Earthquakes

The Popular Science MontMy for Octobor lias an interesting and instructive paper on the phenomena of earthauakes, and the caufleB that produce ïem, from the pen of Prof. John J. Lake. The origin of eartliquakes, says Mr. Lake, has been ansigned to many causea, as the fnlliüg in of caverna, steïiru, the combustión of gases, volcanic and electric action. Great subterranenn noises and reporta resembling thunder constitute the first features to m notieed concerniug earthquakes. Father Kircher describes them aa " a horrid sound reseinbling that oí au infinito number of chariote driven fiercely forward, the wheels rattling, and the thongs of the whips cracking." At Colares, noar Lisbon, ín ] 755 the sound of an earlhquake is said to have been like " that of chariots, which increased till it oqualed the roar of caunon." At Lisbon it resembled "a rattling of coaches in the street, with a frightful noise luidergi-ound, resembling the rumbling of distant thunder." Various earthquakes have been Raid to resemble in sound empty cari'iages and the rolling of heavy vehicles. A second feature of these phenomena is tho upheaviug of the ground during their prevalence, which is one causo of the sea retiring. During the great earthquake at Lisbon the bar at the mouth of the Tagus was laid bare. Other results of the upward moveinent were observed elsewhere. The water in a pond at Dunfital, in Suffolk, was jerked into the foi-m of a pyramid. At some places the water was tossed out of the wells. At Loch Lomond, in Scotland, a krge stone waa forced out of the water, and at Riobamba, South America, on the 6th of January, 1797, the bodiesof many of the inhabitants were thrown by this vertical action upon the hill of La Cullca, which is sev'. eral hundred feet high on the oppoeite ! side of the rirer. A third peculiarity ia the frequent horizontal and circular motion of the soil walls that had served to divide fields have been completely changed in direction, but without having been shattered or overthrown. Houses have also exchanged situations with each other. It has been observed that cloucis have become fixed or suspended over particular spots affocted, or about to be affected, by earthquake, as in London in 1149. Explosiona of great violence frequently attend these convulsions, often with disastrous resulta. iWhen Millitello was destroyed there wasa great explosión heard in the fog that euveloped it. A similar explosión was heard in 1783, at Castel Nuovo, in Calabria, when that place was overwhelmed. A further peculiarity is the exemption of eertain spots, although the shocks were feit at all tho surrounding neighborhood. Thus at Manchester, in 1777, St. Paul's Church and the Dissenting Chapel escaped. Earthquakes are very frequently atteuded by thunder and lightning. At Munster, 'in 1612, thunder and lightning were heavy during an earthquake; and in Sicily, in 1693, it caused very great mischief. This conjunction of lightning with earthquake was notieed by Luke Howard, and constitutes what he designates "spurious earthquake." Peculiar rushing noises have also at times been perceived. These convulsions are attended by the disturbance of the niagnetic needie, and oompasses on board ship are for a long time'useless. The theory of the falling in of cavems being the causo of these phenomena cannot be maintained,and the hypothesis that they are caused by steatn or the explosión of confined gases has scarcely a better foundation. The volcanic and ignepus theory is not soeasiiy to be disposedof, for it appears very 'clear that volcanic eruptions do produce earthquakes. Volcanoes produce these disturbantes in two ways : 1. By their own direct motion. 2. By disturbing the electric equilibrium in their neighborhood. By far the most prominent agent seems to be electricity, and the Italiana, who suffer so much from these calamitieg, consider it to be the only cause. On the lOth of January the castle of Augusta was blown up by the lightning flring the powder-magazine. At Mineo, on the llth, the shock was attended by " a mighty storm of lightning, ihunder and hail that lasted six hours." The Archbishop's palace at Montreal was set on flre by the lightning. JEtna enaitted great noises, flamea and ashes during the shocks that overthrew Catania, j but there does not appear to have been eruption. Furia, situated among stone quarries, disappeared, and at several parts of the hill the rocks, which were Í previously almost as white as Geneva marble, had changed, and in the clefts made by the earthquake had become of a burnt color, as if flre and powder had been employed to rend them asunder. MUlitello seems to have been destroyed before the llth of January, for the country people, who dwelt on the neighboring ridge of mountains, affii-med that it waa not to be íeen on thd morning of that day, to which time, from 12 o'clock on the' 8th, it had been concealed in a thick fog. During the interval the mountain that lay on the north side of town had been spilt asunder - one portion overwhelming Millitello, so that not au inhabitant escaped. Francofonte, built ehiefly of wood, eecaped with little damago from the shocks, but was fired by lightning; the spire of the church - wood covered with lead - burnt down, and the nunnery of the Carmelites entirely destroyed so suddenly that five of the nuns were stifled in their beds. The Jargest part of the inhabitants of Luochela escaped by flying from the town on the sudden disappearance of the oastle, sitnated on rising groimd. Kagusa experienoed shocks on the 8tli, with violent thunder and lightning. At Specufurno, on tlie lüth, "from morning till night there was never heard so violent a storm of thunder ajid lightning, as if heaven and earth had been mixing together;" the townhouse and several other honses were destroyed by it. The peasants on the neighboring hills obsorved that thia lightning had bnrnt the vines so that no ! erop could be expected f or the Feason.