The principal Roman coins were the as, of copper; the sestertius, quinarius, denarius, of silver; and the aureus, of gold.
1. The as, the unit of the Roman currency, contained originally a pound of copper, but it was diminished from time to time till at last it contained only 1/24 of a pound.
Note.--An as, whatever its weight, was divided into twelve unciae.
2. The sestertius contained originally 2 1/2 asses, the quinarius 5, and the denarius 10; but as the as depreciated in value, the number of asses in these coins was increased.
3. The as is also used as a general unit of measure. Thus--
Computation of Money
1. In all sums of money the common unit of computation was the sestertius, also called nummus; but four special points deserve notice:
In the examples under d), sestertium is treated as a neuter noun in the singular, though originally it was probably the genitive plural of sestertius, and the full expression for 1,000,000 sesterces was decies centena milia sestertium. The words centena milia were afterward generally omitted, and finally sestertium lost its force as a genitive plural, and became a neuter noun in the singular, capable of declension.
2. Sometimes sestertium is omitted, leaving only the numeral adverb: as, decies = 1,000,000 sesterces.
3. The sign HS is often used for sestertii, and sometimes for sestertia, or sestertium:
Weights and Measures
The following weights and measures deserve mention:
1. The Libra, also called As or Pondo, equal to about 11 1/2 ounces, is the basis of Roman weights.
2. The Modius, equal to about a peck, is the basis of dry measure.
3. The Amphora, containing a Roman cubic foot, equivalent to about seven gallons, is a convenient basis of liquid measure.
4. The Roman Pes or Foot, equivalent to about 11.6 inches, is the basis of long measure.
Note.-- Cubitus is equivalent to 1 1/2 Roman feet, passus to 5, and stadium to 625.
5. The Jugerum, containing 28,800 Roman square feet, equivalent to about six tenths of an acre, is the basis of square measure.