Plans, geodesic experiments in Lombardy, 168.
Planets, 89-99; present number discovered, 90. (See note by Translator on the most recent discoveries, 90, 91); Sir Isaac Newton on their composition, 132; limited physical knowledge of, 156, 157; Ceres, 64-92; Earth, 88-99; Juno, 64, 92-97, 106; Jupiter, 64, 87, 92-98, 202; Mars, 87, 91-94, 132; Mercury, 87, 92-94; Pallas, 64, 92; Saturn, 87, 92-94; Venus, 91-94, 202; Uranus, 90-94; planets which have the largest number of moons, 95, 96.
Plants, geographical distribution of, 346-350.
Plato on the heavenly bodies, etc., 69; interpretation of nature, 163; his geognostic views on hot springs, and volcanic igneous streams, 237, 238.
Pliny the elder, his Natural History, 73; on comets, 104; aerolites, 122, 123, 130; magnetism, 180; attraction of amber, 188; on earthquakes, 205, 207; on the flame of inflammable gas, in the district of Phasells, 223; rarity of jasper, 261; on the configuration of Africa, 292.
Pliny the younger, his description of the great eruption of Mount Vesuvius, and the phenomenon of volcanic ashes, 235.
Plutarch, truth of his conjecture that falling stars are celestial bodies, 133, 134.
Poisson on the planet Jupiter, 64; conjecture on the spontaneous ignition of meteoric stones, 118; zodiacal light, 141; theory on the earth's temperature, 172, 173, 174, 176, 177.
Polarization, chromatic, results of its discovery, 52; experiments on the light of comets, 105, 106.
Polybius, 291.