| Sections of igneous rocks illustrating the passage from the glassy to the crystalline structure | Frontispiece | |
| Fig. | Page | |
| 1. | Stromboli, viewed from the north-west, April 1874 | to 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-stream | to 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 Hebrides | to 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 cones | to 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 rocks | to 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 |