Somma, the broken crest of a greater and earlier volcanic crater, has been unmoved in place, unchanged in form and height, through eighteen centuries; a grand and awful fragment left after the poetic 'struggle of earth and sky,' and full of peculiar records of the combat. Vesuvius, born of Somma, and seated within the encircling grasp of its parent, is a variable heap thrown up from time to time, and again, not seldom, by a greater effort of the same force, tossed away into air. . . . Thus two classes of forms arise in the history of Vesuvius: one may be called the old or Somma form, left after violent and exhaustive efforts of the volcano; the other the new form, in which Vesuvius takes a place unrecorded in ancient history (p. 174).

Nothing is more certain than the fact that the Vesuvius upon which the ancient Romans and the Greek settlers of southern Italy looked, was a mountain differing entirely in its form and appearance from that with which we are familiar. The Vesuvius known to the ancients was a great truncated cone, having a diameter at its base of eight or nine miles, and a height of about