Hat, a high silk, 24.

Hats, ladies', development of, 64.

Head-wave of a projectile, 323 et seq.

Hearing and orientation, relation between, 304 et seq.

Heat, a material substance, 177; difference between the conceptions of electricity and, 168 et seq.; substantial conception of, 243 et seq.; Carnot on, 156, 160 et seq.; Fourier on the conduction of, 249; not necessarily a motion, 167, 170, 171; mechanical equivalent of, 164, 167; of liquefaction, 178; quant.i.ty of, 166; latent, 167, 178, 244; specific, 166, 244; the conceptions of, 160-171; machine, 160; a measure of electrical energy, 133 et seq.; mechanical theory of, 133; where does it come from? 200.

Heavy bodies, sinking of, 222.

Heights of ascent, 143-151.

Helm, 172.

Helmholtz, applies the principle of energy to electricity, 184; his telestereoscope, 84; his theory of Corti's fibres, 19 et seq.; on harmony, 35, 99; on the conservation of energy, 165, 247; his method of thought, 247; also 138, 305, 307, 375, 383.

Hensen, V., on the auditory function of the filaments of Crustacea, 29, 302.

Herbart, 386 et seq.

Herbartians, on motion, 158.

Herculaneum, art in, 80.

Heredity, in organic and inorganic matter, 216, footnote.

Hering, on development, 222; on vision, 210.

Hermann, E., on the economy of the industrial arts, 192.

Hermann, L., 291.

Herodotus, 26, 234, 347, 350.

Hertz, his waves, 242; his use of the phrase "prophesy," 253.

Herzen, 361, footnote.

Hindu mathematicians, their beautiful problems, 30.

Holtz's electric machine, 132.

Horse, 63.

Household, physics compared to a well-kept, 197.

Housekeeping in science and civil life, 198.

Hudson, the, 94.

Human beings, puzzle-locks, 27.

Human body, our knowledge of, 90.

Human mind, must proceed economically, 186.

Humanity, likened to a polyp-plant, 235.

Huygens, his mechanical view of physics, 155; on the nature of light and heat, 155-156; his principle of the heights of ascent, 149; on the law of inertia and the motion of a compound pendulum, 147-149; on the impossible perpetual motion, 147-148; on work, 173; selections from his works for use in instruction, 368; his view of light, 227-228, 262.

Huygens, optical method for detecting imperfections in optical gla.s.ses 313.

Hydrogen balloon, 199.

Hydrostatics, Stevinus's principle of, 141.

Hypotheses, their rAle in explanation, 228 et seq.

Ichthyornis, 257.

Ichthyosaurus, 63.

Idea? what is a theoretical, 241.

Idealism, 209.

Ideas, a product of organic nature, 217 et seq.; and facts, necessary to science, 231; not all of life, 233; their growth and importance, 233; a product of universal evolution, 235; the history of, 227 et seq.; in great minds, 228; the rich contents of, 197; their unsettled character in common life, their clarification in science, 1-2.

Ideography, the Chinese, 192.

Imagery, mental, 253.

Imagination, facts reflected in, 220 et seq.

Inclined plane, law of, 140-141.

Incomprehensible, the, 186.

Indian, his modes of conception and interpretation, 218 et seq.

Individual, a thread on which pearls are strung, 234-235.

Industrial arts, economy of the, E. Hermann on, 192.

Inertia, law of, 143 et seq., 146 et seq., 216, footnote, 283 et seq.

Innate concepts of the understanding, Kant on, 199.

Innervation, visual, 99.

Inquirer, his division of labor, 105; compared to a shoemaker, 105-106; what const.i.tutes the great, 191; the true, seeks the truth everywhere, 63 et seq.; the, compared to a wooer, 45.

Instinctive knowledge, 189, 190.

Instruction, aim of, the saving of experience, 191; in the cla.s.sics, mathematics, and sciences, 338-374; limitation of matter of, 365 et seq.

Insulators, 130.

Integrals, 195.

Intellectual development, conditions of, 286 et seq.

Intentions, acts of nature compared to, 14-15.

Interconnexion of nature, 182.

Interdependence, of properties, 361; of the sensuous elements of the world, 179.

Interference experiments with the head-wave of moving projectiles, 327-328.

International intercourse, established by Latin, 341.

International measures, 108.

Invention, discovery and, distinction between, 269.

Inventions, requisites for the development of, 266, 268 et seq.

Iron-filings, 220, 243.

Italian art, 234.

Jacobi, C. G. J., on mathematics, 280.

James, W., 275, 299.

Java, 163.

Jews and Christians, monotheism of the, 187.

Jolly, Professor von, 112, 274.

Joule, J. P., on the conservation of energy, 163-165, 167, 183; his conception of energy, 245; his metaphysics, 183, 246; his method of thought, 247; also 137, 138.

JournAe, 317.

Judge, criminal, the natural philosopher compared to a, 48.

Judgment, essentially economy of thought, 201-202; sharpened by languages and sciences, 357-358; also 232-233, 238.

Juliet, Romeo and, 87.

Jupiter, its satellites employed in the determination of the velocity of light, 51 et seq.

Jurisprudence, Latin and Greek unnecessary for the study of, 346, footnote.

Kant, his hypothesis of the origin of the planetary system, 5; his Critique of Pure Reason, 188; on innate concepts of the understanding, 199; on time, 204; also footnote, 93.

Kepler, 187, 270.

Kinetic energy, 177.

Kirchhoff, his epistemological ideas, 257-258; his definition of mechanics, 236, 258, 271, 273.

Knight, 289.

Knowledge, a product of organic nature, 217 et seq., 235; instinctive, 190; made possible by economy of thought, 198; our first, derived from the economy of self-preservation, 197; the theory of, 203; our primitive acts of the foundation of science, 190.

Kocher, 328.

Koenig, measurement of the velocity of sound, 57 et seq.

KAlliker, 19.

Kopisch, 61.

Kreidl, 299, 302, 306; his experiments, 272.

Krupp, 319.

Labels, the value of, 201.

Labor, the acc.u.mulation of, the foundation of wealth and power, 198; inquirer's division of, 105, 258.

Labyrinth, of the ear, 18, 291, 305.

Lactantius, on the study of moral and physical science, 89.

Ladder of our abstraction, the, 208.

Ladies, their eyes, 71; like tuning-forks, 23-24.

Lagrange, on Huygens's principle, 149; on the principle of virtual velocities, 150-155; character of the intellectual activity of a, 195, 278.

Lake-dwellers, 46, 271.

Lamp-shade, 70.