Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/448

Rh and embracing by its fringe Candia, and the whole southern coast of Asia Minor, extends over Cyprus, and joins into the great Syrian earthquake region. The same principle guides this linear distribution throughout; it follows, with variable intensity, the great lines of elevation.

Returning, however, nearer to our own district. Each focal centre, moves in time along the locus line, so that its greatest energy is not recurrent at the very same spot, or not until after a long period. In the last century, the centre of seismic intensity, for that part of the band to which our earthquake belongs, was situated midway between the Gulfs of St. Euphemia and Squillace, in Calabria: it has continued since to move to the northward, and its present centre, is somewhere between the Melfi focus, and that of the earthquake of December, 1857, in fact, somewhere beneath, or north or south of, the great mountain knot of Muro and Bella, (see Maps A and B,) where the north and south, and the east and west Apennine ridges, cross each other.

This slow secular movement of the centre of temporary intensity, along the line of locus, has been noticed by most of the Italian authors, (Grimaldi, Battista, and others,) who have treated of the earthquakes of the south of the peninsula. During the same interval, to the westward of the Straits of Messina, the centre of temporary intensity, appears to have been moving westward, and seems to be at present nearer to the Palermo end of the island, than to Messina.

These facts distinctly point towards some great conclusions. They indicate that the same forces, whatever they may be, that develop themselves, as volcanic vents, and as earthquakes, are operative everywhere along the lines