Folded Mountains, iii, 131-8, 190-1, xiv, 36-7, 226-34; ridges in, 93-4, 95-6 Folding of Rocks, iii, 84-6, 349 (fig.), 379, xiv, 36; theories of process, 231-2; topography made by, 38, 93-9 Food, Foods, adulteration of, viii, 370-1; amount consumed, 366-7; artificially prepared, x, 257, 267-8; benzenes and paraffins as, viii, 234; calories in various, 361, ix, 299, x, 269; calories, valuation in, iv, 48; chemistry of, viii, 348-72; children's, x, 314-15; cold storage of, iv, 187, 8; constituents all in air and water, i, 25; cooking of, viii, 367-9, x, 263, 266 (see Cooking); deficiency of, diseases from, x, 255-69, 276; digestion and utilization, viii, 356-9, ix, 226-52, 277-304, x, 268-71, 319-20; fat-producing, x, 273; infants', ix, 346-7; kinds needed during exertion, xi, 278; methods of obtaining, importance of, xv, 186-7; nitrogen importance, viii, 66, 229; of animals and plants, 349, 350, xii, 15; procuring of, by animals, ix, 18-20 (see also Chemotaxis); requirements, viii, 362-7, 369-70, x, 255-68, 278-9; selection of, viii, 369, ix, 300-1; sources of, 24-30; storing of, by animals, xii, 292-3; taste and smell of, ix, 94-5, 97-8, 240, 241-2; use of, for energy development, 15-16, 24, 36-40, 289-301; use of, for growth, 31-4, 38-9, 286-9; use of, for tissue repair, 34-6, 278-84 (see also Diet, Nutrition) Food-poisoning, indigestion from, ix, 239 Food Plants, xiii, 209-27 Food Preserving, viii, 371-2; chilling and refrigeration, v, 346, 353; X-ray sterilizing, vii, 257 Food Supply, its making by plants, xiii, 77-84, 95, 96; of tropics, 359 "Fool's Gold," iii, 335 Foot Candle, iv, 352, vii, 368 Foot-pound, iv, 79, vi, 82; erg and calorie equivalents, vii, 382; equivalent in watt-hours, iv, 312; heat equivalent, v, 350-1 Foot-pound-second System, iv, 46 (see British System) Foot-poundal, unit of work, iv, 79 Foraminifers, iii, 54, 259, 261, 266; in pelagic plankton, xii, 17-18 Force (mechanics), iv, 33-4, 41; centrifugal and centripetal, 71-5; defined, v, 182-3; law of, in machines, iv, 90, 92; Leibnitz's theory, xvi, 117; magnetic, vii, 369; measurement and units of, iv, 46, 58, 63-5, 69-70; momentum and, 66-7; motion and, 56-69, 71-2, 78; Newton's and Huygens' studies of, 11; primary forms of, 25; static and kinetic measures of, 33; work in relation to, 37-8, 78-9 Force Pump, v, 113-14 Forces, composition and resolution of, iv, 75-7; parallel, 99; parallelogram of, v, 184-6 Forecasts, i, 224 (see Weather Forecasts, Crop Forecasts) Foreign Languages, advantages of learning, xv, 146; jabbering sound, xi, 103; difficulty of learning, 201 Foreign Plants, importation forbidden, xiii, 272, 289; introduction aided by phenology, i, 254