Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/450

Rh of cones; but whose nature must be such, as is called locally and spasmodically into action, now most energetically at one point, now at another of the same line, but yet is never exhausted at any?

The discovery of the real nature of this cause will be the key to all true knowledge, both of volcanic action, which is only its symptom, and of all the forces that have produced, and do produce, the elevations, or, to speak more correctly, the changes of level of the surface, of our own and that of other planets. Earthquakes, then, demand to be regarded, not as themselves agents of permanent elevation of the land, which they cannot be at all, and with respect to which, even the greatest volcanic efforts (accumulated cones) upon our globe, are mere skin-deep phenomena. We must regard seismic and volcanic phenomena as both unequal effects and local evidences of a wide-spread, and constantly, but unequally acting, yet always active force, resulting in elevation; which is not evidenced indifferently all over the surface of the globe, but is mainly confined to broad bands conforming to its mountain ranges.