84 
NEWER PLIOCENE PERIOD. 
[Cli. VII. 
depth that they expose to view a great part of the structure of 
the entire mass, which, in the Val del Bove, is laid open to the 
depth of from four thousand to five thousand feet from the 
summit of Etna. The geologist thus enjoys an opportunity 
of ascertaining how far the internal conformation of the cone 
corresponds with what he might have anticipated as the result 
of that mode of increase which has been witnessed during the 
historical era. 
It is clear, from what we before said of the gradual manner 
in which the principal cone increases, partly by streams of lava 
and showers of volcanic ashes ejected from the summit, partly 
by the throwing up of minor hills and the issuing of Java-cur- 
rents on the flanks of the mountain, that the whole cone must 
consist of a series of cones enveloping others, the regularity of 
each being only interrupted by the interference of the lateral 
volcanos. 
We might, therefore, have anticipated that a section of Etna, 
as exposed in a ravine which should begin near the summit and 
extend nearly to the sea, would correspond very closely to the 
section of the ancient Vesuvius, commencing with the escarp- 
ment of Somma, and ending with the Fossa Grande ; but with 
this difference, that where the ravine intersects the woody 
region of Etna, indications must appear of changes brought 
about by lateral eruptions. Now the section before alluded to, 
which can be traced from the head of the Val del Bove to the 
inferior borders of the woody region, fully answers such ex- 
pectations. We find, almost everywhere, a series of layers of 
tuff and breccia interstratified with lavas, which slope gently to 
the sea, at an angle of from twenty to thirty degrees ; and as 
we rise to the parallel of the zone of lateral eruptions, and still 
more as we approach the summit, we discover indications of 
disturbances, occasioned by the passage of lava from below, 
and the successive inhumation of lateral cones. 
Val di Calanna. — On leaving Zaffarana, on the borders of 
the fertile region, we enter the ravine-like valley of St. Gia- 
como, and see on the north side, or on our right as we ascend, 
