Page:Great Neapolitan Earthquake of 1857.djvu/233

Rh attributed the actual position of strata inclined to the horizon to elevation, this does not exclude the idea of undermining operations. And since, whether they have been elevated or whether they have been undermined, we should always find their primitive horizontal position deranged in the same manner, it is not easy to decide which of the two conditions has rendered the region mountainous, or, if both were in operation, which of the two has had the greater influence. For if we consider the general physical property of matter to diminish in volume by the decrease of its temperature, the theory at present held by all, of the primitive state of igneous fusion of our planet, leads us to the necessary consequence, that in cooling it must have diminished in size, and the forces which have acted on its consolidated crust must induce it to approach the centre. In the district occupied by the volcanoes of the Vulture, other particular considerations present themselves to the mind of the geologist who contemplates the strata of the neptunian rocks, here, perhaps, more elevated than elsewhere. As we shall presently state, these volcanoes are surrounded on every side by hills, formed of rocks of the second and third series, which must have felt the effects of the disturbing volcanic eruptions, and therefore it is easy to attribute their elevation to the same eruptions. In the east side of the base of Mount Vulture, along the line occupied by the cities of Melfi, Rapolla, Barili, and Rionero, in many places it is easy to observe the strata of limestone and red marl beneath the lavas and volcanic conglomerates, with the ordinary character of elevation proper to this formation. Half way on the road between Rionero and Barili, on the left-hand side going from Rionero, in the place denominated the Valle del Salice, a long series of the outcrops of stratified rocks, which form the bed of a brook which flows over them, is seen. The average of their inclination, though variable, is about 70 degrees, and they are elevated from the side turned towards the east and south-east. It is enough to say that they are inclined in a contrary direction to the slope of the Vulture, to prove it impossible to attribute their elevation to an internal force, whose centre of action should coincide with the central part of the volcano. The same thing may be observed in many places on the same road, so that this