[ r 7 ] 
eruption of this mountain, and of thevafl cavities there 
muft necellarily.be within its bowels. The moft ex-- 
tenfive lavas of Vefuvius do not exceed feven miles 
in length ; the operations of nature on the one moun- 
tain and the other are certainly the fame ; but on 
mount Etna, . all are upon a great fcale. As to the 
nature and quality of their lavas, they are much the 
fame; but I think thofe of Etna rather blacker, and 
in general more porous, than thofe of Vefuvius. In 
the parts of Etna that we went over I faw no ftratas 
of pumice ftones, which are frequent near Vefuvius, . 
and cover the ancient city of Pompeia ; but our 
guide told us, that there are fuch in other parts of the 
mountain. I faw fome ftratas of what is called here 
TufFa, it is the fame that covers Herculaneum, and 
that compofes moft of the high grounds about Naples; 
it is upon examination a mixture of fmall pumice 
ftones, afhes, and fragments of kva, which is by 
time hardened into a fort of done. In fhort I found, . 
with refpeft to the matter erupted, nothing on mount 
Etna that Vefuvius does not produce, and there cer- 
tainly is a much greater variety in the erupted matter 
and lavas of the latter, than of the former; both 
abound with pyrites and cryftallizations, or rather 
vitrifications. The fea fhore at the foot of Etna, in- 
deed, abounds with amber, of which there is none 
found at the foot of Vefuvius. At prefent there is a 
much greater quantity of fulphur and falls on the 
top of Vefuvius than on that of Etna ; but this cir- 
cumftance varies according to the degree of fer- 
mentation within, and our guide allured me he had 
feen greater quantities on Etna at other times. In 
our way back to Catania, the canon (hewed me,, a 
Voi.. LX. D little 
