Tubercle bacillus, destroyed by sunshine, 248 Twilight, and dust motes, 46, 47 Ultra-violet Rays, remedial powers of, 248 Underground habitations, plan for unique, 180-184 United States, where climatic conditions are best in the, 245; fourth nation to establish weather service, 297 United States Weather Bureau, experiments with small gas balloons, 21; observations with kites by, 21, 22; storm warnings by, 24; and voluntary observers, 66; method of taking readings by, 66-79; ends of justice served by records of, 79-83; and prevention of frost, 95-97; maps prepared by, 112-160; timely warnings by, 117; when warnings are displayed by, 122; warnings of cold waves by, 126, 127; definition of “cold wave” by, 127, 128; and tornado warnings, 146, 147; on forecasting, 151-153; rules for forecasting at Milwaukee, Wis., 153-155; extent of area under observation by, 155-158; comparison of crime and records of, 215; rainfall records by, 237, 241; record of floods by, 241; and fake prevention, of hail, 290; stations and observations of the, 291, 292; fourth national weather service established, 297; the result of efforts by American scientists, 298; vast area under daily observation by, 298; number of observations twice daily by, 298; first work of, regarded as experimental, 299; advance in efficiency of, 299; growing faith in work of, 299; its study of types of storms, 299, 300; competitive examinations held by, 300; warnings by, now accepted, 300; warnings of West Indian hurricanes by, 300; value of property saved through warnings of, 301; utility of warnings of, 301, 302; and warnings to mariners on Great Lakes, 302; inception of storms detected by, 302; expectations of future forecasting by, 303, 304; first tentative, established, 305 Uranium, nucleus of atom of, 32 Uranus, atmosphere of, 3; and heat from sun, 3 Valleys, influence of, on temperature, 203, 204 Vaporization, latent heat of, 58, 59 Vegetation, oxygen and, 36; carbon dioxide and, 36; and frost, 85-97 Velocity increased by altitude, wind’s, 109-111 Ventilation, detrimental effects of poor, 34; need of, in closed or low places, 36; in places of habitation, 37; and underground apartments, 182, 183 Vera Cruz, Mexico, climate of, 209 Verkhoyansk, Siberia, extremes of temperature at, 196, 197; Christmas Day in, 273 Vienna, Austria, Christmas Day in, 271 V-shaped Lows. _See_ LOWS Warm waves, cause and duration of, 136, 137 Washington Monument, pressure of air at top of, 79