322 



INDEX 



Tropic of Capricorn, 52, 191 



Troposphere, nature and composition of, 4 



Tuberculosis, 222 



Tucson water supply, 67 



Tungsten, in electric lamp filaments, 102 



Tungsten lamp, 102 



Tuning, principle of, 283 ; radio sets, 286 



Turbine, 162, 248; experiment, 163; steam, 



165; water, 166; and electric generator, 



251 

 Typhoid fever, in sewage, 73 ; vaccination 



for, 219; and house fly, 222 



Ultraviolet light, and vitamin D, 82; as 



ether waves, 106 

 Undershot water wheel, 166 

 Unwins, Lieutenant, 312 

 Uranus, as a planet, 183 

 Ursa major, 173 

 Ursa minor, 173 



Vaccination, 218 



Vacuum, 7, 10 



Vacuum cleaner, 10 



Vacuum tubes, how constructed, 252; in 



wireless, 279; principle of, 283; and 



radio receiving, 285 

 Vail, Alfred, 268 

 Valve, 7 



Van Drebble, 306 

 Vaporization, 29 

 Variation, in living things, 233 

 Vegetables, 84 

 Veins. 95 



Velocity of light, 104 

 Ventilation, 21, 22, 25 

 Venus, 181 

 Vernal equinox, 191 

 Vesuvius, 205 

 Vibration, 16, 129 

 Villi, 95 



Vitamins, 80, 82; foods rich in, 83 

 Vitreous humor, 113 



Voice, human, 19 



Voice wave, 282 



Volcanoes, 205 



Volt, 258, 260 



Volta, Alessandro, 242, 260 



Voltage, of transformer, 252 



Voltaic pile, 242 



Volt meter, 260 



Von Guericke, Otto, 5 



Vorticella, 229 



Waste trap, 73 



Water, removal of hardness from, 58, 61 ; 

 purified by filtration, 58 ; by chemicals, 

 58; by distillation, 58; composition of, 

 55, 59; electrolysis of, 58; impurities 

 found in, 59; requirements of for 

 drinking, 59 ; purification of in the 

 home, 60; soft, 61 ; purification by aera- 

 tion, 66; and sewage disposal, 73; ef- 

 fect of freezing of on rocks, 203 ; 

 chemical work of on earth's surface, 

 203; and soil, 209; and bacteria, 217 



Water cycle, 33, 35 



Water power, available and developed in 

 the world, 167; and electric power, 251 



Water supply, sources of, 62; from wells, 

 63; of New York City, 64; of St. 

 Louis, 65; of Tucson, 67; of Los An- 



geles, 67; relation of to health, 69; 



pressure in, 71, 72; distribution of, 72 

 Water table, 63 

 Water vapor, in the air, 23 

 Water wheels, 166 

 Watson, Thomas 273 

 Watt, defined, 258 

 Watt, James, 165, 261 

 Waves, experiment, 278; wireless, 279, 



280; radio frequency, 284; damped, 



284; modulated, 285 

 Wave length, of visible spectrum, 106; of 



wireless waves, 280 

 Wax, composition of, 100 

 Weather, importance of, 28 ; and evapora- 

 tion, 30-32; and condensation, 33-36; 



and winds, 37-41 ; and weather lore, 42 ; 



and its prediction, 42-47 ; and climate, 

 51-55 



Weather Bureau, organization and opera- 

 tion of, 46 



Weathering, agents of mechanical, 202; of 

 chemical, 203 



Weather instruments, 45, 46 



Weather maps, 43, 46 



Wedge, 161 



Weight, why substances have, 149 



Wells, 63; artesian, 64; oil, 124 



Welsbach, 101 



Westerlies, prevailing, 40 



Westinghouse, Geo., 14 



Wet bulb thermometer, 29 



Wheatstone, 239 



Wheel and axle, 159 



White corpuscle, 95 



Windlass, 159 



Winds, cause of, 38, 39; about low and 

 high pressure areas, 38 ; diagram of 

 causes of, 40; of the world, 41; trade, 

 41 ; monsoons, 41 ; in weather forecast- 

 ing, 45 ; and erosion, 204 



Wireless, experiment, 277, 278 : waves set 

 up, 279; length of waves, 280 



Wiring for home, 255 



Wool, 142 



Work, 157 



Wrigglers, 224 



Wright brothers, 310 



Writing, history of, 265 



Xenon, 23 



Year, length of, 191 

 Yeast, 87, 89 

 Yellow fever, 223 



Zeppelin, Count Ferdinand, 309 

 Zones, of the world, 52 



