132 Mr. G. P. Scrope on the Formation of Craters, 
to “ craters of eruption,” can only lead to a wrong conception 
of the originating forces. 
Where, indeed, is to be found a crater, the formation of which 
cannot be accounted for (making allowance for the subsequent 
modifications already referred to) by eruptive phenomena of the 
same character as those which have before the eyes of trustworthy 
observers repeatedly drilled enormous craters through the axis 
of the cone of Vesuvius ? 
Is it the vast size of some craters which should render such 
an origin incredible in their instances? For example,—of the 
Val di Bué on the flank of Etna, the Caldera of Teneriffe, that 
of Palma, Santorini, or the exterual crater of Barren Island ; 
which measure some three, five, or even six miles in diameter ? 
But the crater of Vesuvius, formed in 1822, before my eyes, by 
explosions lasting twenty days, measured a mile in diameter, and 
was more than a thousand feet deep. The old crater of Somma, 
which half encircles the cone of Vesuvius, is about three times 
as wide as the crater of 1822. Are we, then, on that account 
alone, to believe that it could not have been produced by an 
eruption of proportionately greater violence,—when, too, such 
an eruption is known to have occurred about the time this crater 
must have been formed, namely, in the year 79, and to have 
overwhelmed three cities at the base of the mountain beneath 
its enormous fragmentary ejections? Is it not, on the contrary, 
much more in accordance with sound philosophy to ascribe the 
excavation of the old concentric crater of Somma to the same 
cause which but the other day was seen to excavate the new 
crater of Vesuvius, through the heart of the same mountain, 
than to invent for the former a different and fanciful process? 
But if Somma be admitted, notwithstanding its extent, to be a 
true crater of eruption, the same origin cannot be denied to that 
of Palma, Santorini, or others, on the ground of their size, which 
scarcely, if at all, exceeds that of Somma. 
Sir Charles Lyell seems to doubt the Val di Bué being a true 
crater of eruption upon two grounds. First, because the beds 
composing the surrounding cliffs do not show the usual qua- 
qua-versal dip, but generally slope towards the sea. This, how- 
ever, is merely the result of the eruption having broken out on 
one side of the central axis of the mountain,—a circumstance of 
frequent occurrence ; and naturally so, because the old central 
vent is apt to be sealed up by the conaolidated products of former 
eruptions, and the point of least resistance to the subterranean 
eruptive force will often, therefore, be a little on one side,— 
probably on a fresh point of a fissure broken through the flank 
of the mountain. 
In fact, there must be a contest between the resisting powers of 
