None
Power bum 53 effect of radiation 57 Primary standard color 179 standards of light 177 Prismatic reflection and refraction 221, 224 Problems of illumination 260 Protection against ultra-violet light 55 Protective device of arc lamp 151 mechanism of the eye against radiation 50 Protoplasm, effect of radiation 57 Pulsations of arc voltage 159 Pupil contraction 262 Putrefactive bacilli, effect of light 60 Pyro-luminescence 96 Pyrometers, visual 90 Quality or color of light 269 Quartz as most transparent body 31 transparent for ultrarviolet light 13 Radiant heat 1 Radiation efficiency 86 as a form of enei^gy 1 measurement 166 measured as power 166 power 72 alio 8ee Light. Radiators, comparison 202, 209 of Ught 187 separate from flame 135 Radio-active substances 14 Radio-fluorescence 95 Radio-luminescence 95 Radio-phosphorescence 95 Radio-therapy 61 Radium rays, harmful effects of 58 Range of frequencies of radiation 17 Reading distances measuring light 174 Rectification by arcs 114 Rectifying range of arc voltage 116 Red fluorescence 67 light, chemical action of 64 therapeutic effect 62 lines of mercury arc spectrum 120 INDEX. 801 PAOS Red mercuiy arc 121 Reduction factor of incandescent lamp 182 Reflected light from wails and ceiling, calculation 250 Reflection affecting light distribution 212 of light by body 28 regular, and light distribution 215 and shadow with radiator 210 Reflectors, comparison 215 as secondary radiators 212 as virtual radiators 215 Refraction law 23 and light distribution 221 spectroscope 25 Refractive index 23 and dielectric constant 24 and permeability 24 Regenerative flame lamp 126 R^^ular reflection 28, 215 and refraction 224 Regulator of arc machine 164 Reversed spectrum 27 Ring carbon 82 Room illumination, calculation 247 by incandescent lamp 242 Rounded circular surface as radiator 103 Sand blasted globe, diffraction 221 Saprophytic bacilli, effect of light 60 Searchlight beam, intensity 234 Secondary radiator and reflector 212, 216 Selective radiation 87 Sensitivity curve of the eye 43, 47 Sensitivity of the eye 263 and frequency 40 to ultra-violet light 54 maximum, of the eye 46 Separate radiator of flame 135 Series arc lamp 157 system of arc lighting. 162 Shadow 202 blurring of, in illumination 268 of diffused light 280 in illuminating engineering 266 of ne^tive carbon 203 of negative terminal of arc 148 number of 268 proper intensity in illumination 266 802 INDEX. FAttB Shadow photometer 171 in street lighting, defective 273 theory of 269 Shell of arc flame 110 Short burning carbon arc 160 Short ultra-violet light, destructive effect 52 Spherical intensity 257 Signal lights, color 08 Silicides as refractory bodies 78 Single loop filament, distribution curve 199 Smokiness of flame 130 Smoky flame 129 Soimd as longitudinal vibration 8 waves, frequency and wave length 17 Spark voltage 100 Specific effects of high frequency radiation 51 Spectrum of arc 118 and negative terminal 108 by diffraction 26 of flames 134 of luminescence 96 of radiation 17 by refraction 25 Sphere, illumination 287 as radiator 189 Spherical intensity 180 reduction factor of incandescent lamp 182 Stability curve of the arc 142, 144 limit of arc 143 Stable branch of arc characteristic 142 Standard candle 170 Starting of arc 106 by auxiliary arc 112 device of arc lamp 151 Steadying device of arc lamp 151 reactance or resistance of arc lamp 151 Stephan's law 70, 75 Stimulating effect of radiation 57, 59 Straight line as radiator 195 Street illmination by arcs 234 comparison of arc lamps 240 Street Ughting 226,272 calculation 238 comparison of illuminants 236 defects 273 Striated Geissler discharge 101 Subjective or apparent color 34 INDEX. 808 FAGS Subjective color, control in illumination 265 illumination 262 Sulphur flame 135 Sunburn 59 Sun spectrum 27 Surges, electrical, frequency and wave length 17 Symptoms of ultra-violet bums 54 Synthetic action of plants 65 Table illumination 253 Tanning 59 Tantalum lamp 80 Temperature of arc stream 108 of carbon filament 79 and frequency of radiation 73 of maximum efficiency of light production 74 measurement by radiation law 89 radiation 70 of flame 128 law of 84 standard 178 Therapeutic use of light 61 effects of radiation 57 Thermo-couple measuring radiation power 166 Thermo-luminescence 95 Threshold value of visibility 45 Titanides as refractory bodies 78 Titanium arc, white 123 carbide arcs 117, 123 Total illumination 226, 287 of room 253 Tower lighting 274 Transfer of arc between anodes 112 Transient electric phenomena 18 Translucent body 31 Transmission of light by body 28 Transparent 32 body 31 color 31, 32, 36 Transversal vibration 7 Tungsten lamp 80 as refractory element 78 Also see Wolfram. Typical arc 109 Ultra-red rays 12 frequency and wave length 14, 17 804 INDEX, PAOB Ultrarviolet arc lamp 12 bum 53 bum in wireless telegraphy 54 iron arc 119 lamp 135 light of arc 55 light and fluorescence 67 light haraif ul effect 62 therapeutic action 61 radiation, frequency 14 rays 12 frequency and wave length 17 Unidirectional conduction of electric arc 113 Unifom:! distribution illumination curve 229 or general illumination 269 illumination 226,260 in street lighting 235 Uniformity in street lighting 272 Uniforai and local illumination 264 total illumination 228 Unit of Ught 177 Unstable branch of arc characteristic 142 Unsteadiness of metal arcs 125 Vacuum arc 145 Vapor pressure of the arc 106 stream of the arc 105 tension of carbon 79 Vectgr quantities and light 284 Velocity of electrical radiation 4 light 2 in a medium 23 Vertical illiunination 227 Violet light, harmful eflFect ^ 52 specific effect 62 Violle standard of light 177 Virtual radiator 221 and reflector 216 Visible light, frequency and wave length 17 radiation 10 power measurement 168 range . ^ 14 and temperature 74 Visibility range of radiation 37 Visual pyrometers 90 Walls, albedo 246 Warm light 48 INDEX, 806 PAOS Waste of light flux by absorption 261 Water as traDsparent body 31 Wave length determination 6 of visible radiation 10 Welsbach mantle 92, 136 White 32 body 29 iron arc 119 Whiteness or albedo 30 Willemite fluorescence 13 Wireless telegraph waves, frequency and wave length 15, 17 ultrarviolet bum 64 Wolfram as refractory element 77 also see Tungsten. X-ray frequency and wave length 14, 17 harmful effects of 58 specific action 56 Zinc arc, constants 140 rectification 117 .. OP THE UNIVERSITY or YC 12910. 