the oscillation of the eminence, and the vibration of the wave, conspire to its overthrow.
If it stand upon an eminence or table, of loose material, with steep scarps, its fate will be the same, with the added evil, of masses of the loose material being thrown and shed down as at Montemurro along with the ruin of the place.
Two towns may be closely adjacent, the one on a lofty hill, the other low lying in the plain, at its foot, and either may be on the rock, or on the clays; and yet, without a knowledge of what country intervenes, between them and the focal centre, it shall be impossible to discover, to what causes the possible immunity of either one or other, or the destruction of either, or destruction of both alike, shall have been due. The high and loftily situated place is, cœteris paribus, likely to suffer most; but the shape of the "colline," as at Castelluccio, may be such with reference to the wave-path, and to what lies between it and the focus, that it may escape; and a place at its foot, like the Taberna D'Urma, be destroyed.
In a word, the result of my survey, over a wide and varied expanse of earthquake country is, that the grand modifying conditions of local effect are found in—
1st. Physical configuration of surface.
2nd. Physical configuration of formation in depth, such as transverse stratification, &c.
3rd. Elevation, as influencing continuity or isolation from surrounding masses, and admitting or not, of separate mass oscillation.
All these, in relation to the direction of wave-path, at the spot in question; and subordinate to these—
