Sympathetic vibration, 22 et seq., 379.

Tailor, nature like a covetous, 9-10.

Tangent, the word, 263.

Taste, doubtful cultivation of, by the cla.s.sics, 352-353; of the ancients, 353.

Taylor, on the vibration of strings, 249.

Teaching, its nature, 366 et seq.

Telegraph, the word, 263.

Telescope, 262.

Telestereoscope, the, 84.

Temperament, even, in tuning, 47.

Temperature, absolute, 162; differences of, 205; differences of, viewed as level surfaces, 161; heights of, 174; scale of, derived from tensions of gases, 174.

Terence, 347.

Terms, scientific, 342-343.

Thales, 259.

Theories, their scope, function, and power, 241-242; must be replaced by direct description, 248.

Thermal, energy, 174, 177; capacity, 123, footnote.

Thermodynamics, 160 et seq.

Thermoelectrometer, Riess's, 133, 169.

Thing-in-itself, the, 200.

Things, mental symbols for groups of sensations, 200-201.

Thomson, James, on the lowering of the freezing-point of water by pressure, 162.

Thomson, W., his absolute electrometer, 127, footnote; on thermodynamics, 162; on the conservation of energy, 165; on the mechanical measures of temperature, 174, footnote; on waste of mechanical energy, 175; also 108, 173, footnote.

Thought, habitudes of, 199, 224, 227, 232; relationship between language and, 329; incongruence between experience and, 206; luxuriance of a fully developed, 58; transformation in scientific, 214-235.

Thoughts, their development and the struggle for existence among them, 63; importance of erroneous, 65; as reproductions of facts, 107.

Thread, the individual a, on which pearls are strung, 234-235.

Tides, 283.

Timbre, 37, 38, 39.

Time, 178, 204, 205, footnote.

Toepler and Foucault, method of, for detecting optical faults, 313 et seq., 320.

Tone-figures, 91.

Tones, 22-47, 99 et seq., 212.

Torsion, moment of, 132.

Torsion-balance, Coulomb's, 109, 168.

Torricelli, on virtual velocities, 150; his law of liquid efflux, 150; on the atmosphere, 273.

Tourist, journey of, work of the inquirer compared to, 17, 29, 30.

Transatlantic cable, 108.

Transformation and adaptation in scientific thought, 214-235.

Transformation of ideas, 63.

Transformative law of the energies, 172.

Translation, difficulties of, 354.

Tree, conceptual life compared to a, 231.

Triangle, mutual dependence of the sides and angles of a, 179.

Triple accord, 46.

Truth, wooed by the inquirer, 45; difficulty of its acquisition, 46.

Tumblers, resounding, 23.

Tuning-forks, explanation of their motion, 22 et seq.

Tylor, 186.

Tympanum, 18.

Type, natural laws likened to, 193; words compared to, 191.

Ulysses, 347.

Understanding, what it means, 211.

Uniforms, do not fit heads, 369.

Unique determination, 181-182.

Unison, 43.

Unit, electrostatic, 111. See Force and Work.

United States, 336.

Universal Real Character, a, 192.

Utility of physical science, 351.

Variation, the method of, in science, 230; in biology, 216.

Velocity, of light, 48 et seq.; of the descent of bodies, 143 et seq.; meaning of, 204; virtual, 149-155.

Verstandesbegriffe, 199.

Vertical, perception of the, 272, 286 et seq.; symmetry, 389.

Vertigo, 285, 290.

Vestibule of the ear, 300.

Vibration, 22 et seq.

Vibration-figures, 91.

Vinci, Leonardo da, 278, 283.

Violent motions, 225.

Virtual velocities, 149-155.

Visibility, general conditions of, 312.

Vision, symmetry of our apparatus of, 96. See Eye.

Visual nerves, 96.

Visualisation, mental, 250.

Volt, the word, 343.

Volta, 127, footnote, 134.

Voltaire, 260.

Voltaire's ingAnu, 219.

Vowels, composed of simple musical notes, 26.

Wagner, Richard, 279.

Wald, F., 178, footnote.

Wallace, 216.

War, and peace, reflexions upon, 309, 335 et seq.

Waste of mechanical energy, W. Thomson on, 175.

Watches, experiment with, 41; in a mirror, 93.

Water, jet of, resolved into drops, 60; free, solid figures of, 8; objects reflected in, 94, 191; possible modes of measurement of, 170.

Watt, 266.

Wealth, the foundation of, 198.

Weapons, modern, 335.

Weber, 108, 306.

Weight of bodies, varies with their distance from the centre of the earth, 112.

Weismann, 216.

Wheatstone, his stereoscope, 73; his pseudoscope, 96; also 59.

Wheel, history and importance of, 61 et seq.

Whewell, on the formation of science, 231.

Whole, the, 204, footnote.

Why, the question, 199, 223.

Will, Schopenhauer on the, 190; man's most familiar source of power, 243; used to explain the world, 186; forces compared to, 254; compared to pressure, 14.

Windmill, a rotating, 53.

Wire frames and nets, for constructing liquid figures of equilibrium, 4 et seq.

Witchcraft, 187.