Physical data, necessity of, 209. Great importance of, 211. Illustrated by the erection of observatories, 213. Necessity of an exact knowledge of, 214. More precise than the observations by which we acquire them, 215. Physics, axioms of; analysis of, 102. Planets, circumjovial, 186. Platina, discovery of, 308. Pliny, his knowledge of quartz and diamond, 239. Pneumatics, 228. Political economy, 73. Prejudices of opinion and sense, 80. Conditions on which such are injurious, 81. Illustrated by the division of the rays of light, by the moon at the horizon, and by ventriloquism, 82. By the transition of the hand from heat to cold, 83. Prevost, M., his theory of heat, 316. His theory of reciprocal interchanges, a proof of the radiation of cold, 318. Printing, the art of, 193. Performed by steam, 194. Probabilities, doctrine of, 217. Illustrated by shooting at a wafer, 218. Prout, Dr., his opinion of the atomic weights, 307. Pyrometry, 319. Pythagoras, philosophy of, 107. Quinine, sulphate of, comparative comfort and health resulting from the use of, 56. Radiation of heat, laws of, 205. Repulsion in fluids and solids, 227. Rules, general, for guiding and facilitating our search among a great mass of assembled facts, 151. Rumford, count, experiments of, on gunpowder, 62. Savart, M., his experiments on solids, 243. His researches on sound, 249. Science, abstract, a preparation for the study of physics, 19. Not indispensable to the study of physical laws, 25. Instances illustrative of, 27. Science, physical, nature and objects, immediate and collateral, as regarded in itself and in its application to the practical purposes of life, and its influence on society, 35. State of, previous to the age of Galileo and Bacon, 104. Causes of the rapid advance of, compared with the progress at an earlier period, 347. Science, natural, cause and effect, the ultimate relations of, 76. Sciences and Arts, remarks on the language, terms, or signs used in treating of them, 70. Receive an impulse by the Baconian philosophy, 114. Sensation, cause of, 91. Senses, inadequate to give us direct information for the exact comparison of quantity, 124. Substitutes for the inefficiency of, 125. Seringapatam, method of breaking blocks from the quarries of, 47. Shells found in rocks at a great height above the sea, supposed cause of, 145. Smeaton, his experiments on bodies dilated by heat, 319. Solids, transparent, exhibit periodical colours when exposed to polarized light, 99. Influence of, on the Mind, 101. Solids in general, nature of, 236. Constitution of, complicated, 237. Toughness of, distinct from hardness; tenacity of, 238. Become liquefied by the addition of heat, 321.