SESTEILTTUS, a lloman coin, which originally consisted of 24 aces, as the name implies, uestertine being a contraction of semis tertina, the third a-half, which is the Roman way of expressing two and a-half. The sestertius belonged both to the brass and silver coinage; and in both it was of the same value, namely, one-fourth of the denarius. This value agreed with its value in aces so long as the denarius consisted of 10 uses. But at an early period the as was reduced in value, and 16 aces made equal to the denarius [As], and then the sestertius, its value with reference to the denarius remaining the same, became of course equal to 4 rises. On Mr. Hussey 's compu tation the value of the denarius after the reduction was 84d., and therefore the sestertius was •worth 2p/. After the time of Augustus the denarius was reduced to the eighth of an ounce, and was worth 74d., and therefore the seetertius was worth 1:d. The sestertius of the brass coinage was made of the same metal as the as.
The Romans generally reckoned sums of money in sestertii, although the coin used in making payments was commonly the denarius. Large sums they reckoned by sesterlia, that is, sums of a thousand sedan!. It is very important to attend to the phrases used in such computa tions. The coin itself was called sestertius, or a'skertiva mamma, or simply nummus. The sum of a thousand sestertii was expressed by or M. matertium, or 31. nummi, or M. minimum, or sum morum, or M. aesterlii nummi, or M. sestertium minimum. The singular lestertium is never used for a thousand eestertii, but the plural sestertia is used for all multiples of a thousand sestertii, up to a thousand ; sometimes the word Heillio (thousands) is used instead of materna ; sometimes neither word is expressed ; and sometimes nummunt is added. Thus 600,000 sestertii, or 600 sestertia, might be expressed by any of the following phrases : eacenta materna, sementa millie, &ricotta alone, or seseenta materna uumnaint. Sums of 1000 seatertia and upwards were expressed by the numeral adverbs with the termination ies, which i implies that the number to which it affixed is to be multiplied by 100. Thus deeies, undeeies, duodeeies, ricks tricies, tricks quinquies, stand respectively for 1000, 1100, 1200, 2000, 3000, 3500 eestertia.
These forms are, however, sometimes varied. Thus Cicero (` in Verr.,' ii. 1, 39) uses quaterdeeies for 1400, and decies el octingenta millia for 1800 sestertia. When two such adverbs come together, if the larger is first, they must be added together ; but if the smaller is first, they must be multiplied. Thus we have in a passage of Suctonius (` Aug.,' 101), wage, et eixima(ioties for 150,000 andertia, and immediately after aslant. cwatenlecies willies for 1,400,000 ftestertia. (In the latter cane, care must be taken not to reckon the termination if, twice over in multiplying; it is not ]400x 100,000, but 1000x 100.) The symbol 115 or 11S is often used both for sestcrtii and for sestertia. It stands for litre fibre semis (two pounds and a-half). When applied to ststertii its meaning is clear enough, since the as was originally a pound (litre) of brass. When applied to sestertia it meant, according to Gronovius (' Pee. Vet.; I. 4, 11), two pounds and a-half of 'silver, which lie calculates to have been originally equal to 1000 riestertii, and therefore to have represented that value ever after. It is often difficult to determine whether the symbol IIS stands for ststertii or ststertia. When the numeral is written in cipher, and piss a line over it, it stands for the adverb in ire, and the HS means wstertia: thus, 11S. is avedriagestier, or forty thousand sestertia. Some timed the numeral is found with the singular of sestertixin, as sesterlii decks, or scstert;o decks. Gronovius explain.' these forms, and also the use of sestcrtinin with the adverb in is (which he considers to be, in this case, an accusative singular), by understanding with them the wont powlas, a pound (of silver), according to which sestcrtium in these forms means two pounds and a-half of silver, or 1000 sestertii. Hence, if those forms are used with is numeral in cipher, they mean the number of sestertia represented by the adverb in ics of that numeraL Thus sestertio X is decks or 1000 sestertia.
According to the value given above for the seatertius, the sestertiunt was worth SI. 17s. Id.
The word &Werth(/' is often used indefinitely for any very small sum. (Hussey,' On the Ancient Weights and Money,' c. x., § 1, 3, 6.)