SILVER. 
4<j6 
of the most singular mines in this quarter of the 
globe. The district in which it is situated is 
mountainous ; and the mines are divided into su- 
perior and inferior, on account of their relative po- 
sition. The earth is composed of beds nearly in a 
vertical position, and running from north to south. 
Some are composed of quartz mixed with mica, of 
granite, and of chalk ; while others are formed of 
whitish-gray quartz, mixed with fine blackish mica, 
or else consist of ferruginous rock. These beds are 
of very considerable thickness, and contain a great 
quantity of native as well as of mineralized silver. 
Brogniart remarks that the veins are richer in mi- 
neral, and their produce more considerable, where 
they traverse the beds of ferruginous rock, than in 
any other part. 
The greatest depth of these mines is about two 
hundred and seventy yards, and enormous masses 
of native silver are said to be found within them. 
“ The annual produce about the year 3 76*8,” says 
Brogniart, was two hundred and twenty myria- 
grammes of silver.” 
The mines of France are interesting rather on 
account of the mineralogieal substances which they 
produce, than from the quantity of silver they con- 
tain. The mine of A 1 lemon t, ten leagues from 
Grenoble, is one of the principal, and was dis- 
covered in the year 1763. It is in a very elevated 
situation, being no less than two thousand eight 
hundred yards above the level of the sea, towards 
the top of a mountain composed of micaceous rock. 
