LAACHER SEE, minerals ejected at, 149 _Lac Paven, Auvergne_, 171, fig. 70 'Laccolites,' formation of, 208 Lago di Bolsena, 173, 175 Lago di Bracciano, dimensions of, 172, 173 Lake Avernus, 215 Lapilli, 70 Laplace, nebular hypothesis of, 325, 352 Lavas, action of acid gases on, 41 -- resemblance to slags, 46 -- chemical elements in, 46 -- oxygen in, 47 -- silicon in, 47 -- proportion of silica and other oxides in, 47 -- silicates in, 47 -- acid, intermediate, basic, 48 -- specific gravities of, 49 -- colours of, 49 -- microscopic study of, 50 -- fusibility of, 51 -- minerals in, 51 -- artificially fused, 51 -- crystals in, 51, 93 -- ground mass of, 52 -- crystalline forms of, 59 -- of Bohemia, 103 -- of Hungary, 96, 103 -- of Kilauea, 95 -- of Lipari, 96 -- of Niedermendig, 103 -- of Vesuvius, 104 -- of Volvic, 95 -- of Volcano, 95 -- presence of water In, 102 -- chemical deposits on, 110 -- different fluidity of, 204 -- augite and hornblende in, 267 _Lava, cascade of_, 93, fig. 18 Lava-cones, composed of liquid lava, 125 -- -- of viscid lava, 126, 127 -- characters of, of liquid lava, 159 -- -- of viscid lava, 160 _Lava-cones, outlines of_, 160, fig. 60 Lava, in deep-seated reservoirs, 138 -- consolidation of, at great depths, 139 Lava-fountains, 94 _Lava-sheets, intrusive_, 136, 137, fig. 56 'Lava' ornaments of Naples, 45 'Lava,' slow-cooling of, 110 -- a bad conductor of heat, 110 -- ice under, 110 Lava-streams, nature of movements, 92 -- difference in liquidity of, 92 -- miniature cones on, 100, 101 -- vast dimensions of, 102 -- structure of, 103 -- position of columns in, 106 -- sinking of surface of, 111 'Lave di fango,' 30 'Lave di fuoco,' 30 Lawrencite, 314 Laws of volcanic action, 38 Le Conte, cited, 347 Leucite, absence from ancient lavas, 268 Lightning, accompanying volcanic outbursts, 28 Linear arrangement of volcanic vents, 191 -- -- of volcanoes, 231 Lipari Islands, 3, 39 -- -- fissures in, 197 -- -- pumice-cones in, 154 -- -- order of appearance of lavas in, 200 -- -- _breached pumice-cones in_, 124, fig. 41 -- -- _map of_, 192, fig. 81 -- -- _lavas of_, 96, figs. 20, 21 Liquids in cavities of crystals, 63 _Liquid cavities in lavas_, 60, fig. 7 -- -- _spontaneous movement of bubbles in_, 62, fig. 8 -- -- spontaneous movement of bubbles in, cause of, 65 Lockyer, Mr. Norman, cited, 322, 363, 364 _Lunar craters_, 368, fig. 95 Lyell, Sir Charles, cited, 135, 167, 197