Cyclone, general cause of, 98; general whirl of, 103; gyration of, 107-109; the disk of air constituting a, 119; an area of low pressure, 119; action of the air in and around the, 120; movement of the, 120; general extent of, 141; destructive force of, 142 Cyclones, localities in which, are formed, 156, 157 Dawson, Canada, annual range of temperature at, 169 Death rate, excessive humidity increases, 216, 217 Death Valley, Cal., intense heat in, 275-277; area and forbidding character of, 276; temperature records taken in, 276, 277 Deflection, due to earth’s rotation, 107 Density of earth’s atmosphere at different levels, 6 “Descriptive Meteorology,” 141; reasons for change of opinion on change of climate expressed in, 233 Desert of Sahara, Africa, intense heat in, 279 Dew point, 38; and frost, 89, 90 Diathermancy, 56, 124 Dirigible balloon, as competitor of railroad, 19; importance of developing the, 27 Disease, elevation diminishes bacteria of, 10; amelioration of, by sunshine, 248 Drainage, influence on frost, 94 Droughts, the breaking of, 136 Dunwoody, Brig. Gen. H. H. C., expert forecaster and chief of Weather Bureau, 306 Dust, in the atmosphere, 33 Dust motes, absence of, at higher altitudes, 9; interference of sun’s rays by, 10; source of, 43, 44; vary according to locality, 44; counting of, 44, 45; and diffusion of light, 45, 46; and twilight, 46, 47 Eads Bridge, St. Louis, freak of tornado and the, 147 Earth, early condition of, 1; death of, due to lack of heat from sun, 3, 4; early condition of atmosphere of, 5; transmission of sun’s rays to, 7, 8; water vapor in atmosphere of, 8; four atmospheres of the, 29-47; comparison of heat of sun and of, 48; circulation of winds and rotation of, 98-111; deflection of winds due to rotation of, 107-109; conditions if axis of, were vertical, 164; variations of heat of morning, midday, and evening, 166; change of seasons and the, 166; percentage of solar rays reaching the, 166-168; lag of temperatures of the, 168; kept from freezing by water vapor, 170; how the, cools at night, 171, 172; great heat of interior of the, 178, 179; a poor reflector, conductor, and radiator, 179; temperatures at various depths in the, 179; warmer than air next above, 180; conditions if, were all land, 188-190; if axis of, were perpendicular to plane of orbit, 188, 189; conditions if, were all water, 190-192; the real, of land, water, and inclined axis, 192 Eclipse, study of sun’s atmosphere during, 2 Efficiency, weather conditions and human, 216; maximum and minimum periods of human, 217, 218 Electricity, and atoms, 31; a manifestation of solar energy, 49 Electron, nucleus of all atoms, 31 Elements, nuclei of atoms of various, 31, 32