PACIFIC, volcanoes in, 229 Palmieri, Professor, cited, 25, 37 Papandayang, eruption of, 169 Papin's digester, nature of action in, 22 _Parasitic cones, formation of_, 161, 162, fig. 61 Pele's Hair, 71 Perlitic structure, 109 Phillips, Mr. J. A., cited, 220 Phonolites, 50, 59 Phonolite-volcanoes, 126 _Photograph of Vesuvius eruption_, 24, fig. 5 'Pine-tree, appendage of Vesuvius, 29 Pitchstones, porphyritic, 60 Plateaux formed of lava-sheets, 270 Pliny, Elder, death of, 7 Plombières, hot springs of, 147 Plutonic rocks, 61 Pompeii, nature of materials covering, 117 Ponza Islands, 39 _Ponza, sections in_, 131, 132, figs. 51, 52 Porphyrites, 263 Porphyritic pitchstones, 60 Potentially liquid rock, 250 Pre-Cambrian volcanoes of British Islands, 274 Presence of water in lavas, 353 Pressure under which crystals were formed, 65 _Predazzo, ancient volcano of_, 165, fig. 67 Propylites, 199 Pseudo-dykes, 119 Pumice, how formed, 68 -- cause of white colour of, 71 -- floating on ocean, 73 -- on ocean-beds, 73 Pumice-cones, 154 _Puy de Pariou, Auvergne_, 193, 194, figs. 82, 83 Puzzolana, 89 RAIN, accompanying volcanic outbursts, 30 Rate of movement of lava-streams, 97 Rath, Professor Vom, 72 Red clay of ocean-beds, 74 Red Mountains, Skye, 144 Reservoirs beneath volcanoes, 145 Reyer, Dr. Ed., experiments of, 125, 160 Reykjanes, eruption of, in 1783, 102 Rhyolites, 50, 59 Richthofen, Von, cited, 196, 199, 200, 205 _Rocca-Monfina_, 178, fig. 77 -- --, 204 Rock-masses, movements of, 288 Rocky Mountains, 103 -- -- volcanoes of, 201 Rotomahana, sinter-terraces of, 185 _Ropy-lavas_, 98, fig. 24