Part 42

D'Alembert, on the causes of harmony, 34; his principle, 142, 149, 154; also 234, 279.

Danish schools, 338, footnote.

Darwin, his study of organic nature, 215 et seq.; his methods of research, 216.

Deaf and dumb, not subject to giddiness, 299.

Deaf person, with a piano, analyses sounds, 27.

Death and life, 186.

Definition, compendious, 197.

Deiters, 19.

Delage, 298, 301, 302.

Democritus, his mechanical conception of the world, 155, 187.

Demonstration, character of, 362.

Deportment of the energies, conformity in the, 171-175.

Derivation, laws only methods of, 256.

Descent, Galileo's laws of, 193; generally, 143 et seq., 204, 215.

Description, 108, 191, 236, 237; a condition of scientific knowledge, 193; direct and indirect, 240; in physics, 197, 199.

Descriptive sciences, their resemblance to the abstract, 248.

Determinants, 195.

Diderot, 234.

Dielectric constant, the, 117.

Difference-engine, the, 196.

Differential coefficients, their relation to symmetry, 98.

Differential laws, 204.

Differential method, for detecting optical imperfections, 317.

Diffraction, 91, 194.

Diffusion, Fick's theory of, 249.

Discharge of Leyden jars, 114 et seq.

Discoveries, the gist of, 270, 375.

Discovery and invention, distinction between, 269.