SILVER. 
499 
size, traverses a slaty mountain, and encloses within 
its stony bed a great quantity of native and mi- 
neralized silver, besides a little gold. According to 
Brongniart, the annual produce of silver and gold 
amounts to about 12,500,000 francs. The mine is 
said to be 600 yards deep, and there still remains 
a vein untouched, which is supposed to contain 
alone as much silver as all the other mines of New 
Spain. 
Silver possesses all the metallic properties of other 
perfect metals, and is fixed and unalterable in the 
fire of our ordinary furnaces. But this quality 
must be understood with some limitation, as it only 
relates to the degree of intensity and violent action 
of the fire. Daily experience proves that this 
metal may be volatilized, as we frequently find it 
in the soot of chimneys, where they are in the 
habit of melting large quantities of silver. Besides 
which, when exposed to the focus of the most 
powerful burning glasses, such as Mr. Parker’s, it 
evaporates in a very sensible fume, that rises five or 
six inches, and completely silvers a plate of metal 
exposed to its influence. Patrin remarks that in 
these experiments, where gold and silver is thus 
melted by the solar rays, the globules of metal ac- 
quire a very rapid giratory motion. 
Silver is the most ductile of all metals, except 
gold. A single grain of silver may be extended 
into a plate of 1 2 6 inches long, and half an inch 
broad : if the grain be reduced into leaves under 
2 K 2 
