This monetary system is very unstable: due to the fluctuation of the commercial value of the metals, the metal with a commercial value higher than the currency value tends to be used as metal and is withdrawn from circulation as money (Gresham's Law).
In the United States, toward the end of the nineteenth century, bimetallism became a center of political conflict. Bimetallism and "free silver" were favored by Democrats, populists, and Western states with silver mines. Had it become law, it would have tipped the balance of economic power away from established financial interest on the East coast and toward the newer states in the West. William Jennings Bryan, the eloquent champion of the cause, gave a famous speech at the National Democratic Convention on July 9, 1896 asserting that "The gold standard has slain tens of thousands. He referred to "a struggle between 'the idle holders of idle capital' and 'the struggling masses, who produce the wealth and pay the taxes of the country;' and, my friends, the question we are to decide is: Upon which side will the Democratic party fight?" At the peroration, he said "You shall not press down upon the brow of labor this crown of thorns, you shall not crucify mankind upon a cross of gold."