220 NATURAL HISTORY OF PRECIOUS METALS, &c.
and
Triples of these are also extant, but the whole series ranks amongst
the rarest of the rare. In fact, the republican gold currency was
almost as restricted in extent as that of Athens. But in the last
half-century of the Eepublic it was considerably augmented, Julius
Caesar, and the heads of the opposite party (more particularly in the
Civil Wars following his death), coining pretty largely gold didrachms
of the weight of the gold Philippus, then the universal currency of the
civilised world. But under the Empire the whole monetary system was
changed : gold became the standard, a matter of necessity in a
condition of wealth (as it had been before under the Persian Empire) ;
silver was only issued to the amount required for necessary small
change, and by some of the first Caesars hardly at all, e. gr., in
the reigns between Tiberius and Vespasian. Of some of these emperors,
as Claudius and Nero, more gold pieces than silver are actually now
extant. Under the latter the issue of gold and bronze, beautiful pieces
in point of execution, was enormous,* yet his denarii are most
carelessly made and rare ; of Claudius one may venture to say no
genuine silver exists ; all now seen in cabinets being plated pieces,
and due to ancient forgers, or if in solid silver to their modern
brethren.
Gold therefore being now the standard, the taxes were all estimated in that metal, eveiy caput being
assessed at so many aurei. Of this regulation certain tyrants took
advantage, like Heliogabalus, who, coining aurei of ten or more in
weight, even up to 100 (bilibres), exacted the same number of
aurei as before from the payer, whilst he decupled or centupled the
actual amount. Sev. Alexander, acting conversely upon the same
principle, retained
