BOOKS.
VESUVIUS.*
THE earlier portion of this exhaustive and interesting monograph is occupied with a detailed account of the growth and vicissitudes of the mountain Vesuvius, which is really a volcanic cone placed in the centre of an older and much larger crater, which forms a semicircular amphitheatre, and is known by the name of Somme. The history of Vesuvius is one of successive paroxysms of volcanic activity, alternating with longer or shorter intervals of more or less troubled repose. From its position in the centre of a fertile, populous, and classical region, we are in possession of a fuller and more authentic knowledge of this volcanic focus than of any other, and its annals extend backwards nearly to the birth of Christ. The first eruption upon record is the memorable outburst of A.D. 79, in which the elder Pliny lost his life, and the cities of Pompeii and Her culaneum were buried, the former by clouds of volcanic ashes, the latter by concreted mud. Of this celebrated outbreak we possess an extraordinarily graphic and striking account in the letters of Pliny the Younger, who was stationed at the time at Misenurn with his uncle. It is more than probable, however, that many periods of activity had preceded this in prehistoric times, and that Pompeii itself was built upon the lava-flows of an earlier eruption. For more than fifteen centtries the "horrible mountain" appears to have enjoyed a fitful repose, though several minor disturbances have been chronicled, and there were doubtless many others of which we possess no record. In December, A.D. 1631, there occurred a terrific convulsion, heralded by six months of earthquakes, accompanied by enormous ejections of vapour and ashes, charged with electric fires, and culminating in the emission of several streams of lava, some of which extended to a distance of five miles. In this awful paroxysm the entire summit of the mountain was blown off, and the towns of Torre del Greco, Resina, and Granatello were destroyed, with an estimated loss of 18,000 lives. During the next one hundred and fifty years Vesuvius was never really completely tranquil, but exhibited a long series of more or less violent eruptions, some of which were very considerable and caused great destruction. In 1794, however, took place one of the most terrible of all the known eruptions of Vesuvius, of which we extract the following account, taken by Professor Phillips from the narrative of Breislak, an Italian geologist :— " A violent earth-shock, felt at Naples, at 11 p.m., on the 12th of Juno, gave the signal of approaching disaster, and induced many persons to leave their homes for the night. Quiet returned till the evening of the 15th, when about 9 p.m. the symptoms of great agitation revived. At 20 p.m. violent earthquake shocks, and a sudden outburst of lava in the Pedementina, among the remains of earlier currents. Here a fissure was produced 2,375 feet long, and the lava issued from a space 237 feet in breadth. Tho lava which erupted threw up four cones, each crateriform (ono had a double crater); and from each arose showers of red-hot stones in such quick succession as to appear like one continuous sheet of fire in the air, with pulsations according to the variation of the expelling force. The showers really contained fluid or unsolidified lava which expanded in the air like soft paste. The lava, poured from fifteen mouths, was at first united in one stream, from which occasional flashes of light arose, produced by jets of hydrogen gas, which disengaged itself from the lava, as gases expand from the surface of an ordinary fluid. Running first towards Portici and Resina, the inhabitants of Torre del Greco, while sorrowing for the probable fate of their neighbours, gave joyful thanks in the churches for their own immunity. • Nescia mons hominum !' The lava divided, and three branches took their own wild ways. One ran 2,063 feet towards Santa Maria de Pugliano ; another flowed toward Resins. 3,181 feet ; and the remainder passed down the valley of .M.alomo, toward Torre del Greco. At the chapel of Bolzano, a branch parted to the south-east, and ran 1,490 feet; the main stream rushed on Torre, through several hollows, with a front of fire from 1,200 to 1,500 feet wide. Right down the main street toward the sea, and by several winding tracks amongst houses and churches, flowed the destructive lava ; reached the sea with a front of 1,127 feet broad and 15 feet high, and advanced into it 362 feet During this tremendous eruption at the base of the Vesuvian cone, and the fearful earthquakes which accompanied it, the summit was tranquil. The sky was serene, the stars brilliant, and only over Vesuvius hung a thick dark smoke cloud, lighted up into an auroral arch by the glare of a stream of fire more than two miles long, and more than a quarter of a mile broad. The sea was calm, and reflected the red glare ; while from the source of the lava came up continual jets of uprushing incandescent stones. Nearer to view, Torre del Greco in flames and clouds of black smoke, with falling houses, presented a dark and tragical foreground, heightened by the subterranean thunder of the mountain, and the groans and lamentations of fifteen thousand rained men, women, and children."
