SULPIIAT OF BARYTES. BONONIAN STONE. 121 
tenacious cement ; and painters use a preparation that 
is made from it as a white colour which will not 
change. This is sold in the shops under the name of 
" Hume's permanent white." Barytes taken into the 
stomach proves a virulent poison ; yet a preparation of 
it is used in medicine, and particularly for the removal 
of scrophulous complaints. When finely pounded and 
mixed with oatmeal, carbovat of barytes has been found 
an efficacious poison for rats. 
196. SULPHAT of BARYTES is a mineral formed by 
the combination of sulphuric acid (24) with barytes. 
It sometimes occurs in a state of powder, frequently in 
shapeless masses , and often crystallized: the primitive form of 
its crystals being a four-sided prism. It is not soluble in any 
other than sulphuric acid. 
With us sulphat of barytes is of no use in the arts. 
The Chinese, however, employ it as an ingredient in 
the composition of porcelain ; and it is said to form a 
good manure for clover fields. 
The BOLOGNA PHOSPHORUS, or BONONIAN STONE, 
a very remarkable land of barytcs, has its name from 
being found near Bologna in Italy. This substance, 
when detached, is usually observed in roundish, flat, 
kidney-shaped pieces, from about the size of a walnut 
to that of an orange, which have a shining and some- 
what fibrous texture within. 
When the outer coat of this stone is washed away by 
heavy rains, it has sometimes the appearance of bur- 
nished silver. An Italian shoemaker, in the year 1630, 
deceived by this appearance, carried home several 
pieces, hoping, by means of fire, to extract silver from 
them. But at the same time that he was disappointed 
in this expectation, he was surprised by a very unlooked- 
for phenomenon. All the pieces which he had thus 
attempted to melt, when they were afterwards exposed 
to the light, became themselves luminous. It is the 
singular property of the Bologna phosphorus, after it 
has undergone calcination in a particular manner, to 
VOL. I. G 
