crescent lying on its back and two stars near it.
They are seen very distinctly at the top of the photograph of the
boundary-stone from the Louvre, given on p. 318, and also immediately
above the head of the Sun-god in the photograph of the tablet from
Sippar, on p. 322. Their significance is now clear. Four thousand years
before the Christian era, the two Twin stars, Castor and Pollux, served
as indicators of the first new moon of the year, just as Capella did two
thousand years later. The "triad of stars," then, is simply a picture of
what men saw, year after year, in the sunset sky at the beginning of the
first month, six thousand years ago. It is the earliest record of an
astronomical observation that has come down to us.

[Illustration: WORSHIP OF THE SUN-GOD AT SIPPARA.]

How simple and easy the observation was, and how distinctly the year was
marked off by it! The month was marked off by the first sight of the new
thin crescent in the evening sky. The day was marked off by the return
of darkness, the evening hour in which, month by month, the new moon was
first observed; so that "the evening and the morning were the first
day." The year was marked off by the new moon being seen in the evening
with a bright pair of stars, the stars we still know as the "Twins;" and
the length of the year was shown by the evening of the month, when moon
and stars came together. If on the first evening, it was a year of
twelve months; if on the third, one of thirteen. There was a time when
these three observations constituted the whole of primitive astronomy.

In later days the original meaning of the "Triad of Stars" would seem to
have been forgotten, and they were taken as representing Sin, Samas, and
Istar;--the Moon, the Sun and the planet Venus. Yet now and again a hint
of the part they once played in determining the length of the year is
preserved. Thus, on the tablet now in the British Museum, and shown on
p. 322, sculptured with a scene representing the worship of the Sun-god
in the temple of Sippar, these three symbols are shown with the
explanatory inscription:--

"The Moon-god, the Sun-god, and Istar, dwellers in the abyss,
Announce to the years what they are to expect;"

possibly an astrological formula, but it may well mean--"announce
whether the years should expect twelve or thirteen months."

As already pointed out, this method had one drawback; it gave a sidereal
year, not a tropical year, and this i