File:The Quarterly journal of the Geological Society of London (12981479134).jpg

1859..
SCKOPE — COliTES AND CRATEKS.
517
and the terminal cone of Etna to be eruptive cones *. But, on the
other hand, M. de Buch, in the passage I have already referred to,
affirms the extreme regularity of the entire figure of Etna to be a
proof that it could not be the product of eruptions, but must have
been upheaved at a single stroke, '^a V instant meme de sanaissancef.^'
In fact, M. de Buch's test is the precise reverse of M. de Beaumont's.
Suppose, however, we take M. de Beaumont's as that of the latest
authority on the point. Surely it is trifling with the subject to rest
so important a distinction as to origin upon a difference in outline
so slight, so disputable, nay, so necessarily variable under varying
circumstances of composition, dilapidation, &c., independently of all
question of origin. In the first place too, it is undeniable that
many, perhaps the majority of the acknowledged cones of eruption
about Etna, and in Central France, show a sloping outline by no
means '^ rectilinear," but sweeping downwards in a gradual curve
that lessens in steepness till it meets the base, which is M. de Beau-
mont's characteristic of an " upheaved cone." In the second place,
the slightest consideration makes it obvious that great differences in
this respect must be occasioned by casual differences in the size,
shape, or mineral character of the ejected fragments, by their more
or less heated state and consequent coherence or non- coherence at
the time of their fall and accumulation, by their greater or less degra-
dation by storms of rain accompanying the eruption, or by a longer
or shorter subsequent exposure to atmospheric influences. In the
case of the larger volcanic mountains, if we suppose them the pro-
duct of repeated eruptions, a graduated slope towards the base must
necessarily have been occasioned, not only by longer exposure to the
agents of degradation, but still more by the accumulation of the
lavas and scorioe emitted from lateral vents on the lower flanks of
the mountain. Indeed, M. de Beaumont, by admitting the many
Fig. 5. — Outline of Etna, as seen from near Catania. (From Mem.
Soc. Geol. de France, vol. iv. pi. 2.)
hundred parasitic cones of Etna and their lava-streams to be eruptive,
himself accounts, on the theory of accumulation, not of upheaval, for
the graduated slope of the mountain as a whole into the plain
around. And, in truth, the visible portion of his central up-

• Memoires, iv. p. 157.