MACCULLOCH, cited, 207, 208 _Madeira, cliff-section in_, 128, fig. 47 Magmas, theory of, 201 -- objections to, 202, 203 Mallet, Mr., cited, 269, 343, 346 _Mamelons of Bourbon_, 126, 127, figs. 45, 46 Maskelyne, Professor, cited, 314 Massa di Somma, destruction of, 26 Mauna Loa, 138 Metamorphism around volcanic vents, 145 Meteorites, nature of, 312 -- composition of, 313 -- minerals of, 314 -- classification of, 315 Melaphyres, 262 Miascite, 59 Michel Lévy, M., 110 Micro-crystalline base, 58 Microliths. _See_ Crystallites Microscopic study of lavas, 50 Minerals in lavas, 51 -- of Vesuvius, 46 Mineral-veins, formation of, 149 -- connection with volcanoes, 220 -- nature of materials in, 321 _Misenum, Cape of, section of tuff-cone of_, 121, fig. 38 Modena, mud-volcanoes of, 182 _Mont Dore, section at_, 130, fig. 48 Monte Cerboli, Tuscany, 216 Monte Massi, Tuscany, well at, 341 Monte Nuovo, history of formation of, 76 -- -- _description of_, 77, 78, fig. 10 -- -- 152 -- -- crater of, 168 -- -- production of fissure at, 190 Monte Rotondo, Tuscany, 216 Moon, effect of internal forces on, 305 Mountains, all volcanoes not, 2 Mountain-chains, formation of, 291 -- -- all of recent date, 292 Mud-streams at volcanoes, 30 Mud-volcanoes, formation of, 181, 182 _Mull, dissected volcano of_, 142-4, figs. 57, 58 Muscovite, absence of, from modern lavas, 268 NEBULAR hypothesis of Laplace, 325, 352 -- -- of Kant, 352 New Zealand, geysers of, 217 -- -- volcanoes of, 135 -- -- volcanic cones in, 79 Niedermendig, lava of, 103 Nordenskiöld, Professor, cited, 318 OBSERVATORY on Vesuvius, 24, 37 -- on Etna, 37 Obsidian, 59 Oceans, depth of, in volcanic areas, 242 Oceanic islands, volcanoes in, 228 Oliver, Capt. S. P., 92 Oldhamite, 314 _Outlines of Vesuvius_, 87, fig. 17 Ovifak, iron-masses of, 319 Oxidation of materials of globe, 324 Oxygen, proportion in lavas, 47