320 
THE GEOLOGIST. 
crystalline lavas, whether tracliytic or doleritic, whether slightly or 
steeply inclined, been in great pai't intrusive, they would have altei'ed 
the tuffs as much ahove as below them. Moreover, they must have 
given rise to innumerable faults ; for while they vary in thickness 
from 3 to GO feet, they are not persistent for indefinite distances, but 
often thin out rapidly in both directions. They ought therefore, had 
they been injected, to have lifted up the incumbent deposits partially, 
so as to give rise to many conspicuous faults. For these reasons, I 
can not adopt the conclusion that the upheaval of Etna has been 
largely due to the injection of lavas in sheets parallel or conformable 
to the tulfs and fragmentary materials." 
M. Elie de Beaumont in his celebrated essay on Mount Etna 
insists on the uniformity in thickness and parallelism of the many 
hundreds of lava-beds which are presented on the escarpments of 
the Val del Bove, and on their continuity for gi-eat distances, as facts 
confirmatory of the doctrine of their original horizontality and sub- 
sequent upheaval into their present positions, referring their occa- 
sional steep inclinations to their liability to be bent together, like 
the regular sedimentary strata which have undergone flexures in 
mountain-chains. This assertion has not escaped the keen observa- 
tion of Sir Charles Lyell, and consequently we have a portion of 
his paper devoted to the evidence of pseudo-parallelism and the want 
of uniform thickness of the beds forming the escarpments of the Val 
del Bove. A conspicuous selected case of want of unifonnity in 
thickness of stony layers in the northern escarpment — one bed 
Lign. 2.— Non-parallel Lavas. Want of Uniformity in Thickness of Stony Layers in 
Northern Escarpment of the Val del Bove. 
attaining forty-feet in its thickest part — and instances of non-parallel 
strata to the south of Finocchio Inferiore, and at the Serradel Solfizio, 
with an example of curvatures in the lavas of Zoccolaro effectually 
Lign. 3. — Curvatures of the Lavas of Zoccalaro. 
dispose of this point, and leave remaining only the easy task of 
proving the analagous fonn and arrangement of the ancient and 
modern lavas. 
The third part of Sir Charles's paper is devoted to the relation of 
the volcanic rocks of Mount Etna to the associated alluvial and 
modern tertiaiy deposits of Giarre 
