Elementary arithmetic, with brief notices of its history... by Robert Potts.

ON THE DIVISIONS AND MEASURES OF TIME.

11

In the early ages of the Grecian States, the traditions which the
settlers brought with them appear to have been of the most primitive
character. Their years were divided into seed time and harvest, and
their days into the times of labour and rest. The time from sunrise
to sunset was divided into three parts, the morning, midday, and
evening. In the age of Homer, lunar months were in use among
them (Odys. xiv. 162), and the Athenian year was reckoned by the
periods of the moon, and it was long after this time before any
attempts were made to adjust the motions of the moon and the sun.
The traditional accounts extant of the sages of Greece in their travels
in search of wisdom, about 600 B.c., clearly show that scientific knowledge had not then begun to be cultivated in Greece. Thales of
Miletus, and Solon, his contemporary, both visited Egypt as the chief
school of knowledge in their time. Herodotus has recorded (i. 74)
that Thales foretold to the Ionians an eclipse of the sun, which has
been determined to have taken place in the year 585 B.c. Thales
taught that a revolution of the moon did not exceed thirty days, and
assigned the year to consist of twelve months of thirty days each.
This he probably learned in Egypt. Herodotus (ii. 3, 4) writes that
he himself acquired much information from the priests at Memphis,
and that he went to Thebes, and to Heliopolis, the great seat of
learning, expressly to try whether the priests of these places agreed
in their accounts with the priests of Memphis.
Solon found the adjustment of the year by Thales was erroneous,
and settled the twelve months of the year to consist of twenty-nine
and of thirty days alternately. This method made the year to consist
of 354 days. Both Thales and Solon devised different modes of
adjusting the motions of the sun and the moon, but neither of them
appears to have been successful.l
Mleton was an astronomer of Athens at the time of the Peloponnesian war, and refused to sail with the expedition to Sicily, foreseeing
the calamities that were likely to follow that rash enterprise. He
had observed that the motion of the moon fell short of the motion of
the sun by some hours every year, and this difference, scarcely perceivable in a small number of years, he foresaw would, in the course
of a long period of years, entirely invert the reckoning of the seasons,
and it would be found that the season of summer would really happen
in winter, and the season of spring in the autumn. He succeeded in
his attempts to adjust the motions of the sun and of the moon more
accurately than before, and maintained that the lunar year and the
solar year could begin at the same time, or that the sun and the moon
could begin to move from the same point in the heavens. He calculated that when the sun had finished nineteen periods of its yearly
motion, and the moon 235 of its monthly periods, both the sun and
the moon would return nearly to the same position in the heavens in
which they had been nineteen years before; or, in other words, after
1 The year of the ancient Greeks was luni-solar, consisting of 12 months of
30 days, each day half daylight and half darkness, as is clear from several testimonies, and is represented by the riddle of Cleobulus:ETs 6,ra7r4ip, Trates 5e Sv6aEIcKa' rTiv e bcK4d0r
na^iSes TpLICKOCVTa, icdv&LXa eGos Exovo-ai
At lev AevKcai aotlyv ESY, a16' avre TeAatEvat'
'AOaaro be'E re oeo'ai, airo(pOivvOove7ir a 7 raoai.