Deltas, iii, 32, xiv, 53; alluvial soil of, 70; coasts formed by, 53, 263; in lakes, 202, 210-11; lakes formed by, 203; rivers joined by, 185
Demagnetization, vi, 37-8, 117, vii, 366; by heat, iv, 253; test, vi, 43
Democritus, on knowledge, xvi, 87; on matter, 83; on origin of earth, ii, 366-7
Dendrites, xi, 18, 19; receptors for pain, 117
Denmark, antiquity of man in, xv, 86-7; föhrden of, xiv, 259; forests and peat bogs, xv, 86-7
Density, absolute, iv, 110-11; methods of determining, 111-12; of liquids, how measured, 113, vi, 147; of various substances, iv, 113; specific, 111; standard of, 149
Dentistry, hypnosis in, xi, 316; protection against pain, 121
Department Stores, Christmas lighting, vii, 342; pneumatic tubes in, iv, 130; rain and business, i, 265
Depolarization, of electric cells, vi, 137, 139, vii, 366
Depression, of land and sea areas, (see Subsidence)
Depressions, (geological) in land, xiv, 204-5; in ocean floor, 286
Depressions (meteorological), i, 135, 371 (see Lows)
Depth, perception of, ix, 119-20, xi, 173-85
Descartes, influence of, x, 67; mathematical and scientific work, ii, 15, xvi, 113-14, 118-19; theory of vortices, ii, 60
Descriptive Astronomy, development of, ii, 15-16, 113-14, 119, 139
Deserts, density of air over, i, 171; dust whirls, 60; evaporation in, 323; in trade wind belts, xiv, 355-6, 380; irrigation by sun-power, v, 178; lizards of, xii, 206; mirages, i, 172-3, 174, iv, 328-9; rainfall, i, 112; rainfall and plants, xiii, 377-81; rock weathering in, iii, 23, 71-3, xiv, 42, 77, 79; salt deposits, viii, 197; "stretching" of, xi, 173; water-storing plants, xiii, 28, 30, 41-2, 104, 106-7, 336 (illus.); wind action in, iii, 71-5 (see also Arid Regions)
Design, elements of (prehistoric), xv, 299
Designs, enlargement of by lanterns, iv, 342
Desires, suppression of, xi, 140-2 (see also Suppressions)
Despondency, indigestion and, xi, 370 (see also Dejection)
Detectors, wireless, iv, 315-16, vii, 261, 268-70, 278-80; to guide ships, 284-5
Determiners, inheritance, ix, 329-42, x, 233-4, xiii, 330, xvi, 156
Devil's Tower, Wyoming, iii, 111, 176 (Pl. 10), xiv, 129-30
Devonian Period, iii, 20, 194-6, 378; "Age of Fishes," 283, xv, 71; animals and plants in, iii, 252, 271, 277, 278, 282-4, 285; extension of sea in, 192 (fig. 37)