CADER IDRIS, 274 'Calderas,' formation of, 180 Caldera of Palma, 209 Cambro-Silurian volcanoes of British Islands, 274 _Campi-Phlegræi, map of_, fig. 11 -- -- volcanoes of, 79 -- -- tuff-cones of, 118 -- -- fissures in, 197 Carbonic acid in cavities of crystals, 63 Carboniferous volcanoes of British Islands, 275 Carlsbad, Strudel of, 218 -- Strudelstein of, 184 Caspian Sea, mud-volcanoes of, 182 Catacecaumene, volcano cones in, 79 Cause of proximity of volcanoes to sea, 239 Central Asia, volcanoes of, 236 -- America, mud-volcanoes, 182 -- Pacific, volcanoes of, 236 'Challenger,' H.M.S., voyage of, 73 -- -- soundings of, 359 Chance, Messrs., of Birmingham, 55 Charnwood Forest, ancient volcanic rocks of, 259 Chemical deposits at Vulcano, 44 -- -- on surfaces of lavas, 110 -- elements present in lavas, 46 -- theory of volcanoes, 344, 346 Chiaja di Luna, 108 Chimborazo, size of, 44 -- 151 Chodi-Berg, Hungary, 161 _Citlaltepetl, view of_, 169, fig. 69 Coast-lines, proximity of volcanoes to, 228 Cole, Mr. Grenville, 110 Colours of lavas, 49 Columns in lava, 105 -- -- dimensions of, 105 -- radiating in intrusive masses, 136 Columnar structure in lavas, 104 -- -- origin of, 105 _Columnar lava-stream on the Ardèche_, 107, fig. 28 Combustion, does not take place at volcanoes, 2 Composite cones, 128, 161 Comstock mines, temperature of, 342 _Concentric jointing in lava_, 108, fig. 30 _Cones composed of viscid lava_, 129, fig. 43 -- miniature on lava-streams, 100, 101, figs. 25, 26 -- natural sections of, 129 -- shifting of axis in, 167 Coolin Hills, Skye, 144 Cotopaxi, volcanic dust of, 69 -- _view of_, 168, fig. 68 Craters, formation of, 82 -- origin of, 167 -- position of, 167 -- fissuring of sides, 180 Crater of Stromboli, aperture at bottom of, 15 Crater-lakes, formation of, 171 -- of Agnano, 171 -- of Albano, 171 -- of Avernus, 171 -- _of Bagno_, 171, fig. 71 -- of Bolsena, 171 -- of Bracciano, 171 -- of Frascati, 173, 175 -- _of Gustavila_, 171, fig. 72 -- of Laach, 171 -- of Nemi, 171 Crater-rings, formation of, 170 _Crater-ring of Somma_, 177, fig. 76 Crater-ring of Pianura, 174 -- -- of Piano di Quarto, 174 -- -- of Vallariccia, 174 Creuzot, shafts at, 340 'Critical point' of liquids, 63 Crust of globe, definition of, 308 Crystals in lavas, 51 -- -- formed of crystallites, 54-57 -- -- formed in subterranean reservoirs, 60 -- -- interruption in growth of, 60 -- pressure under which formed, 65 -- deposited on surface of lava, 110 -- porphyritic, origin of, 256 Crystalline minerals formed beneath volcanoes, 146, 147 -- -- ejected from volcanoes, 147 Crystallised minerals of volcanoes, 46 Crystallites, aggregates of, 54, _Frontispiece_ Crystallites in lavas, 53, _Frontispiece_ Crypto-crystalline base, 57 'Cupolas,' 135 Corral of Madeira, 209