It is very possible that the market, given free rein, might eventually establish one single metal as money. But in recent centuries, silver stubbornly remained to challenge gold. It is not necessary, however, for the government to step in and save the market from its own folly in maintaining two moneys. Silver remained in circulation precisely because it was convenient (for small change, for example). Silver and gold could easily circulate side by side, and have done so in the past. The relative supplies of and demands for the two metals will determine the exchange rate between the two, and this rate, like any other price, will continually fluctuate in response to these changing forces. At one time, for example, silver and gold ounces might exchange at 16:1, another time at 15:1, etc. Which metal will serve as a unit of account depends on the concrete circumstances of the market. If gold is the money of account, then most transactions will be reckoned in gold ounces, and silver ounces will exchange at a freely-fluctuating price in terms of the gold.
— Murray Rothbard; What Has Government Done to Our Money?
