"The Nemean and Isthmian [games in ancient. Greece] were
celebrated each twice in every Olympiad, at different seasons
of the year: the former in the plain of Nemea, in Argolis,
under the presidency of Argos; the latter in the Corinthian
isthmus, under the presidency of Corinth. These, like the
Pythian and Olympic games, claimed a very high antiquity,
though the form in which they were finally established was of
late institution; and it is highly probable that they were
really suggested by the tradition of ancient festivals, which
had served to cement an Amphictyonic confederacy."
_C. Thirlwall,
History of Greece,
chapter 10._