Hoarfrost, i, 121, 258, 374 Hoatzin, xii, 241 "Hobble-Skirt" Cars, vii, 184 Hoe Printing Press, v, 301, 379, 381 Hoffmann, Friedrich, x, 85-6 Hogs, descent of, xii, 310; embryological development, xv, 54, 55; feeding garbage to, viii, 330 Hohenbergia, leaves, xiii, 106 Hohenheim, Aureolus von (see Paracelsus) Hoists, in power plants, vi, 353 Holland, commercial history, xiv, 262, 280-1, 310; low elevation of, 247; rain-deposited salt, i, 60; vaccination in, x, 103; windmills, i, 37; Zuider Zee of, xiv, 45-6 Holland Submarine, v, 382 Holly, American, xiii, 367 Holmes, Dr. Oliver Wendell, x, 114; anesthetics named by, 125; "goodly company" of, 134; puerperal fever studies, 114-15, 122; quoted, on therapeusis, 75 Holmium, symbol and atomic weight, viii, 383 Holothurians, xii, 23 Holyoke, Mount, xiv, 111 Home, electrical appliances in, iv, 10, vii, 73-90; electric wiring, 67-8; lighting and lighting systems, vi, 274-8, vii, 68-72, 75 Homer, historic value of poems, xv, 323-4; medical references in, x, 16-17; on blood showers, i, 55; on the loadstone, vi, 29 Hominy Block, xv, 238-9 Homogeneous Rivers, xiv, 154 Honey, as food, ix, 292; purpose in flowers, xiii, 124, 126, 142-3, 184; "showers" of, i, 357 Honeydew, on plants, i, 351-2, 357 Honeysuckle, Italian, fertilization, xiii, 142-3; leaf arrangement, 38; tendril movement, 111 Hood, Mount, beauty of, xiv, 315; cone of, iii, 226, xiv, 100-1, 225 "Hoodoo Country," xiv, 105 Hoofed Animals, xii, 300-31; evolution, iii, 299, 300 Hooke, balance spring invention, v, 65; geological work, xvi, 126; light theory, 137; microscope invention, x, 67; microscopic work, xvi, 112; on protoplasm, 166 Hooker Telescope, ii, 148, 156, 157-8, 159-60 Hookworm, campaign against, x, 171, 174-5; parasite of, 199, 201; in tropics, xiv, 357 Hookworm Anemia, x, 337 Hoosac Tunnel, drills in building, i, 27 Hope, physical effects, xi, 339 Hopkins, Dr. A. D., i, 255, 256, 367 Hop-vines, xiii, 27, 111 Horizontal Rainbows, i, 177 Hormones, ix, 170, 171, 189, 303, x, 320, 331, 347; disease poisons as, ix, 178 Hornbeam, family, xiii, 193; European, 271-2 Horneblende, iii, 321; chemistry of, viii, 193 Horned Screamers, xii, 256-7 Horned Toad, xii, 204, 206 Horner, William, x, 116 Horn Gaps, vii, 17-18 Horns, in cattle family, xii, 324-5, 328; of deer, 316 Horns (musical), from shells, xii, 74; origin of, xv, 317; sound production by, iv, 239-41 Horrocks, Jeremiah, ii, 58 Horseback Riding, as exercise, x, 304, 317 Horsechestnut Tree, dense shade, xiii, 86; in landscaping, 271-2; leaf-bud protection, 34; stipules absent, 34 Horse Latitudes, i, 129, 374, xiv, 349