the remarkable iron-masses found at Ovifak in Greenland; and the indications which have been discovered of analogies between the composition and dynamics of our earth and those of other members of the family of worlds to which it belongs. While not evading the discussion of theoretical questions, I have endeavoured to keep such discussions in strict subordination to that presentation of the results attained by observation and experiment, which constitutes the principal object of the work. The woodcuts which illustrate the volume are in some cases prepared from photographs, and I am indebted to Mr. Cooper for the skill with which he has carried out my wishes concerning their reproduction. Others among the engravings are copies of sketches which I made.in Italy, Hungary, Bohemia, and other volcanic districts. The whole of the wood-blocks employed by Mr. Poulett Scrope in his work on Volcanoes were placed at my disposal before his death, and such of them as were useful for my purpose I have freely employed. To Captain S. P. Oliver, R.A., I am obliged for a beautiful drawing made in the Island of Bourbon, and to Mr. Norman Lockyer and his publishers, Messrs. Macmillan & Co., for the use of several wood-blocks illustrating sun-spots and solar prominences. J. W. J. LONDON: May 1881. ILLUSTRATIONS. Sections of igneous rocks illustrating the passage from the glassy to the crystalline structure. FIG. Frontispiece PAGE 1. Stromboli, viewed from the north-west, April 1874 to face p. 10 2. Map of the Island of Stromboli . 3. Section through the Island of Stromboli from north-west to south-east. 4. The crater of Stromboli as viewed from the side of the Sciarra during an eruption on the morning of April 24, 1874. 11 13 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 7. Minute cavities, containing liquids, in the crystals of rocks. (After Zirkel). 43 to face p. 60 8. Minute liquid-cavity in a crystal, with a moving bubble. (After Hartley) 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) 62 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 FIG. 12. Outlines of the summit of Vesuvius during the eruption of 1767. (After Sir W. Hamilton) 13. Crater of Vesuvius formed during the eruption of 1822 (After Scrope). PAGE to face p. 80 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) 16. Summit of Vesuvius in 1843 86 கசு 85 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.) 19. Lava-stream (obsidian) in the Island of Vulcano, showing the imperfect liquidity of the mass 20. Interior of a rhyolitic lava-stream in the Island of Lipari, showing broad, sigmoidal folds, produced by the slow movements of the mass 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 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. 98 24. Concentric folds on mass of cooled lava. (After Heaphy). 100 25. Mass of cooled lava formed over a spiracle on the slopes 26. Group of small cones thrown up on the Vesuvian lava-current of 1855. (After Schmidt) 27. Natural section of a lava-stream in the Island of Vulcano, showing the compact central portion and the scoriaceous upper and under surfaces 100 101 28. Section of a lava-stream exposed on the side of the river Ardèche, in the south-west of France. (After Scrope). 106 |