In addition there is also a non-interest-bearing debt of $389,407,800, of which $346,681,016 consists of treasury notes issued during the Civil War, and popularly known as "greenbacks" from their color. The national interest-bearing debt of the United States on June 30, 1921, amounted to about $24,000,000,000. The total debt of England is now about $40,000,000,000, that of France about $46,000,000,000, and that of Germany over $30,000,000,000. =The Monetary System.=--The coining of money is now regarded everywhere as a proper if not a necessary function of government. Under the Articles of Confederation, this power was possessed by the states as well as by Congress, though in fact it was exercised by neither. The framers of the Constitution decided that the most effective way of securing a uniform system of money would be to place the whole matter under the control of the national government, and so Congress alone was given the power of coinage. At the same time, remembering how the states had before 1789 flooded the country with paper money which in some instances had become worthless, the framers of the Constitution wisely decided to prohibit them from issuing bills of credit, that is, paper designed to circulate as money. Likewise they were forbidden to make anything but gold and silver coin a legal tender in the payment of debts. _The Acts of 1792 and 1834._--As soon as the new government under the Constitution had gone into operation, steps were taken to provide a system of metallic currency. In 1792, an act was passed providing for the establishment of a mint at Philadelphia and for the striking of both gold and silver coins.[38] The gold coins were to be the double eagle, the eagle, the half eagle, and the quarter eagle; the silver coins were to be the dollar, the half dollar, the quarter, the dime, and the half dime.[39] As the market value of a given quantity of gold bullion was then about fifteen times that of silver, the weight of the silver coins was made fifteen times that of the corresponding gold coins. But as the value of gold bullion presently began to increase in comparison with silver, it was necessary to readjust the ratio so as to keep both in circulation, and so in 1834 the weight of gold coins was reduced and the ratio made sixteen to one. [38] Later mints were established at Denver, San Francisco, and New Orleans. Assay offices for refining and determining the purity of bullion have been established at New York, St. Louis, Deadwood, Helena, Boise, Carson City, Salt Lake, Seattle, and Charlotte, North Carolina. To give strength and hardness to gold and silver coins an alloy of copper equal to one tenth of their weight is added. [39] In addition to the gold and silver coins mentioned above are the five cent piece (nickel) and the one cent piece (copper).