[ 3 ° 3 
tion, by that terrible volcano. Another proof that 
the real feat of the fire of volcanos lies even greatly 
below the general level of the country whence the 
mountain fprings, is, that was it only at an inconfi- 
derable depth below the bafis of the mountain, the 
quantity of matter thrown up would foon leave fb 
great a void immediately under it, that the mountain 
itfelf mufl: undoubtedly fink and difappear after a 
few eruptions. 
In the above accounts of the formation of the new 
mountain, we are told that the matter firft thrown 
up, was mud compofed of water and afhes, mixed 
with pumice dones and other burnt matter: on the 
road leading from Puzzole to Cuma, part of the 
cone of this mountain has been cut away to widen 
the road. I have there feen that its compofition is a 
tufa intermixed with pumice, fome of which are 
really of the fize of an ox, as mentioned in Toledo s 
account, and exactly of the fame nature as the tufa 
of which every other high ground in its neighbour- 
hood is compofed j fimilar alfo to that which covers 
Herculaneum. According to the above accounts, 
after the muddy fhower ceafed, it rained dry afhes : 
this circumflance will account for the flrata of loofe 
pumice and aflaes, that are generally upon the furface 
of all the tufas in this country, and which were moft 
probably thrown up in the fame manner. At the 
firfl: opening of the earth, in the plain near Puzzole, 
both accounts fay, that fprings of water burft forth ; 
this water, mixing with the allies, certainly occafioned 
the muddy fhower \ when the fprings were ex- 
haufted, there mufl; naturally have enfued a fliower 
of dry afhes and pumice, of which we have been 
likewife 
