of the famous quicksilver mine at Aid Al- 
maden. The mineral obtained here is the 
ruby silver ore. But it is in the centre of 
the Andes, in situations which, though im- 
mediately exposed to the peri)endicHlar 
rays of the sun, are constantly covered with 
snow, that nature has most abundantly dis- 
tributed this metal. In twenty degrees of 
southern latitude, within the torrid zone, 
we find the famous mountain- of Potosi, 
situated near the source of the Rio de la 
Plata. This mountain is one of the most 
considerable in Peru ; its height is immense ; 
and it appears from the description of, tra- 
vellers, that from top to bottom it is full of 
veins of silver. When these mines were first 
discovered, in the year 1545, the veins were 
so rich as to be almost entirely composed of 
silver without any mixture. At present, 
however, the produce is very different, 
scarcely more than five drams being obtain- 
ed from a hundred weight of ore ; still, from 
the great abundance of mineral, the pro- 
duce is very considerable. According to 
the observations of several Spanisli natura- 
lists, the mountain of Potosi alone, from 
the time it was first discovered, in 1545, till 
the year 1638, that is in the space of ninety- 
three years, yielded four hundred millions 
of pesos, or ounces of silver. 
The analysis of silver ore varies accord- 
ing to its nature and combinations. Native 
silver, after being broken down and washed, 
is rubbed with liquid mercury, which by 
strong trituration dissolves and combines 
with the silver. This amalgam is subjected 
to pressure, to separate the excess of mer- 
cury. It is then distilled, and afterwards 
heated in a crucible, to volatilize the mer- 
cury, and the silver remains pure. When 
silver is combined witli antimony and sul- 
phur, the ore is to be strongly roasted, to 
separate the antimony or sulphur. It is 
then melted with a proper quantity of alka- 
line flux. The sulphurated oxide of silver 
and antimony may be treated in the same 
way. See Assaying. 
Silver is of a fine white colour and great 
brilliancy. The specific gravity is 10.4, and 
according to some, when it is hammered, 
10.5, and sometimes nearly 11. The hard- 
ness of silver is intermediate between iron 
and gold. The elasticity of silver is consi- 
derable, and it is one of the most sonorous 
of the metals. It possesses very great duc- 
tility and malleability. It may be beaten 
out into leaves of of an inch thick, 
and a grain of silver may be so extended as 
to be formed into a hemispherical vessel of 
sufficient capacity to hold an ounce of wa- 
ter, or to be drawn out into a wire four 
hundred feet in length. The tenacity of 
silver is very great. A wire .078 of an inch 
in diameter, will support a weight of one 
hundred and eighty-seven pounds avoirdu- 
pois. Silver is a good conductor of calo- 
ric. Its expansive power is less than that 
of lead and tin, and greater than that of 
iron. When it is exposed to a white heat 
it melts. The temperature necessary to 
bring it to fusion has been calcidated at 
the 1000° of Fahrenheit; bht, according to 
Kirwan, it requires a higher tempeiature 
than 28“ Wedgwood to melt it,'^ although 
at that temperature it continues in a state 
of fusion. When it is cooled slowly after 
fusion, it exhibits some marks of crystalli- 
zation. It assumes the form of four-sided 
pyramids, or of octahedrons. If the heat 
be increased after the silver is melted, it 
boils, and may be reduced to vapour. The 
surface of melted silver is so extremely 
brilliant, that it seems to throw out spaiks, 
which is called coruscation by the work- 
men. Silver is a good conductor of elec- 
tricity. It has no perceptible taste or 
smell. 
Silver is not altered by exposure to the 
air, although it is soon tarnished, which is 
owing, as Proust ascertained, to a thin 
covering of sulphuiet of silver, which is 
formed by sulphureous vapours to which it 
is exposed ; but when it is subjected to a 
strong heat for a long time, in an open ves- 
sel, it combines with the oxygen of the at- 
mosphere, and is converted into an oxide. 
In the experiments of Macquer, the oxyda- 
tion of silver was effected by exposing it 
for twenty times successively in a crucible, 
to the strong heat of a porcelain furnace. 
At last perceptible traces of oxidation were 
observed, and a vitreous matter of an olive 
colour was obtained. In other experiments 
silver being acted on by the heat of a burn- 
ing-glass, was covered with a white pow- 
der, which was afterwards converted into a 
crust of a green colour. Van Marum pass- 
ed electric shocks through silver wire, 
whicli was instantly reduced to a kind of 
powder, wdth a greenish white flame, aijd 
the oxide which w^as formed was dissipated 
in vapour. The oxide of silver, which is 
formed by these processes, is of a greenish 
or yellow colour. It is composed of about 
ten parts of oxygen, and ninety of silver. 
The oxide of silver is very easily reduced, 
for the affinity of oxygen for this metal is 
very feeble. It is decomposed by the 
