"In the progress of industry, commercial nations have found it convenient to coin several different metals into money; gold for larger payments, silver for purchases of moderate value, and copper, or some other coarse metal, for those of still smaller consideration, They have always, however, considered one of those metals as more peculiarly the measure of value than any of the other two; and this preference seems generally to have been given to the metal which they happen first to make use of as the instrument of commerce. Having once begun to use it as their standard, which they must have done when they had no other money, they have generally continued to do so even when the necessity was not the same. The Romans are said to have had nothing but copper money till within five years before the first Punic war (Pliny, lib. xxxiii. cap. 3), when they first began to coin silver. Copper, therefore, appears to have continued always the measure of value in that republic. At Rome all accounts appear to have been kept, and the value of all estates to have been computed, either in asses or in sestertii. The as was always the denomination of a copper coin. The word sestertius signifies two asses and a half. Though the sestertius, therefore, was originally a silver coin, its value was estimated in copper. At Rome, one who owed a great deal of money was said to have a great deal of other people's copper."