134 Mr. G. P. Scrope on the Formation of Craters, 
wanting in the Val di Bué, and left in their place craters of cor- 
responding dimensions. 
Sir Charles Lyell suggests (as others have done before him), 
in regard to some of the largest known craters, another possible 
origin, which he calls Engulfment—that is, the subsidence of 
the upper part, or a large area, of a voleanic mountain into some 
abyss suddenly opened beneath. With respect to this suppo- 
sition, without attempting to dispute its possibility, 1 must say 
that I am not aware of any such process having been ever wit- 
nessed by any credible observer so placed as to be able to distin- 
guish between engulfment and ejection ; and consequently that 
it were well to be cautious in admitting the occurrence of such 
a phenomenon, if the ordinary mode of action be sufficient to 
explain the facts really observed. We possess reports, it is true, 
of eruptions and earthquakes in Java, Sumatra, the Andes, and 
elsewhere, having caused the disappearance of the entire summit 
of a mountain, leaving a vast cavity in its place. But this is 
precisely the result that was observable after the eruption of 
Vesuvius in 1822. And in that instance we know there was no 
subsidence. The leading example usually adduced of such im- 
mense (supposed) engulfments is the truncation of the lofty cone 
of Papandayang, in Java, by an eruption in the year 1772. 
There, it is always said, a great area of the volcano “ fell in and 
disappeared,” swallowed up in the bowels of the earth, together 
with forty villages and their inhabitants. Such are the phrases 
usually made use of on these occasions, and very naturally so, 
by alarmed and unscientific observers. But recent explorers, 
especially Professor Junghuhn, have stated that these towns and 
villages of Papandayang were not swallowed up at all, but buried, 
like Pompeii, under the ejectamenta of the volcano; and Dr. 
Junghuhn, therefore, very properly refers the truncation of the 
mountain to eruptive explosions, rather than to subsidence. 
It is, no doubt, quite conceivable, that within a volcanic 
mountain some internal reservoir, or subterranean lake of liquified 
lava, coated over by a coat of hardened rock or the accumula- 
tion of fragmentary matter, may be tapped, as it were, by an 
earthquake, and empty itself out of an aperture in the side of 
the mountain at a low level, leaving a cavity, which another 
earthquake, or the explosion of vapour and gases accumulated 
within it and increasing in temperature, may cause to burst like 
a vast bubble,—the overlying crust of rocks falling inwards. 
But such a supposition is, in the present state of our knowledge, 
purely conjectural, and unwarranted, if, as I have endeavoured 
to show, the ordinary phenomena of eruption suffice to account 
for the formation of the largest known craters. If it is to be 
resorted to in any case, it would be perhaps in that of the very 
