Part 60

Puzzle-lock, a, 26.

Puzzles, 277.

Pyramid of oil, 6.

Pythagoras, his discovery of the laws of harmony, 32, 259.

Quality of tones, 36.

Quantitative investigation, the goal of, 180.

Quantity of electricity, 111, 118, 119, 167-170, 173; of heat, 166, 167-171, 174, 177, 244; of motion, 184.

Quests made of the inquirer, not by him, 30.

Quételet, 15, footnote.

Rabelais, 283.

Raindrop, form of, 3.

Rameau, 34.

Reaction and action, principle of, 191.

Reactions, disclosure of the connexion of, 270 et seq.

Realgymnasien, 365.

Realschulen, 365, 373.

Reason, stands above the senses, 105.

Reflex action, 210.

Reflexion, produces symmetrical reversion of objects, 93 et seq.

Refraction, 29, 193, 194, 208, 230, 231.

Reger, 328.

Reliefs, photographs of, 68.

Repetition, its rôle in æsthetics, 89, footnote, 91 et seq., 97, 98 et seq., 390.

Reproduction of facts in thought, 189, 193, 198, 253.

Repulsion, electric, 109 et seq., 168.

Research, function of experimental 181; the aim of, 205.

Resemblances between facts, 255.

Resin, solution of, 7.