Page:Great Neapolitan Earthquake of 1857.djvu/235

Rh four metres in diameter; and in the southern summit, called Sierra della Croce, the strata being laid bare by several hollows, show an inclination of 47 degrees; and from this side rises another opposite summit, having the same inclination, from which we may conjecture that the Sierra della Croce has been separated from it. Therefore, even supposing we admit that the internal impulse accompanying the fires of the Vulture, having its centre in the neighbouring lakes of Monticchio, may have extended to a great distance, it is impossible that the actual arrangement of stratification of the Macigno of Monteverde could have been occasioned by it: an order not essentially different from that of the stratified rocks which are displayed from Melfi to Rionero.

In the district of the Vulture, much better than in any other volcanic region of our kingdom, we can observe the manner in which the volcanic rocks interstratify with the neptunian; and, comparing them with the observations here collected, we cannot reconcile them with the idea that volcanic forces could have had so extensive a field of action near the terrestrial surface. On the contrary, we are led to the opposite opinion, namely, that the space is very limited in which volcanic explosions can occasion elevations or other perturbations of ground, and that the first convulsions are almost always concocted under the materials which are subsequently ejected. As we must return to this argument in another part of our work, what we have already said is sufficient to testify, that in our opinion the volcanoes of the Vulture have had no part in the elevation of the rocks of the second series, in which they have appeared.

The relation of arrangement between these rocks and the Apennine limestone presents another field of inquiry, in which it is not easy to see clearly. Is it beyond a doubt that the former belong to a period subsequent to the latter? Are the elevations of the first cotemporary with the elevation of the second? Have they been once or oftener convulsed? What difference of conditions results from the difference of composition between the rocks of the first and second series? These are the principal questions which the geologist is compelled to discuss. We shall speak of the last when we have given the necessary mineralogical description of