CLASS IL SALTS. 
ORDER I. EARTHY SALTS. 
ALUMINE FAMILY. 
19?. ALUM is a substance of yellowish or greyish white 
colour, usually opaque, but sometimes transparent. When 
purified, it consists of slender, irregular, hair-shaped fibres, 
and has a sweetish, astringent taste. 
The alum of commerce is an artificial production 
from the different kinds of stones which contain it. That 
called Roman alum, from its being procured from the 
neighbourhood of Rome, ifc usually considered prefer- 
able to the other sorts ; but good alum of our own ma- 
nufacture is equal to it in quality. The Levant, or 
Roche alum, is said to have had its name from the vil- 
lage of Rocca, the present Edessa, in Syria. 
There is a famous alum mine at Tolfa, near Civita 
Vecchia, in Italy. The alum is obtained from this mine 
nearly in a pure state ; and it is so extremely hard, that 
it can only be wrought by means of pickaxes, and gun- 
powder. At Solfatara, near Naples, and in other vol- 
canic countries, an abundance of alum is found, in a 
state of efflorescence, from the lava. 
The alum of our own country is manufactured from 
a kind of slaty stone which is found near Whitby, in 
Yorkshire. This manufactory was first established about 
the conclusion of the sixteenth century, by Sir Thomas 
Chaloner, who is supposed to have obtained his know- 
ledge of the process, from the alum works which had 
then lately been introduced into Germany and Spain. 
The rock of alum slate, near Whitby, is supposed to 
be nearly twelve miles in extent : and affords an abun- 
dant supply of alum. The workmen tear open the 
