If the line passing through those three grand centres of volcanic action—Vultur, Vesuvius, and Epomeo—be produced to the westward, it will strike the very interesting igneous masses of the Ponza Islands. These insignificant islands, which, from the early Roman times down to the present day, have figured in history only as places of banishment for criminals, possess for the geologist the very highest interest. This is due not only to the wonderful characters of the rock-masses which compose them, but also to the admirable manner in which these are exposed to our study by the extreme denudation to which they have been subjected.