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watches in Arabia are altered daily at sunset to agree with the
time of sunset as shown by the almanack. The day begins at
sunset. (Cf. Gen. i. 13.)
Observations of the directions of shadows during the day time
as well as observations of the night sky enabled early observers
to acquire a sense of direction and to mark the meridian1
dividing the period of daylight conveniently into morning and
afternoon. The orientation of the faces of the Great Pyramid
to the cardinal points of the compass to a very high degree of
accuracy points to exact observations of transits of stars across
the meridian. There is no direct evidence that the Egyptians
determined the summer (or winter) solstice, when the sun
reaches its highest (lowest) point in the heavens, and its noon
shadow is shortest (longest): or the equinoxes, when the sun rises
due east and sets due west. It is difficult, however, to imagine
that these features passed unnoticed.
No records of continuous observations have yet been brought
to light. Should any be discovered in the future, it might be
possible to decide many points, at present matters of con-
jecture: such, for example, as to whether the shadows cast by
pyramids and obelisks were actually used to measure time.
Vexed questions of chronology might be settled if dated records
of celestial phenomena as, for instance, eclipses were available.
The sources of our knowledge of Egyptian mathematics are
meagre. The Greeks are commonly spoken of as the first
mathematicians, but that is only because a considerable amount
of literature on the subject has survived.
The Egyptians achieved astonishing results in the practical
applications of their knowledge, but no written records as to
1 An observer standing with his face to the north is in the plane of the
meridian. The sun crosses the meridian at the highest point of its daily
journey across the sky. It then casts the shortest shadow.