( ^33 ) . 
Mount Vefuvks has fpued out a vaft quantity of Ailies. 
The great Rains that faH upon thefe Afli'es makes a 
fort of Lees, which kft in the hollow places are eva- 
porated by the heat of the Sun, and there remains this 
Urinous Salt, whofe tafte is fome thing like Sal Armo- 
niac. It was very hard and folid, but I found it began 
to be moift in wet weather, fo I keep it clofe in a 
Bladder. 
Alumen. 
Atxthe Sulfatara between Ncij)les and Pnzzolo they 
make Alum in this manner. In Summer time they ga- 
ther as much as they have occafion for of an Earth 
that is there in the middle of a large Area, and they 
keep it in a dry place. They put it in Lead Coppers of 
a good thicknefs^and powr upon k Hain- water, which 
is alfo impregnated with the fame Mineral. For that 
purpofe they take great care to dig fome large holes to 
preierve in them the Rain-water, and they carry it to 
a large Ciftern by the Coppers. There is now fix of 
thefe, two large ones, and four of a leffer fize. They 
takeaway the Earth when the Lixivmm is made, and 
as it grows ftronger by Evaporation, they put it from 
one Copper into another, till it is fufficiently evaporated. 
Then they take it out and convey it iiito a wooden 
Tub, where after it is cool'd, you fee the Alum ftick 
to the fides in the form oi Cryftals. But the moft re- 
markable thing is, that thefe Coppers are plac'd upon 
fome of the great Spiracffla^ and that without any ex- 
pence in fuel, only by the violent heat of thefe efflu- 
via the Evaporation is conftantly made fuiSeient for 
that Criftallization. All this Laboratory where arc 
the Coppers and the Ciftern, with the Tubs is only 
til'd over. The Governours of the great Hofpical of 
tk?, A>niHncuita^ who have been at the Charge of this 
ingenious Contrivance, do make now about three or 
four hundred pounds a year by it. 
