no Sir William Hamilton’s Account of 
Naples to the refiners of metals ; at first it was sold for about 
six pence a pound, but, from its abundance, the price is now 
reduced to half that money ; and a much greater quantity must 
have escaped in the air by evaporation. 
The situation of Mount Vesuvius so near a great capital, 
and the facility of approaching it, has certainly afforded more 
opportunities of watching the operations of an active volcano, 
and of making observations upon it, than any other volcano on 
the face of the earth has allowed of. The Vesuvian diary, 
which by my care has now been kept with great exactness, and 
without interruption for more than 15 years, by the worthy 
and ingenious Padre Antonio Piaggi, as mentioned in the 
beginning of this letter, and which it is my intention to de- 
posite in the library of the Royal Society, will also throw a 
great light upon this curious subject. But as there is every 
reason to believe,, with Seneca,* that the seat of the fire that 
causes these eruptions of volcanoes is by no means superficial, 
but lies deep in the bowels of the earth, and where no eye can 
penetrate, it will, I fear, be ever much beyond the reach of 
the limited human understanding to account for them with 
any degree of accuracy. There are modern philosophers who 
propose, with as great confidence, the erecting of conductors 
to prevent the bad effects of earthquakes and volcanoes, and 
who promise themselves the same success as that which has at- 
tended Doctor Franklin’s conductors of lightning; for, as 
they say, all proceed from one and the same cause, electricity. 
When we reflect how many parts of the earth already inha- 
bited have evidently been thrown up from the bottom of the 
* “ Non ipse ex se est, sed in aliqua inferna valle conceptus exaestuat, et alibi pas- 
'•* citur j in ipso monte non alimentum bnbet, sed viam .” — Seneca, Epist. 79. 
