A HISTORY OF SCIENCE 



later, in our own time, Sir Joseph Norman Lockyer, fol- 

 lowing up the work of various intermediary observers, 

 has given the subject much attention, making it the 

 central theme of his work on The Dawn of Astronomy. 1 

 Lockyer 's researches make it clear that in the main the 

 temples of Egypt were oriented with reference to the 

 point at which the sun rises on the day of the summer 

 solstice. The time of the solstice had peculiar in- 

 terest for the Egyptians, because it corresponded 

 rather closely with the time of the rising of the Nile. 

 The floods of that river appear with very great regu- 

 larity; the on-rushing tide reaches the region of Heli- 

 opolis and Memphis almost precisely on the day of the 

 summer solstice. The time varies at different stages 

 of the river's course, but as the civilization of the early 

 dynasties centred at Memphis, observations made at 

 this place had widest vogue. 



Considering the all-essential character of the Nile 

 floods without which civilization would be impossi- 

 ble in Egypt it is not strange that the time of their 

 appearance should be taken as marking the beginning 

 of a new year. The fact that their coming coincides 

 with the solstice makes such a division of the calendar 

 perfectly natural. In point of fact, from the earliest 

 periods of which records have come down to us, the 

 new year of the Egyptians dates from the summer 

 solstice. It is certain that from the earliest historical 

 periods the Egyptians were aware of the approximate 

 length of the year. It would be strange were it other- 

 wise, considering the ease with which a record of days 

 could be kept from Nile flood to Nile flood, or from 

 solstice to solstice. But this, of course, applies only 



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