, 169

Lighthouses: 10, 163-177; optical apparatus of, 172 et seq.

Light-ships, 10, 169

Lighting-systems: comparison of, 12-14

Lime, 84, 107, 108, 294

Lincoln, Abraham, 9

Linen, 18

Link-buoys, 28

Lithopone, 265, 266

Liverpool, 167

Living: comparison of, standards, 238 et seq.

London, 152, 154, 155, 156, 157, 202

London Gas Light and Coke Company, 74

Lucigen, 61

Lumen-hour: defined, 215

Lumens: 60, 94, 215

Lutheran Church, 49

Lyceum Theatre, London, 73

Maeterlinck, Maurice, 9

Magazines, 8

Magdsick, H. H., 303

Magnesia: 84; Nernst's application of, 138

Magnesium, 179, 180

Magnetite arc, 187

Man: distinction between, and animal, 3; artificial light and early, 4; light-sources of primitive, 25

Manganese, 262, 268, 294

Mangin, 188

Mann, 129

Mantles, 95

Manufacturing, 8

Marconi, 68

Marks, 118

Matches: as light-sources, 21; 22, 82

Maxwell, 68

Mazda lamps, 289, 339

Mecca, 40

Mediterranean Sea, 163

Mercury-arc: Way's, 124; 125, 126; quartz, 125, 126; attempts to improve color of, light, 125

Middle Ages, 46, 47, 474

Milton, quoted, 5

Mirror, 19

Mohammedans, 40

Moore, Dr. McFarlan, 146, 147

Morality, effect of light upon, 9

Morse code: application of, to light-signaling, 198, 199

Moses, 195

Moving-pictures, 9, 260, 261

Munich, 72

Murdock, William: installment of gas-pipes by, 63; 68, 69, 70; quoted on industrial use of artificial, 71; 72, 73, 74, 76, 78, 217, 309

Museums: 13; utilization of artificial light by, 322, 323

Music: light as an accompaniment to, 352-354

Mythology, 16

Nantes, 85

Napoleon, 111

Napthalene, 106

National Heat and Light Co., 72, 74

Natural gas, 99

Navesink Light, 206

Nernst, 138, 139

Newspapers, 8

Newton, Sir Isaac: 7; quoted on discovery of visible spectrum, 87; 88

New York, 98, 165, 166, 206, 302, 304

Niagara Falls, 108, 306

Nickel, 262

Nielson, 77

Niepce, 258

Niter, 21

Nitrogen, 137

Norfolk, 169

Obesity, 275

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

Pigments, 265

Pintsch: production of, gas, 109, 110, 170

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

Staite, 117, 118

Stearine, 35, 52

Stearn, 129

Steel, 18, 33

Steinmetz, Hayden and, 253

Sterilization: quartz-mercury-arc and, 280, 281, 282

Stevenson, Robert Louis, quoted, 177

Stores, 13

St. Paul, 43

St. Paul's Cathedral, 300

Street-lighting: development of, 152-162

Sugar, 22

Sulphide of iron, 18

Sulphur, 18, 21, 179, 180, 294

Sulphuric acid, 21, 22

Sun, 8, 16, 19, 20

Swan, 129

Syracuse, 19

Syria, 153

Tallow, 34, 35, 51, 52

Tantalum: 132; filament lamps, 133

Tar, 68, 106

Telegraphy, 195

Telephony, 194

Textiles, 256

Thames, 169

Theaters, 9, 319 et seq.

Thoria, 85

Tin, 262

Tinder-boxes, 18, 19, 22

Travelers Insurance Company, 227

Trees, 26

Troy, 42

Tuberculosis, 273

Tungsten lamp, 161 et seq., 187, 261, 290, 303

Typhus, 273

Ultra-violet rays: 126, 150; in photographic electricity, 267, 268; 270, 272, 294

United States: petroleum in, 57; gas-consumption in, 99; 164, 165, 166

United States Geological Survey, cited on sale of gas, 222

United States Military Intelligence, 225, 226

Vacuum tubes, 81, 286

Venetians, 195

Ventilation, 13

Verne, Jules, 143

Vestal Virgins, 42

Volcanoes, 166

Volta, 111, 112, 127

Voltaic pile: construction of, 111, 127

Von Bolton. See Bolton.

War: and artificial light, 11, 178-193

Washington, 305

Water: sterilization of, by artificial light, 280 et seq.

Watson, Dr. Richard, 67, 68

Watt, 94

Waves: electro-magnetic, 68, 86, 125 et seq.

Wax, 34, 46, 51

Way: mercury-arc produced by, 124

Wells, 61

Wells, H. G., cited, 148

Welsbach, Auer von: 61; invention of mantle by, 99, 100, 133

Wenham, 78

West Indies, 25

Whale-oil, 31

Wicks, 35, 36, 53, 54, 58, 59

Winsor, 72, 73. See also Winzler.

Winzler. See Winsor.

Wolfram. See Tungsten.

Wood, 26, 27, 28

Woolworth Building, 302, 303

Wounds: treatment of, by artificial light, 10

X-ray: production of, tubes during War, 131; 137, 150, 270, 280

Young, James: discovers petroleum, 56

Yttria, 85

Zeitung, Cologne: 157; extract from, on street-lighting, 158

Zinc, 125, 130, 267

Zirconia, 84, 85



Transcriber's List of Corrections

LOCATION ORIGINAL CORRECTED

Chapter II and similiar material and similar material

Chapter XIII as a constant level at a constant level

Chapter XIV the carbons to distintegrate the carbons to disintegrate

Chapter XV John Pechham John Peckham coated with an allow coated with an alloy with various billiant with various brilliant key in depressed key is depressed

Chapter XVI has nearly doubled have nearly doubled

Chapter XVII this own indifference their own indifference

Chapter XXIII Nature's lighting varied Nature's lighting varies

Chapter XXIV so-called cadelabra so-called candelabra possibilties possibilities

READING REFERENCES ...Applications an Theatre." ...Applications au Theatre."

INDEX Photo-micography Photo-micrography Siemans Siemens

THE END