ilver is rarely found in a metallic state. For the greater part it
occurs combined with chlorine ("horn silver"), or with sulphur ("silver
glance"), or in combination with antimony and sulphur ("ruby ore"). The
ranges of the western highland region of the American continent yield
most of the present supply. The mines of Colorado, Montana, Utah, and
Idaho produce about six-sevenths of the yield in the United States,
which in 1900 was 74,500,000 ounces. In Europe the Hartz Mountains have
been famous for silver for several centuries.

About four-fifths of the silver bullion is used in the arts, most of it
being manufactured into ornaments or into table-service called "plate."
A considerable amount is used in photography, certain silver salts,
especially the chloride and the bromide, changing color by exposure to
the light. The remaining part of the silver output is made into coin.

The ratio of silver and gold has fluctuated much in the history of
civilization. In the United States the value of an ounce of fine silver
is fixed at $1.2929, thereby making the ratio 16 to 1. The silver
dollars, 900 fine, were coined on this basis, weighing 412.5 grains.
With the tremendous output of the silver mines between 1870 and 1880 the
price of silver fell to such an extent that, in time, most countries
limited the amount of coinage or demonetized it altogether. In the
United States the purchase of silver bullion for coinage has been
practically suspended, and the silver purchased is bought at the bullion
value--about fifty cents per troy ounce in 1900. In Japan the ratio has
been officially fixed at 32 to 1.

=Copper.=--Copper is probably the oldest metal known that has been used in
making tools. An alloy of copper and tin, hard enough to cut and dress
stone, succeeded the use of flint and jade, and its employment became so
general as to give the name "bronze" to the age following that
characterized by the use of stone implements.

Copper is very widely distributed. It occurs in quantities that pay for
mining in pretty nearly every country in the world. The rise of Egypt as
a commercial power was due to the fact that the Egyptians controlled the
world's trade in that metal, and it is highly probable that the
conquests of Cyprus at various times were chiefly for the possession of
the copper mines of Mount Olympus.

At the present time there are several great centres of production which
yield most of the metal used. These are the Roc