322 
THE GEOLOGIST. 
more than one centre, and pierced by a siiccession of dikes, was 
already complete before the Vtil del Bove begiin to be foimed." 
The alluvial foi-mation on which Giarre and some other towns on 
the coast are built, attests the removal, at some unknown period, of a 
vast quantity of stony fragments from that part of Etna which lies 
immediately in the direction of the Val del Bove ; and if it could be 
sho'wn that this transported matter came down fi'om that gTeat 
valley, it would go far to prove that the abstraction of the missing 
rocks was for the most part effected by aqueous agency. On ex- 
amination it actually appears that the portion of this deposit, — which 
consists of coarsely stratified materials, with rounded and angular 
blocks some nine feet in diameter, but without striations or scratches 
like the " glacial di"ift" — opposite to the Val del Bove is conspicuous 
beyond the rest for its volume, and by being exclusively composed of 
the wreck of the volcano itself, the blocks being of trachyte, basalt, 
dolerite, grey-stone, and indeed of every variety of rock met with in 
the Val del Bove ; some being evidently derived from dikes. 
As usual. Sir Charles provides against attack by combatting the 
probable objections likely to be made to his notions. " It may," he 
says, " perhaps be suggested that the deposit at Giarre and Mangeno 
might have been swept down by rivers from the old cone when it 
was still entire, and before the caldera originated, in favour of which 
theory it might be urged that in the Val del Bove at present we dis- 
cover no action of running water capable of causing extensive 
denudation ; also that we may well imagine, dui-ing some former 
suspension of enaption on the eastern flank of the volcano, that 
ravines hke the Cava Grande may have been gradually excavated in 
the wide space separating the two hills of Calanna and of Caliato." 
In order to test the value of the hypothesis. Sir Charles explored 
from their lower to their upper terminations the two principal valleys 
of aqueous erosion, which slope upwards from the foot of the cone to 
the southern margin of the Caldera. Those who are conversant with 
Junghuhn's " Volcanos of Java" are well aware of the nature and 
I 
Lign. 3.— FiuTOWS of Aqueous Erosion on the Cone of Tengffcr. From Jimghung's "Java." 
value of this test ; for they will remember that the flanks of volcanic 
cones which are in full activity are free from furrows eaten out by 
running water ; whereas, such as have been long extinct, or are in a 
state of moderate activity, exhibit a great number of ravmes from 
300 to 600 feet deep, excavated by torrents, and parted from each 
