Science 165 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. Mathematics 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.