I do not doubt but that I fhall convince you^ 
as I am myfelf convinced, that the whole circuit 
(lb far as 1 have examined) within the boundaries 
marked in the map, is wholly and totally the pro- 
duction of fubterraneous fires ; and that mold probably 
the fea formerly reached the mountains that lie be- 
hind Capua and Caferta, and are a continuation of 
the Appennines. If I may be allowed to compare 
fmall things with great, I imagine the fubterraneous 
fires to have worked in this country under the bottom 
of the fea, as moles in a field, throwing up here and 
there a hillock, and that the matter thrown out of 
fome of thefe hillocks formed into fettled volcanos, 
filling up the fpace between one and the other, has 
compofed this part of the continent, and many of the 
illands adjoining. 
From the obfervations I have made upon mount 
Etna, VefuvLus, and its neighbourhood, I dare fay, 
that, after a careful examination, moft mountains 
that are, or have been volcanos, would be found 
to owe their exifience to fubterraneous fire ; the 
direCl reverfe of what I find the commonly received 
opinion. 
Nature, though varied, is certainly in general uni- 
form in her operations ; and 1 cannot conceive that 
two fuch confiderable volcanos as Etna and Vefuvius 
fliould have been formed otherwife, than every other 
confiderable volcano of the known world. I do 
not wonder that fo little progrefs has been made 
in the improvement of natural hifiory, and parti- 
cularly in that branch of it which regards the 
theory of the earth; nature acls fiowly, it is difficult 
to catch her in the fadt, Thofe who have made this 
fubject 
