Pascal takes a barometer up the Puy de Dome, 17. Pennsylvania fireplace invented by Franklin, 63; _Gazette_ published by Franklin, 53. Perpetual motion, Rumford's contrivances for, 150; impossibility of, 322. Philadelphia, Franklin's first arrival in, 46; Library, foundation of the, 55. Photometer, Rumford's, 187. Pigments, effects of mixing, 217. Points _versus_ knobs, 95, 131. Polarization, explained by transverse vibrations, 226; of light discovered by Malus, 226. "Poor Richard's Almanack," 60. Pressure of the air the cause of suction, 29. R. Radiation, Rumford's experiments on, 184; of cold, Rumford's experiments on, 186. Rede Lecture, delivered by Clerk Maxwell, 293. Refraction of light, laws of, 1; mentioned by Pliny, 1. Relative economy of different sources of light, 188. Resistance of conductors, Cavendish's experiments on, 142. Roemer, measurement of the velocity of light by, 2. Rosetta Stone, discovery of the, 234; inscription on, 234. Royal Institution, foundation of the, 169; Young's lectures at the, 212; Faraday's appointment at the, 245; Maxwell's lecture on colour at the, 287. Royal Society, origin of the, 13-15. =Rumford=, Count, birth and parentage, 148; life as a medical student, 153; becomes a schoolmaster at Concord, 154; marriage, 154; summoned before the Committee of Safety, 156; imprisoned at Woburn, 156; first journey to London, 158; receives an appointment in the Colonial Office, 158; experiments on the explosion of gunpowder, 158, 179; elected F.R.S., 158; made lieutenant-colonel in the British army, 159; promoted to colonel, 160; visits Elector of Bavaria, 160; cured of martial ambition, 160; enters the service of the Elector of Bavaria, 161; knighted by George III., 161; reforms in the Bavarian army, 162; attack on the beggars, 163; made Count of the Holy Roman Empire, 165; robbed of his manuscripts, 166; visited by his daughter, 166; his roaster, 166; experiments on fire-places, 166; founds the Rumford Medal, 167; appointed Minister Plenipotentiary to the Court of Great Britain, 169; founds the Royal institution, 169; plans for the Institution, 169; residence in Paris, 175; marriage with Madame Lavoisier, 175; death; 176; Cuvier's _eloge_ on, 176; statue at Munich, 178; experiments on the conduction of heat in fluids, 181; on the convection of heat in viscous liquids, 184; on the weight of heat, 185; on radiation, 185; on the conduction of heat, 186; on the apparent radiation of cold, 187; shadow-photometer, 188; experiments on the relative economy of candles and tapers, 188; on the traction of carriages, 189;