In the nineteenth century Vesuvius continued to give evidence of the mighty forces imprisoned beneath it, the exhibitions of 1822, 1834, 1855, and 1858 being the most important. In 1867 commenced the last eruption, and to this we are indebted for the valuable work before us, Professor Phillips having journeyed to Naples with the special intention of recording its phenomena. From the author's wide and well-deserved reputation, it is hardly necessary to say that his work is everything that could be desired; and it should be in the hands of all who either intend to visit Naples, or wish to have some knowledge of volcanos in general. The description of the scene of the eruption and of its adjuncts is extremely vivid, and is interspersed with numerous observations of high scientific value. The following picture of one of the more striking outbursts seems almost to transport us to the base of the fiery mountain :
"One more look at the evening lights of Vesm ins—the 27th of March—the grandest of all the exhibitions. What a spectacle ! One long burning stream down the whole of the north-western slope of the great cone, quite reaching into and spreadirg across the Ataio de Cavallo. On the top, fitful bursts of clouds of fiery botnbs and widespread ashes ; below just where it appeared last night, but now far brighter, and glowing with a full steady eye of light, the second great burst of light and motion. Now it spreads a bright cloud above ; then down to the valley knots and lines, sometimes double, of white or reddish fire, swelling into considerable masses, and broken into many gleaming points. Toward the base a wide cataract of fire is pouring toward us, and is stretching its red fingers over the older lava. Now and then a star-like point in advance seems to beckon onward,— 'Die froie Toehter der Natur :
Finally, in the deepest part of the visible horizon, a horizontal row of fourteen small bright star or gem-like fires marks the conquest of the current over the flat space of the Atrio, and seems to unite again the long separated masses of Somma and Vesuvius,—parent and child, the far-descended progeny of the struggling Titan."
Having given a full history of Vesuvius from the Plinian eruption of A.D. 79 up to the present day, Professor Phillips proceeds to consider the characteristic phenomena of eruptions, the periods of rest and activity, and the form and structure of the mountain. These chapters will be especially interesting to geologists, and though they do not contain much that is absolutely new, they are written with admirable clearness, and are not devoid of some remarkable deductions. One of the most noticeable of these is the apparent similarity or identity of the laws which regulate volcanic activity and the oceanic tides, as discovered by Professor Palmieri. This observer, namely, satisfied himself that the issues of lava had "a daily period of two maxima and two minima," the times of which underwent a daily retardation; whilst the cone of eruption threw up columns of ashes with more than average violence twice a day. It further appeared that the eruptions were "sensibly strengthened at the syzigies, and weakened at the quadratures, of the moon."
Chapter viii. gives us an excellent account of the neighbouring volcanic region of the Phlegrasan Fields, with striking descriptions of the Monte Nuovo, and the famous lake of Avernus, of which the latter is really an extinct and degraded crater. The last chapter of the work is naturally the most important, as it embodies the theoretical views to which the author has been conducted by a study of volcanic phenomena in general. We find it impossible to give any adequate account of the Professor's theory of volcanic excitement, but it will be eagerly read by all physicists, and cannot fail to be appreciated even by those who may not fully agree with the conclusions arrived at. As far as one important point is concerned, we are glad to see that the author has cast the weight of his distinguished authority in favour of the often
vilified view, that "beneath our feet, at a depth not too great to influence geological phenomena, the substance of the globe is
fluid with heat." The concluding passage is too striking to be omitted, and calls for no comment from us :—
" Here, then, we pause, not without a conviction that geology is acquiring, even with reference to the variable might of subterranean fire, a sure ground of conviction that it is part of a system of slow and measured change which has been traced in operation, through the members of the solar system and the starry spaces beyond, to the greater and more distant masses of shining vapour, which, though they stand to us, at present, as the 'flammantia mconia mundi,' may even now be silently gathering into new suns, and planets, and satellites ; or forming elliptic rings of asteroids, such as were seen on this morning of the 14th of November, 1868, by the author, at Oxford."
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