92 FRENCH CHALK. 
with finely powdered talc, and a certain portion of oil 
of benzoin. 
The Romans prepared a beautiful blue or purple 
colour, by combining pounded talc with the colouring 
fluid of some particular kinds of testaceous animals, 
that are found among the submarine rocks of the coasts 
of the Mediterranean. According to Tavernier, the 
French traveller, the Persians whiten the walls of their 
houses and gardens with lime, and then powder them 
with a silvery white kind of talc; which, he says, gives 
to them a very beautiful appearance. Talc is now used 
by the Chinese, and was formerly used by the Euro- 
peans, in medicine, 
,135. INDURATED TALC, or FRENCH CHALK, 
is a heavy mineral, of dose texture, and generally of greenish 
:grey colour; unctuous to the touchy and having a somewhat 
slaty fracture. 
It is found in a massive state; and leaves a zchite trace, 
when rubbed upon any object. 
This is a well known substance, which is in great 
request by carpenters, tailors, hat-makers, and others, 
as the lines that are drawn with it are not so easily 
effaced as those that are made with chalk, and particu- 
larly as they remain unaltered even under water. If 
lines be traced with it on glass, they remain invisible, or 
at least are scarcely perceptible by the naked eye, till 
breathed upon. This, it has been conjectured, in part 
depends on the comparative softness of the substance 
with which the impression is made ; the condensation 
of the breath taking place more readily on the glass 
than on the talc that covers it, and the impression of 
the talc becoming more apparent by the contrast. 
Indurated talc, when reduced to powder, is frequently 
employed for the purpose of removing stains, occasioned 
by grease, from silk and cloth. This it does effectually, 
and, in general, without injuring even the most delicate 
colour. Like potstone ? it is sometimes manufactured 
into culinary vessels. 
