CHAPTER L.
BACK TO NAPLES—VESUVIUS—JOURNEY OF OBSERVATION TO ROME THROUGH THE PONTINE MARSHES.
While waiting for my passport, I ascended Vesuvius, and examined with some care the courses of several of the ancient and the very recent lava currents, with a view to the theory of their movements.
At Resina and Vesuvius, I found that the town of Ottajano, had suffered considerable fissuring, (more, I was informed, than Nola); and that the shocks had been felt in two different directions, crossing each other—the one the same as at Naples and all about here, viz., nearly south to north; and the other in the direction pointing to Vesuvius, or, as they said, the shock "came from Vesuvius." This would be a wave-path nearly 40° E. of north, and would appear to be a secondary wave propagated from Vesuvius by the oscillation of the mountain as a mass, from the effect of the primary shock acting on it south to north, and ending in gyratory oscillation of the cone, transmitted to its base around. It might, however also, be a reflected wave, from the direct wave, of low intensity, reaching Vesuvius and the plain to the east and S.E. of it, immediately from the focus, in a direct line.
Finding that the earthquake was stated to have been felt along the coast, northward and westward, as far as Terra-
