Part 49

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 glasses 313.

Hydrogen balloon, 199.

Hydrostatics, Stevinus's principle of, 141.

Hypotheses, their rôle 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 constitutes 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 classics, mathematics, and sciences, 338-374; limitation of matter of, 365 et seq.

Insulators, 130.

Integrals, 195.