Page:Great Neapolitan Earthquake of 1857.djvu/351

Rh the underlying summits of the breccia mountains, and the flanking chains beyond; and in these, as well as in the bottom of the main valley, a great depth of loose material is deposited, chiefly heavy calcareous clays and boulders. These are deeply cut into by the lateral torrents, and still more deeply by the Tanagro itself, which here rolls over a bed wholly of rounded boulders, the skeleton of the washed-away detritus.

It is not easy here, or indeed anywhere else in the Southern Apennines, to imagine the train of causation (upon any of the usually accepted views of elevation) that led to this formation. It seems probable, however, that before this upper part of the valley assumed its present character, the surface of the breccia occupied something of the line $$dd$$, &c., if not one still higher, and that enormous masses have been removed by denudation, between those which now form the opposite ranges of "Collines." As respects our immediate subject, it will be obvious that any earthquake shock, emergent from the eastward at a steep angle, must arrive, through an immense thickness of beds of limestone first, and of breccia afterwards, before reaching the surface; and hence with vast loss of vis vivâ, and buffed, as to much of its destructive power.

I was unable to attempt determining, whether the breccia beds lie directly upon the limestone at both sides of the valley, or may have some other thin beds interposed. But I think the first is the fact.

The military road of Campostrina, over the rampart that separates the valleys of the Tanagro and of the Calore (as its higher stream now is called), is led over the mountain at the eastern side of the river gorge, winding round