[ 20 ] 
tains, in which they are found, and thefe manifeil alfo 
fome affinity in their ft iruSlure ; it feems moft reafonable 
to affign to both one common origin. The received 
notions, concerning the mode of origin of vulcanic hills, 
do not therefore feem intirely to correfpond with the 
phaenomena of Nature; fince naturalifts generally fup- 
pofe, that they have all been thrown up, from the bowels of 
the earth, by fubterraneous explofions, like the Monte 
di Cenere, near Puzzuoli, in the kingdom of Naples, the 
ifland of Santorino in the Archipelago, or the ejected en- 
trails of Vefuvius and^tna. But furely this muft appear 
a miftaken notion to any one who compares thefe tumul- 
tuary and inordinate aggregates, wdth the regular vulcanic 
organizations before defcribed. For in facft, what does 
Vefuvius, ^Etna, the Monte di Cenere, and fuch like 
eru6ted piles, prefent to us but a heap of ruins, which 
evidently manifeft the cafual and extraordinary caufe, to 
w hich they avowedly ow^e their origin ? But this origin 
feems irreconcileable with the regular ftrucftures before 
mentioned, as may perhaps fatisfadlorily appear, from 
my confiderations on the particular phaenomena, that 
characterize them. And though it is very poffible, that 
fuch organizations may fometimes take place upon the 
concretion of liquified matter thrown up in vulcanic 
eruptions ; yet, however fimilar they may he, from the 
nature of their origin, I can hardly imagine they can 
form other than imperfeCt and irregular maffies. For 
however wonderful the rivers of lava of Vefuvius or^t- 
na may appear to us ; they, in reality, are but partial and 
4 tumultuary 
