224 Sir C. Lyell on the Conical Form of Volcanoes. 
equalities on its surface, appearing almost even when contrasted 
with the main current of the same date, from the surface of 
which many parallel and longitudinal ridges project prominent- 
_ ly, sometimes 40 feet above their base, and with very steep sides 
sloping at angles of from 85° to 70°. The dip of the main cur- 
rent is between 10° and 16° east. From this and other exam- 
ples, it is inferred that wherever the slopes are excessive (between 
25° and 45°) the surfaces of the cooling lavas are less rugged 
than where the melted matter has congealed on more level 
ground, 
Allusion was next made to some lavas which have cascaded 
over sea-cliffs 500 feet high, between Aci Reale and Santa Tecla. 
One of these at a place called the Scalazza of Aci Reale, exhibits 
a longitudinal section of a tabular mass of stony rock 20 feet 
thick, inclined at angles of 23° and 29°, which is connected un- 
interruptedly with the main body of the same lava resting on 
the gently sloping platform above, of which the sea-cliff is the 
abrupt termination. The above-mentioned highly inclined stony 
lava is covered as usual by a parallel layer of scorize (in this case 
12 feet thick) and its base consists of another bed of scorie of 
— thickness. 
; veral other sections of modern lavas of Etna, which have not 
near Zafarana; and another reposing on the face of the great 
precipice at the head of the Val del Bove, under the sunk space 
ed “The Cisterna.” This remarkable current has a mean 
the stream have been undermined and denuded by that constant 
waste which makes the innumerable dikes to stand out in reli 
on all the precipices surrounding the Val del Bove. Perhaps, 
also, in this instance, the lateral excavation of the lava may have 
been assisted by a rush of water like that of 1755, commonly 
led Recupero’s flood, which descended the same precipice, the 
“ Balzo di Trifoglietto.” Suggestions were then offered on t 
oes cause of that singular inundation, which swept in a few 
from near the summit of Etna through the Val del Bove 
to the sea. The Canon Recupero traced its course, a few 
months after the event, by following the line of sand and boul- 
ders which it had left in its track; and calculated that the vol- 
ume of water was so great, that, had all the snows of the top of 
