Archibald Geikie and Thomas Ashby

“ Vesuvius consists of two distinct portions. On the northern side a lofty semicircular cliff, reaching a height of 3714 ft., half encircles the present active cone, and descends in long slopes towards the plains below. This precipice, known as Monte Somma, forms the wall of an ancient prehistoric crater of vastly greater size than that of the present volcano. The continuation of the same wall round its southern half has been in great measure obliterated by the operations of the modern vent, which has built a younger cone upon it, and is gradually filling up the hollow of the prehistoric crater. ”

“ At Pompeii, for example, among other devastation, the temple of Isis was shaken into ruins, and, as an inscription records, it was rebuilt from the foundations by the munificence of a private citizen. On the 24th of August 79 the earthquakes, which had been growing more violent, culminated in a tremendous explosion of Vesuvius. ”

“ The modern cone of the mountain has been built up by successive discharges of lava and fragmentary materials round a vent of eruption, which lies a little south of the centre of the prehistoric crater. ”