Human Life, temperate zones most favorable, xi, 51; temperature limits, v, 348, ii, 243 (see also Life) Human Race, cradle of, xvi, 46-7; grouping tendency of, x, 9; improvement by selection, xvi, 157 Humanistic Period, xvi, 86 Human Voice, range of, ix, 99 (see Voice) Humboldt, Alexander von, discovery of orchid insect, xiii, 48; geological work, xvi, 170, 171; on the Ghor of Syria, xiv, 121; on thunder at sea, i, 193; studies of electric eel, vi, 16 Humboldt Current, xiv, 305 Humboldt Range, iii, 214 Humidifying Systems, i, 78 Humidity, i, 76, xiv, 353-4; absolute and relative, i, 76-7, 375, xiv, 352-3, 354; atmospheric, viii, 67; body heat and, i, 317, v, 348-9, ix, 316, 317, x, 237, 251, xiv, 354; danger in thunderstorms, i, 156; heat prostration from, ix, 316; measurement of, i, 78-9; practical importance, 77-8; ventilation and, 321, viii, 331, 332, ix, 268-9, 270, x, 237 Hummingbirds, xii, 269; colors of, 245; family of, 267; plant fertilization by, xiii, 144 Humor, psychology of, xi, 350-7 Humoral Doctrine, x, 21, 28-9, 69, 98, 380 Humped Cattle, xii, 330 Humphreys, Dr. W. J., i, 58, 59, 113, 152, 153, 155, 172 Humus, formation of, viii, 340, 341, 346-7 Hungary, loess deposits, xiv, 72; plains of, xiii, 373, xiv, 217; stone implements of ancient, xv, 109 Hunger, "best sauce," ix, 242; food regulation by, 299; impulse of, in civilization, xv, 185-204, 273; sensation of, ix, 87-8, 231, xi, 65-6, 67, xv, 65; sense of, in infants, ix, 349-50; sleep and, xi, 290 Hunger Strikes, water in, x, 275 Hunt, T. Sterry, xvi, 190 Hunter, John, x, 93-6, 97; electric eel studies, vi, 16; Jenner pupil of, x, 94, 99; Virchow compared to, 129 Hunter, William, x, 92-3, 94 Hunter's Moon, ii, 196 Hunting, primitive methods and devices, xv, 222-8 Hunting Dog, African, xii, 345 Hunting Dogs, heart in, x, 332 Hunting Stage, xv, 187, 192-6; equality of members in, 376; leaders in, 366; polygamy in, 287 Hurdy-Gurdy Wheel, v, 77 Huron, Lake, size, xiv, 204 Hurricane Cliffs, xiv, 124 Hurricane Grass, xiii, 344 Hurricanes, i, 136, 375; electrification by, vii, 212-13; handling of ships in, i, 277-8; warnings in Caribbean Sea, 282, 309 Hurry, modern spirit of, xv, 12 Hussey, Obed, v, 244-5, 246, 247, 249, 379 Hutton, Dr. James, geologist, xvi, 126, 169-70 Huxley, gorilla studies of, xv, 57; on herring, xii, 156; work of, x, 136, xvi, 140-1, 142, 182 Huygens, as astrologer, ii, 21; Kepler's Laws and, 61; light theory, xvi, 119; mechanical method of, iv, 11; micrometer invention, ii, 58; on planetary pull, 63; on rings of Saturn, 54, 57; pendulum clock invention, v, 65; studies of Mars, ii, 227, 228; studies of nebulæ, 357; telescopes, 13, 57, 99 Hyacinth, xiii, 120, 184