ILLUSTRATIONS.

Sections of igneous rocks illustrating the passage from the glassy to the crystalline structureFrontispiece
Fig.Page
1.Stromboli, viewed from the north-west, April 1874to face p. [10]
2.Map of the Island of Stromboli[11]
3.Section through the Island of Stromboli from north-west to south-east[13]
4.The crater of Stromboli as viewed from the side of the Sciarra during an eruption on the morning of April 24, 1874.[14]
5.Vesuvius in eruption, as seen from Naples, April 26, 1872. (From a photograph)to face p. [24]
6.View of Vulcano, with Vulcanello in the foreground—taken from the south end of the Island of Lipari[43]
7.Minute cavities, containing liquids, in the crystals of rocks. (After Zirkel)to face p. [60]
8.Minute liquid-cavity in a crystal, with a moving bubble. (After Hartley)[63]
9.Cavity in crystal, containing carbonic-acid gas at a temperature of 86° F., and passing from the liquid to the gaseous condition. (After Hartley)[64]
10.Monte Nuovo (440 ft high) on the shores of the Bay of Naples. (After Scrope)[76]
11.Map of the district around Naples, showing Monte Nuovo and the surrounding volcanoes of older date[78]
12.Outlines of the summit of Vesuvius during the eruption of 1767. (After Sir W. Hamilton) to face p. [80]
13.Crater of Vesuvius formed during the eruption of 1822 (After Scrope)[82]
14.Crater of Vesuvius in 1756, from a drawing made on the spot. (After Sir W. Hamilton)[84]
15.The summit of Vesuvius in 1767, from an original drawing. (After Sir W, Hamilton)[85]
16.Summit of Vesuvius in 1843[86]
17.Outlines of Vesuvius, showing its form at different periods of its history[87]
18.Cascade of lava tumbling over a cliff in the Island of Bourbon. (After Capt. S. P. Oliver, R.A.)[93]
19.Lava-stream (obsidian) in the Island of Vulcano, showing the imperfect liquidity of the mass[95]
20.Interior of a rhyolitic lava-stream in the Island of Lipari, showing broad, sigmoidal folds, produced by the slow movements of the mass[96]
21.Interior of a rhyolitic lava-stream in the Island of Lipari, showing the complicated crumplings and puckerings, produced by the slow movements of the mass[96]
22.Vesuvian lava-stream of 1858, exhibiting the peculiar 'ropy' surfaces of slowly-moving currents. (From a photograph)to face p. [98]
23.Vesuvian lava-stream of 1872, exhibiting the rough cindery surfaces characteristic of rapidly flowing currents. (From a photograph)to face p. [96]
24.Concentric folds on mass of cooled lava. (After Heaphy)[100]
25.Mass of cooled lava formed over a spiracle on the slopes of Hawaii. (After Dana)[100]
26.Group of small cones thrown up on the Vesuvian lava-current of 1855. (After Schmidt)[101]
27.Natural section of a lava-stream in the Island of Vulcano, showing the compact central portion and the scoriaceous upper and under surfaces[104]
28.Section of a lava-stream exposed on the side of the river Ardèche, in the south-west of France. (After Scrope)[106]
29.Portion of a basaltic column from the Giant's Causeway, exhibiting both the ball-and-socket and the tenon-and-mortise structure [107]
30.Vein of green pitchstone at Chiaja di Luna, in the Island of Ponza, breaking up into regular columns and into spherical masses with a concentric series of joints. (After Scrope)[108]
31.Illustration of the 'perlitic structure' in glassy rocks[109]
32.Transverse section of a lava-stream[111]
33.The Kammerbühl, or Kammerberg, Bohemia (as seen from the south-west)[113]
34.Section of the Kammerbühl in Bohemia[114]
35.Natural section of a volcanic cone in the Island of Vulcano[116]
36.Section in the side of the Kammerbühl, Bohemia[118]
37.Experimental illustration of the mode of formation of volcanic cones, composed of fragmental materials[120]
38.Natural section of a tuff-cone, forming the Cape of Misenum, and exhibiting the peculiar internal arrangement, characteristic of volcanoes composed of fragmentary materials. (After Scrope)[121]
39.Section of a small scoria-cone formed within the crater of Vesuvius in the year 1835, illustrating the filling up of the central vent of the cone by subsequent ejections. (After Abich)[122]
40.Volcanic cones composed of scoriæ, and breached on one side by the outflow of lava-currents. (After Scrope)[128]
41.Campo Bianco, in the Island of Lipari. A pumice-cone breached by the outflow of an obsidian lava-streamto face p. [124]
42.Volcanic cones in Auvergne, which have suffered to some extent from atmospheric denudation. (After Scrope)[124]
43.Experimental illustration of the mode of formation of volcanic cones composed of viscid lavas. (After Reyer)[126]
44.The Grand Puy of Sarcoui, composed of trachyte, rising between two breached scoria-cones (Auvergne). (After Scrope)[126]
45.Volcanic cone (Mamelon) composed of very viscid lava (Island of Bourbon). (After Bory de St. Vincent) [127]
