DACITES, 198 Dana, Professor, J. D., cited, 100, 159, 291, 301, 327, 338, 339 Darwin, Mr., cited, 245, 246, 271, 289 Daubeny, cited, 182 Daubrée, M., cited, 147, 315, 320, 358 Daubréelite, 314 Davy, Sir Humphry, chemical theory of volcanoes, 344, 345 Deccan of India, 103 Density of the earth, 306 _Denuded cones and craters_, 158, fig. 59 Denudation, effects of, on volcanoes, 114 Deposits about volcanic fissures, 42 Detonations at Vesuvius, 26 Devonian volcanoes of British Islands, 274 Diorite, 59 Dolomieu, cited, 4, 39 Durocher, cited, 201 Dykes, formation of, 116, 117, 209, 210 -- structure of rock in, 211 -- pseudo-, 119 Dynamical theory of volcanoes, 347, 348 EARTH'S interior, nature of, 309 -- -- physical condition of, 325 -- -- hypothesis concerning, 328-330 -- relation to other planets, 310, 311 Earthquakes, depth of origin of, 343, 344 -- connection with volcanoes, 343 -- accompanying Vesuvian eruption of 1872, 27 Ebullition, compared to volcanic eruptions, 19, 20 Eifel, volcanic cones of, 45 Ejected blocks, 45 -- materials, height to which thrown, 72 -- -- stratification of, 117-119 Elements, pyroxenic and trachytic, theory of, 201 Elevation-craters, theory of, 135, 200 Erroneous opinions, sources of, in regard to volcanoes, 2 Eruptions, feeble and violent compared, 31 -- prediction of, not possible, 32 -- intervals between, 33 -- of varying intensity, 33 -- and barometric pressure, 36 -- effects of repetition of from same fissure, 80 Eruptive action in sun and moon, 360-369 Etna, ideas of ancients concerning, 3 -- and Anne Boleyn, 3 -- observatory on, 37 -- size of, 44 --, 151 -- eruptions at summit and on flanks, 207 _Etna, dyke and lava-stream in_, 133, fig. 54 _Etna, views of_, 162, 163, figs. 62, 63 Euganean Hills, 139 -- -- volcanoes of, 201 Europe, volcanoes of, 227 Extra-terrestrial rocks, 316 _Extra-terrestrial rocks, relation to ultra-basic rocks_, 322, fig. 88 FELSTONES, 263 Ferric-chloride, mistaken for sulphur, 41 _Fissure on flanks of Etna_, 194, fig. 84 Fissure-eruptions, 188 Fissures, volcanic cones on, 194 -- systems of, 198 Fingal's Cave, 106 Flames, phenomena mistaken for, 2 -- at volcanoes, feebly luminous, 17 -- false appearance of, in volcanoes, 17 Flames at volcanic vents, 41 Flashing lighthouse, compared to Stromboli, 10 Floods, accompanying volcanic outbursts, 30 Forbes, Mr. David, cited, 337, 339 Fossils, from beneath Vesuvius, 45 -- supposed in basalt, 250 Fouqué, M., cited, 110, 213 Fumaroles, gases emitted from, 213 Fusiyama, form of, 90, 166 _Fusiyama_, 178, fig. 77