162 Science
The Bedawiyyin of the Sahara still call it Er-Rigl—'the leg*.
Other constellations which can be identified axe Bootes (crocodile
and hippopotamus); Cygnus (a man with outstretched arms)
which played an important part in Egyptian cosmology; Orion
(represented as a man running and looking backwards over his
shoulder); Cassiopeia (a figure with arms extended); Draco and
possibly the Pleiades; Scorpio and Aries. Sirius was 'The Great
Star'. An early myth regarding Thoth and the injured eye of
the sun-god may point to an underlying conception of the
part played by the moon in eclipses. Particular sanctity was
attached to the circumpolar stars, visible throughout the year—
'the never vanishing ones', 'the imperishable stars5.
The twelve zodiacal signs are entirely absent from the sacred
astronomy of Egypt before the Greek period. Instead, the
'dekans' were used to divide the year. These are groups of
stars, or a conspicuous star, rising at particular 'hours of the
night' during the 36 successive periods of 10 days each, con-
stituting the year. They are situated within a wide equatorial
belt and commence with Sirius ('the mistress of the year').
Some of the names survive in Greek.
Each period of 10 days was marked by the heliacal rising of
the next dekan on the eastern horizon. Lists of dekans were
prepared for ascertaining the time of the night if the calendar
date was known, or for determining the dekan, if the hour of
the night was known. Dekan calendars in a much debased form
and full of copyist's errors appear on the lids of Eleventh-
Dynasty coffins (c. 2100 B.C.).
The 36 dekans form the old year of 360 days, ignoring the five
additional or epagomenal days. They therefore fell at different
periods in successive years. The tables give the days and months
on which a dusk culmination, a dusk setting or a dawn rising of
the corresponding dekanal constellation occurred. They could
therefore be used to fix the day and season and the hour of the
night by anyone who observed the positions of the constellations
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