An enormous amount is used in the manufacture of jewelry, most of which is used over and over again. By far the greater part, however, is used as a commercial medium of exchange--that is, as coin. For this purpose its employment is wellnigh universal; and indeed this has been its chief use since the beginning of written history. Gold coin of the United States is 900 fine, that is, 900 parts of every thousand is pure gold; gold coin of Great Britain is 916-2/3 fine. In each case a small amount of silver, or silver and copper, is added to give the coin the requisite hardness. The coining of gold, and also other metals, is a government monopoly in every civilized country. The fiat value of gold throughout the commercial world is the equivalent of $20.6718 per troy ounce of fine metal; an eagle weighs, therefore, 2580 grains. The real value, however, is reckoned by a different and a more accurate standard, namely, the labor of man, and this, the sporadic finds of placer gold excepted, has not changed much in two thousand years or more. The increased production has scarcely equalled the demand for the metal; moreover, the longer a mine is worked the greater becomes the expense of its operation. Improved processes for the extraction of gold have not created any surplus of gold; indeed, the supply is not equal to the demand; and this fact keeps the metal practically at a fixed value. =Silver.=--Silver is about as widely diffused as is gold, but it is more plentiful. It is found sparingly in most of the older rocks and also in sea-water. It was used by the Greeks for coinage more than eight hundred years before the Christian era, and was known to the Jewish people in very early times. According to the writer of the Book of Kings (1 Kings x. 21), "It was nothing accounted of in the days of Solomon," but Tacitus declares that in ancient Germany silver was even more valuable than gold. The mines of Laureion (Laurium) gave the Greek state of Attica its chief power, and the failure of the mines marked the beginning of Athenian decline. Silver 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.