Notes, musical, iv, 206-9, xi, 105-6; of Indian scale, xv, 311; pitch and intervals, iv, 205-6, ix, 99-100; pitch changes by motion, iv, 210; quality of, to what due, 233 Notochord, xii, 128; in lancelets, 129 Novae, or New Stars, ii, 331-3; explanation, 329; in class of variables, 324; location, 328; outbursts, 328-9 Nova Scotia, coal beds, iii, 199; Vineland as, xiv, 261 Nuclei, chemical, xvi, 162 Nuggets, iii, 367 Numbers, development of systems of, xv, 180-4; Pythagorean theory, xvi, 80 Numerals, Arabic, xvi, 103; Babylonian, 60-1 Nummulites, iii, 235 Nut Butter, source, xiii, 10, 220 Nuthatches, xii, 268 Nutmeg, xiii, 261-2 Nutrition, chemistry of, viii, 348-72; defective, due to under-chewing, ix, 228; deficiency of, disease from, x, 255-68, 314; problem of, in therapy, 382; stimulated by light, 253 (see also Diet, Food) Nuts, food value, viii, 366; oil in, 246 Nymphs (aquatic larvæ), xii, 106 Oak-Hazel Copses, xiii, 369-70 Oak Trees, antiquity, xiii, 324-5; family, 193; fertilization, 148; flowers without petals, 190; index plants, i, 255; in American forests, xiv, 373; in Danish Peat bogs, xv, 87; in landscaping, xiii, 271-2; northern limit, 367; rate of increase of, xv, 19, 21 Oaths, judicial, xv, 373-4 Oats, food value, viii, 364; native of Old World, xiii, 182; vitamines in, x, 262 Obelisks, Egyptian, ii, 24 Obesity, x, 272-5 Obsequent Streams, xiv, 160, 174 Observatories, ancient, ii, 37, 38, 39; mountain, 139-51; first European, xvi, 100 Occupational Diseases, x, 244-6 Occupational Fatigue, xi, 270 Occupational Postures, xi, 371, 372