46.Another Mamelon in the Island of Bourbon, with a crater at its summit. (After Bory de St. Vincent)[127]
47.Cliff-section in the Island of Madeira, showing how a composite volcano is built up of lava-streams, beds of scoriæ, and dykes. (After Lyell)[125]
48.Section seen at the cascade, Bains du Mont Dore. (After Scrope)[130]
49.Section in the Island of Ventotienne, showing a great stream of andesitic lava overlying stratified tuffs. (After Scrope)[130]
50.Cliff on the south side of the Island of San Stephano[131]
51.The headland of Monte della Guardia, in the Island of Ponza[131]
52.Western side of the same headland, as seen from the north side of Luna Bay[132]
53.Sea-cliff at Il Capo, the north-east point of Salina, showing stratified agglomerates traversed by numerous dykes, the whole being unconformably overlaid by stratified, aqueous deposits[137]
54.Section observed in the Val del Bove, Etna, showing a basaltic dyke, from the upper part of which a lava-current has flowed[138]
55.Basaltic dykes projecting from masses of stratified scoriæ in the sides of the Val del Bove, Etna[134]
56.Sheets of igneous rock (basalt) intruded between beds of sandstone, clay, and limestone (Island of Skye)[137]
57.Plan of the dissected volcano of Mull in the Inner Hebridesto face p. [142]
58.Section of the volcano of Mull along the line A B " [142]
59.Summit of the volcano of Monte Sant' Angelo, in Lipari, exhibiting a crater with walls worn down by denudation[158]
60.Outlines of lava-cones[160]
61.Diagram illustrating the formation of parasitic cones along lines of fissure formed on the flanks of a great volcanic mountain[162]
62.Outline of Etna, as seen from Catania [162]
63.Outline of Etna, as seen from the Val del Bronte[163]
64.Plan of the volcano forming the Island of Ischia[163]
65.A primary parasitic cone, with a secondary one at its base—Ischia[164]
66.Scoria-cone near Auckland, New Zealand, with a lava-current flowing from it. (After Heaphy)[165]
67.Section of rocks below the ancient triassic volcano of Predazzo in the Tyrol[165]
68.Cotopaxi, as seen from a distance of ninety miles. (After Humboldt)[168]
69.Citlaltepetl, or the Pic d'Orizaba, in Mexico, as seen from the Forest of Xalapa. (After Humboldt)[169]
70.Lac Paven, in the Auvergne. (After Scrope)[171]
71.The crater-lake called Lago del Bagno, in Ischia, converted into a harbour[172]
72.Lake of Gustavila, in Mexico. (After Humboldt)[172]
73.Peak of Teneriffe, surrounded by great crater-rings. (After Piazzi-Smyth)[175]
74.The volcano of Bourbon, rising in the midst of a crater-ring four miles in diameter. (After Bory de St. Vincent)[176]
75.The volcano of Bourbon, as seen from another point of view, with three concentric crater-rings encircling its base. (After Bory de St. Vincent)[176]
76.Vesuvius as seen from Sorrento, half encircled by the crater-ring of Somma[177]
77.Outlines of various volcanoes illustrating the different relations of the craters to conesto face p. [178]
78.Island thrown up In the Mediterranean Sea in July and August, 1831. (After the Prince de Joinville)[179]
79.Sinter-cones surrounding the orifices of geysers[183]
80.Diagram illustrating the mode of formation of travertine- and sinter-terraces on the sides of a hill of tuff[185]
81.Map of the volcanic group of the Lipari Islands, illustrating the position of the lines of fissure upon which the volcanoes have been built up [192]
82.The Puy de Pariou, in the Auvergne, illustrating the shifting of eruption along a line of fissures[193]
83.Ideal section of the Puy de Pariou[194]
84.Fissure formed on the flanks of Etna during the emotion of 1865. (After Silvestri)[194]
85.Plan of the Island of Vulcano, based on the map of the Italian Government[196]
86.Vulcanello, with its three craters[197]
87.Section of basalt from Ovifak, Greenland, with particles of metallic iron diffused through its mass[319]
88.Diagram illustrating the relations between the terrestrial and the extra-terrestrial rocksto face p. [322]
89.A group of sun-spots. (After Secchi)[362]
90.A sun-spot, showing the great masses of incandescent vapour rising or falling within it. (After Secchi)[363]
91.The edge of a sun-spot, showing a portion of the prominent masses of incandescent gas (A) which detached itself at B and floated into the midst of the cavity. (After Norman Lockyer)[363]
92.Drawing of a solar prominence made by Mr. Norman Lockyer, March 14, 1869, at 11 h. 5 m. A.M.[364]
93.The same object, as seen at 11 h. 15 m. on the same day. (After Norman Lockyer)[365]
94.Drawings of a solar prominence at four different periods on September 7, 1871. (After Young)[366]
95.A group of Lunar craters (Maurolycus, Barocius, &c.), the largest being more than sixty miles in diameter[368]