Erman, professor, his opinion of the effects of the voltaic circuit, 340. Euler, his improvement on Newton’s theory of sound, 247. Experience, source of our knowledge of nature’s laws, 76. Experiment, a means of acquiring experience, 76. Utility of, 151. Facts, the observation of, 118. Faujas de St. Fond, imaginary craters of, 131. Fluids, laws of the motion of, 181. Compressibility of, 225. Consideration of the motions of, more complicated than that of equilibrium, 235. Force, analysis of, 86. The cause of motion, 149. Phenomena of, 221. Molecular forces, 245. Fourier, baron, his opinion that the celestial regions have a temperature, independent of the sun, not greatly inferior to that at which quicksilver congeals, 157. His analysis of the laws of conduction and radiation of heat, 317. Franklin, Dr., his experiments on electricity, 332. Fresnel, M., his mathematical explanation of the phenomena of double refraction, 32. His improvement on lenses for lamps of lighthouses, 56. His opinions on the nature of light, 207. His experiments on the interference of polarized light, 261. His theory of polarization, 262. Friction, a source of heat, 313. Galileo, celebrity of, for his knowledge of science, 72. His exposition of the Aristotelian philosophy, 110. His refutation of Aristotle’s dogmas respecting motion, his persecution in consequence of it, 113. His knowledge of the accelerating power of gravity, 168. His knowledge of the weight of the atmosphere, 228. Galvani, utility of his discoveries in electricity, 335. His application of it to animals, 336. Gay-Lussac, his examination of gases and vapours, 319. Generalization, inductive, 1, 90. Geology, 281. Its rank as a science, 287. Geometry, axioms of, an appeal to experience, not corporeal, but mental, 95. Gilbert, Dr., of Colchester, his knowledge of magnetism and electricity, 112. Gravitation, law of, a physical axiom of a very high and universal kind, 98. Influence of, decreases in the inverse ratio of the square of the distance, 123. Greece, philosophers of, their extraordinary success in abstract reasoning, and their careless consideration of external nature, 105. Their general character, 106. Philosophy of, 108. Grimaldi, a jesuit of Bologna, his discovery of diffraction, or inflection of light, 252. Guinea and feather experiment, 168. Gunpowder, invention of, 55. A mechanical agent, 62. Haarlem lake, draining of, 61. Harmony, sense of, 248. Head, captain, anecdote of, 84.