Nitrogen, viii, 18, 64-8; agricultural needs and sources, i, 34, vii, 321, viii, 73-4, 75, 280, 340, 341, 343, 345-6, xiv, 64-5, 66; atmospheric, i, 10, 11, 34, vii, 321-2, viii, 67; atomic weight and symbol, 383; boiling and freezing points, iv, 173; chemical inertness, i, 12-13; critical temperature, 29, iv, 173; derivatives, viii, 229-30 (see also Amines); elimination from body, 353-4, x, 342; fixation, natural and artificial, i, 13, 33, 34-7, 153, vii, 301, 321-4, 352-3, viii, 66, 73-5, 153, 345-6, x, 193-4, xiii, 98, xiv, 66, xvi, 165; freed by combustion and decay, viii, 61, 330, 345-6; in blood effects, i, 329, v, 120, x, 346; in chlorophyll, xiii, 80; in explosives, viii, 63, 345-6; in garbage, 330; in proteins, 64-5, 340, 351, ix, 29, 279, 282, 284, x, 270, 277; industrial uses, i, 33, 34; liquefaction of, iv, 171; melting point, 162; preparation from air, viii, 65-6; production from liquid air, i, 30, 32, 34, viii, 67, 68, 274; solubility in water, 40, 111; spectrum of, i, 161 Nitrogen Compounds, viii, 64, 68-74; by-products of coke, 46-7; in air, i, 13; in animal body, viii, 353-4; instability, 66; organic, 229-30; vitamines, 369 Nitrogen Cycle, viii, 73, 334, 335, 349; practical applications, 325-6, 330, 340, 345-6 Nitrogenous Waste, x, 270 Nitroglycerine, viii, 63, 247-8, 260, 261 Nitrous Acid, viii, 115; in atmosphere, i, 13; production, 36 Nitrous Oxide, viii, 70-1; as anesthetic, x, 123-4; critical temperature and pressure, iv, 172 Nobody Crabs, xii, 89 Noctilucent Clouds, i, 17-18, 58, 377 Nodes, of moon, ii, 197 Nodes, of vibrations, iv, 217 Noguchi, Hideyo, x, 173 Noises, awe roused by, xi, 147; qualities of, 104 Nomadic Life, xv, 128, xiv, 141 Nonconductors, (electrical) iv, 259, vi, 77, 294, vii, 373; nonmetals as, viii, 126 Nonmetals, viii, 17-19, 84, 126, 379; in body tissues, 354; manufacture and uses, 274-5; negative ionization, 122; oxides of, 20, 39; periodic classification, 181; plants needs of, 337, 341; tests, 289-90; union with metals, 20, 32 Nordic Group, xvi, 48-9, 50 Norfolk, Va., harbor of, xiv, 268 Noria, ancient use of, v, 19 Normals, meteorological, i, 204, 378 North Africa, civet cat of, vii, 353; civilization in, xiv, 196; mormoids of, xii, 154; vultures of, 260; zoölogy of, xiv, 291