Nolan, 376.

Non-Euclidean geometry, 38, 300–307.

Nonius, 153; ref. to, 154.

Notation: in algebra, 15, 75, 93, 133, 134, 149, 150, 151, 160, 167; Babylonian numbers, 5–7; Egyptian numbers, 13; Greek numbers, 64; Arabic notation, 3, 73, 87, 102, 112, 127–129, 159; Roman, 78; decimal fractions, 160; trigonometry, 249; differential calculus, 205, 221, 222, 260, 269, 283. See Exponents, Algebra.

Nöther, 311, 313, 330, 356.

Numbers: amicable, 68, 108, 115; excessive, 68; heteromecic, 68; perfect, 68; defective, 68; triangular, 180; definitions of numbers, 372; theory of numbers, 55, 76, 95, 108, 119, 131, 178–182, 252, 264, 280, 362–372.

Numbers of Bernoulli, 238.

Numerals: Egyptian, 13; Babylonian, 5–7; Greek, 64; Arabic, 87, 102, 103, 112. See Apices.

Oberbeck, 386.

Œnopides, 19; ref. to, 16.

Ohm, M., 317.

Ohrtmann, X.

Olbers, 364, 373.

Oldenburg, 228.

Olivier, 300.

Omega-function, 353.

Operations, calculus of, 292.

Oppolzer, 377.

Optics, 39.

Oresme, 134; ref. to, 160.

Orontius, 154.

Oscillation, centre of, 191, 243.

Ostrogradsky, 333, 379.

Otho, 142.

Oughtred, 167; ref. to, 147, 161, 202.

Ovals of Descartes, 187.

${\displaystyle \scriptstyle {\pi }}$: values for; Babylonian and Hebrew, 8; Egyptian, 11; Archimedean, 41; Hindoo, 98; Arabic, 108; Ludolph's, 154; Wallis', 194, 195; Brouncker's, 197; Fagnano's, 241; Leibniz's, 220; selection of letter ${\displaystyle \scriptstyle {\pi }}$, 250; proved to be irrational, 259, 281; proved to be transcendental, 2.

Pacioli, 135; ref. to, 134, 142, 152, 155, 158, 196.

Padmanabha, 87.

Palatine anthology, 73, 120.

Pappus, 58–61; ref. to, 35, 39, 45, 49, 50, 55, 65, 66, 153, 178, 186.

Parabola, 42, 70, 198; semi-cubical, 190. See Geometry.

Parabolic geometry. See Non-Euclidean geometry.

Parallelogram of forces, 183.

Parallels, 38, 281, 300, 301, 303, 306.

Parameter, 48.

Partial differential equations, 208, 255, 287, 341 et seq., 379.

Partition of numbers, 372.

Pascal, 175–177; ref. to, 178, 182, 196, 220, 240, 284, 285, 290, 310.

Pascal's theorem, 178.

Peacock, 284; ref. to, X., 130, 133, 161, 283, 315.

Pearson, 391.

Peaucellier, 326.

Peirce, B., 323; ref. to, 291, 317, 376, 381.

Peirce, C. S., 323; ref. to, 37, 307, 321.

Peletarius, 166.

Pell, 147, 151, 181, 219.

Pell's problem, 97, 181.

Pemberton, 201.

Pendulum, 191.

Pepin, 365.

Perier, Madame, X.

Periodicity of functions, 349, 350.

Pernter, J. M., 385.

Perseus, 50.

Perspective, 177. See Geometry.

Perturbations, 273.

Petersen, 365.

Pfaff, 341, 342; ref. to, 362.

Pfaffian problem, 341, 342.

Pherecydes, 20.

Philippus, 33.

Philolaus, 22; ref. to, 28, 68.

Philonides, 46.

Physics, mathematical. See Applied mathematics.

Piazzi, 373.

Picard. E., 347, 350, 360.

Picard, J., 214, 215.

Piddington, 384.