About Earthquakes.

—Elastic fluids are, doubtlessly, the cause of the slight and perfectly harmless trembling of the earth’s surface, which has often continued for several days (as in 1816, at Scaccia, in Sicily, before the volcanic elevation of the island of Julia), as well as of the terrific explosions, accompanied by loud noise.

The focus of this destructive agent, the seat of the moving focus, lies far below the earth’s surface; but we know as little of the extent as we know of the chemical nature of these vapours that are so highly compressed.

At the edges of two craters, Vesuvius and the towering rock which projects beyond the great abyss of Pichincha, near Quito, I have felt periodic and very regular shocks of earthquakes, on each occasion from twenty to thirty seconds before the burning scoriæ or gases were erupted.

The great earthquake which destroyed the city of Lisbon on the 1st of November, 1755, was felt in the Alps, on the coast of Sweden, in the Antilles, Antigua, Barbadoes, and Martinique; in the Great Canadian Lakes, in Thuringia, in the flat country of Northern Germany, and in the small inland lakes on the shores of the Baltic.

A portion of the earth’s surface four times greater than that of Europe was simultaneously shaken.

As yet there is no manifestation of force known to us, including even the murderous inventions of our own race, by which a greater number of people has been killed in the short space of a few minutes; sixty thousand were destroyed in Sicily in 1693; from thirty to forty thousand in the earthquake of Riobamba, in 1797, and probably five times as many in Asia Minor and Syria, under Liberius and Justinian the elder, about the years 19 and 526.—Humboldt’s Cosmos.