Frogs, iii, 285, xii, 169, 174-6, 177-81; evolution of, 167; heart of, ix, 84; regeneration in, xii, 170; sense organs in, 169, 174; "showers" of, i, 355; temperature effects on, ix, 78-9, 306 Frostbite, x, 252 Frosts, i, 257-60, 373; insurance, 270; rock weathering by, iii, 24, xiv, 62, 75-7, 233 Frost Smoke, i, 95, 373 Fructose, viii, 226 Fruit, defined, xiii, 53-4; development, 54-5; dry and fleshy, 54-5; family groups determined by, 184; flavors due to esters, 221; food value, 365, ix, 34, 300, x, 262, 266, 268, 273, 317; in grasses and sedges, xiii, 179, 182; purposes of, 61; seed dispersal, 55-9 (see also Seed Dispersal); sugar storage in, ix, 27-8 Fruit Trees, as index plants, i, 255-6; frost danger points, 258 Fuels, future motor, viii, 209; heat measurement, 360-1; our waste of, v, 172; power from oxidation of, ix, 15-16, 24 Fuel Value, viii, 360-1 Fuji-san, Japan, xiv, 100, 320 Fujiyama, Japan, as observatory site, ii, 145, 149; shadow in sky, i, 170 Fulgurites, i, 153, 373 Fuller Cells, vi, 137, 142-3 Fully, Lake, water drop, v, 81 Fulminating Mercury, viii, 262 Fulton, Robert, steamboat, v, 192, 377; steam war vessel, 378; submarine, 197-8 Functional Metabolism, ix, 39; control of, 39-40, 77-8, 170; daily amount in calories, 297; food requirements dependent on, 295; heat production by, 307; no tissue wastage by, 282-3; of glands, 159; of muscle cells, 74, 77-9; of nerve cells, 122-3; of posture, 84; of vital processes, 295-6 Fundamental Tones, iv, 213; of bells, 222; of organ pipes, 228-30; of vibrating strings and rods, 223-4 Fundy, Bay of, tides, v, 175, xiv, 293 Fungi, xiii, 70-1; in coal formation, 312; luminous, i, 346; reproductive processes, xiii, 164; in rotten plants, 99; species, 323; spores in atmosphere, i, 61 Fungicides, viii, 77, 333 Funk, Casimer, x, 259 Furs, source of costly, xii, 346-51; warmth of, iv, 178, ix, 311, x, 309 Furrows, of continental shelves, xiv, 287 Fusel Oil, viii, 214 Fuses, purpose and construction, vii, 34-7, 369; inverse time features, 37, 39 Fusibility, of minerals, viii, 202, 384 Fusion, latent heat of, iv, 152, 160, 161; table, 162 Fusions, of odors, xi, 81; of tastes, 73; of tones, 106; of touch, 111 Future, a habit of thought, xi, 192; predictions of, xv, 354, 355 Future Life, primitive conceptions of, xv, 332-6, 339, 340, 345, 358 Gadflies, xii, 120 Gadolinium, symbol and atomic weight, viii, 383 Gailey, James A., v, 383 Galactose, viii, 226 Galagos, xii, 375 Galapagos Islands, xiv, 276; turtles of, xii, 187, 192