Page:Great Neapolitan Earthquake of 1857.djvu/417

Rh the S. W. side of which, on the steep slope of Monte Mottola, the effects of the partial extinction of the wave at its surface as "a free or outlying stratum" were visible in considerable falls of projected rock (loose masses chiefly). Nothing of the wave passing along the flanking range reached the town, therefore, but secondary waves of refraction and dispersion, coming up from beneath the town, as the residue of the unextinguished original wave passed southwards.

Few better examples may be found, of the important effects of local condition, as modifying the effects of shock, or of the care necessary to observe and disentangle the phenomena. Of towns situated within three or four miles of each other, one is found almost totally destroyed, the other is scarcely injured. It seems inexplicable at first sight, that both should have been almost equally near, to the same subverting agency from beneath; yet nothing is simpler or more certain when explained, than the conditions which shielded the one, and left the other exposed to destruction.

The protecting circumstances as respects Diano will be understood by comparing Sketch No. 194 with the Section Sketch No. 195, supposing the line a b to be that of the wave-path.

St. Arsenio, Torre, and St. Pietro, small places on the west of the Vallone Diano, but north of Diano town, were also more or less protected by similar conditions; cut off from the great flank range, by the little lateral valley of the Aqua del Secchio, and others. They suffered much more than Diano, however, and St. Rufo, on the south flank of the lateral Valley del Torno, still more than either. The