Horsepower, defined, iv, 80, vi, 83, 84, vii, 369; electrical equivalent, vi, 84-5; erg and calorie equivalents, vii, 382; men's labor in, iv, 311; thermal equivalents, v, 350-1 Horsepower-hours, iv, 80 Horseradish, aconite and, xiii, 252; in mustard family, 197; origin, 223 Horses, xii, 306-7; automobiles and, v, 215; class of, xii, 300; cost of work, vii, 224-6; diphtheria antitoxin from, x, 297; domestication of, xv, 197; ear movements, of, ix, 82, 117; fear in, xi, 136; geological history, iii, 299-300; pictured in ancient art, xv, 112, 114, 116; surra disease of, x, 168; young of, ix, 346 Horseshoe Magnets, iv, 250, vi, 34, 45, 333 Horsetail Plants, iii, 251, 254, 256, xiii, 308-9, 314, 317, 323 Hoses, force, vi, 47-9; rate of flow, 70-1 Hospitals, disease germs of, i, 325-6; rise of modern, xvi, 184; "Sunday temperatures" in, xi, 140 Hospital Tanks, v, 120 Hot Air Heating System, iv, 185 Hot Baths, ix, 322, x, 311-12, 383; after eating, ix, 313; cold sensation on entering, 93; therapeutic uses of, x, 311, 383 Hot Climates, clothing for, x, 307, 308; oiling of skin in, 311 Hot Springs, occurrence and explanation, iii, 128, xiv, 143-5; plant life in, xiii, 299; proof of earth's internal heat, xiv, 12; travertine deposits, 146 Hottentots, hair of, xv, 38; marriage by purchase among, 284 Hot-water Bottle, iv, 162-3 Hot Water Heating System, iv, 185-6, 187 Hot Water Plants, xiii, 299, 300, 301 Hot Waves, i, 374 Hot Winds, i, 134, 374 Hotchkiss Machine Gun, v, 365 Hotels, color lighting, vi, 274-5 House-breaking, of children, xi, 251-2 House Meters, vii, 174-7 Houses, dry air of, xiv, 353; electric wiring, vii, 65-8; evolution of, xv, 266-8 Howard, Luke, i, 97-8 Howe, Elias, sewing machine, v, 284, 379 Howitzers, v, 368-9 Huanacos, xii, 313 Huckleberry, growth of, x, 229 Hudson River, course, iii, 234, 245; estuary of, xiv, 40; locating rock under, v, 263-4; mouth, xiv, 25, 270; Palisades (see Palisades of Hudson); sediment in channel, 268; submerged channel, iii, 37 (fig.), 78, 234, xiv, 25, 287; superimposed stream, iii, 233 Hudson River Valley, drowned character, iii, 38, 77-8, xiv, 25, 40, 255; origin, iii, 232; section of, 138 (fig.) Hue, of colors, xi, 90 Hughes, D. E., vi, 26; coherer of, xvi, 191 Human Energy, consumption in life processes and work, viii, 367; daily expenditure in calories, ix, 297; efficiency in use of, 296, 306; food sources and requirements, viii, 334, 349, 350, 359, 361, ix, 289-301; from foods, calculation of, x, 269-70; per cent used, xi, 264; Ostwald's imperative, 257; production in kinetic system, 60-1 Humanists, "medical," x, 45