MAN AND VOLCANOES.
MAN is justly proud of his command over inanimate Nature. Since he learnt the use of tools—and so established, a great gulf between himself and all other animals—he has achieved wonderful things. He can make a desert blossom like the rose, can turn foaming rapids into navigable rivers, and can harness sounding cataracts to turn his engines and light his cities. But there are still a few natural phenomena which fill him with a wholesome sense of powerlessness. The eruption of Vesuvius which took place last week-end is a striking example. All the resources of science fail to minimise the destruction which is produced by an outbreak of the nether fires. The King of Italy in his motor-car is as help- less as Canute. We read of the feeble efforts of the Italian troops to erect barricades against the streams of lava— flowing without haste, but also without rest—and so to save the priceless treasures of Pompeii, which were at one time threatened by this eruption, but now happily seem to have been preserved by the stoppage of the lava in time. Pompeii, of course, was destroyed originally by a shower of volcanic ashes, and the contour of the mountain is such that the lava, following the stream-lines, is not likely to reach the city which has been recovered from its agelong burial by the labour of several generations. The fresh destruction of this invaluable record of Roman manners would be a loss that the world would feel keenly, and. there will be general rejoicing at its preservation. In some ways, the history of the great eruption which restored Vesuvius to activity in A.D. 79, after a sleep which dated back to prehistoric times, has been curiously repeated in this case. As we read. of an Italian squadron being ordered to Naples to afford such assistance as its "handy men" can suggest we are reminded of the Roman fleet of which the elder Pliny was in command when he headed that historic landing-party which approached so near the scene of destruction that its fat and short-winded commander fell a victim to his scientific enthusiasm. Men of science in all ages have cheerfully hazarded their lives for the sake of widening knowledge, and Pliny's ill-fated zeal finds a parallel in the quiet heroism of Professor Matteucci, the Director of the Vesuvius Observatory, who has stuck to his •post on the slopes of the volcano in the midst of darkness and terror. Whilst the mountain was shaking under him with a violence which "displaced the seismic apparatus," as he coolly says, and the windows of the Observatory were being battered in by bombs projected from the crater, he kept a careful record of the successive phenomena, which he telegraphed to Rome for the benefit of science. Fortunately, this courageous observer seems to have come safely through an ordeal which cannot have been surpassed in terror or danger by any of the achieve- ments recorded in the annals of the Victoria Cross. It is deeds of this kind which show that man, after all, rises superior to even those natural cataclysms which he is powerless to check : a reed, says Pascal, but a reed which thinks.
In spite of the serious loss of life and the destruction of several villages on the slopes of -Vesuvius, this eruption has been by no means so costly as that of 79, which destroyed two flourishing cities, or that of 1631, in which more than eighteen thousand persons are said to have lost their lives. Nor can it compare in violence with the eruption of Krakatoa in 1883, or that of the Japanese Bandaisan in 1888, or of Mont Pelee in 1902. It has created so much interest because it is comparatively near to us. Every travelled Englishman knows the beautiful Bay of Naples, and most of us have seen the huge cone of Vesuvius, crowned with its perennial feather of smoke, even if we have not taken advantage of Messrs. Cook's convenient funicular railway to approach the very lip of the crater and burn our boot-soles on its heated edge. There is some truth in Macaulay's remark that a broken head in Coldbath Fields is more interesting than a pitched battle in India, and it is human to be specially thrilled by cataclysms that affect districts with which we are familiar. Hence comes the interest that we take in reading of "the great sinful streets of Naples" ankle-deep in volcanic mud, and veiled from the noonday sun by an impenetrable cloud of dust. We may even expect to see a speedy evidence of the eruption in the haze which will reach our own skies before long, and produce more of those weird. and beautiful sunsets which were familiar when Krakatoa and Mont Pelee filled the upper air with their intangible dust. We naturally ask the geologists, with an agreeable thrill, -whether they are certain that we are free from all likelihood of a similar outbreak in our own islands. The answer is not quite so reassuring as we could wish. Our islands are covered with the relics of prehistoric volcanic activity. The hills of the Lake District—Snowdon and its mountain fellows—the great basalt plateaux of Antrim and Skye—the conical Laws of North Berwick and Largo, with Arthur's Seat and the Castle Rock of Edinburgh—are all the product of ancient volcanoes. There is no real guarantee that the central fires may not burst out again at any of these spots, except the fact that they have been quiescent for a thousand centuries or more. We are all living on the surface of a great boiler charged with high-pressure steam, of which Vesuvius and Hekla and Mauna, Loa are so many safety-valves. The true nature of volcanic activity is understood in principle, though many of its details are still obscure. The earth possesses an intensely heated interior, in which the heat and pressure combine to keep all substances in the state of true gases, although these same gases must be denser and more rigid than steel. Between this singular interior and the solid crust on which we live there must be a layer of molten magma, or lava, which furnishes the materials and the energy for volcanic activity. It is permanently under great hydrostatic pressure from the weight of the superincumbent rocks, and any weakening in the crust serves as an opening for this molten magma to force its way up to the surface. We do not as yet thoroughly understand the laws of such weakenings; but we do know that certain regions are subject to their occurrence, and that others are not ; and within historic times our own islands have fortunately fallen within the latter category. In discussing the recent eruption of Vesuvius, an ingenious friend suggested to the writer to consider whether a multi-millionaire, greedy for a new excitement, could possibly devote the great resource of his wealth to produce a volcano in some remote part of the British Islands. In theory the thing is not impossible. We know that the raw material of volcanic energy lies every- where at a depth of a few miles below the surface, and that if it could once be tapped and set going it would probably take the work over, and build a very respectable volcano,— say over that great fault in Perthshire which is still the main focus of British earthquakes. One of the chief agents in volcanic eruptions is the explosive force of steam. Attempts have been made to discover some relation between meteorological changes and eruptions, and it has been established that these events are more frequent after a rainy season. Water percolating through the crust, and sinking to the heated depths at which it is raised above its critical temperature—about 773° Fahr.—becomes an exceedingly powerful explosive, as soon as an outlet for its powers is discovered. It is this superheated water, rising in the volcanic vent, which flashes into steam and. disrupts the lava into that fine dust which has been cover- ing the streets in Naples, and which once buried Pompeii. If a shaft could be dug sufficiently deep to reach the sub- terranean fires, and a river turned into it, we should have all the conditions necessary to start a very fine volcano anywhere in the British Isles. Fortunately, no device has yet been invented for tunnelling to the necessary depth,— though something might be done by boring down a mile or so and then exploding fifty tons of dynamite, and repeating the process until Nature took it over. Still more fortunately, such an amusement is not likely to suggest itself to even a multi-millionaire, though a modern Nero might see in it a chance of improving upon the Emperor who burnt Rome. We are perhaps more likely to return to the mediaeval view that the earth is a living creature, and that volcanoes and earthquakes are her way of scratching off her human fleas when they irritate her beyond endurance.
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