462 Professor Renwick on 



The heliacal rising of Sirius is fixed by Censorinus as having 

 happened, in the year 139 A.D., on the 20th of July ; and the 

 truth of this statement is amply confirmed by astronomic calcu- 

 lation. Between this date and the 25th of June there intervene 

 twenty-four days, which is a difference that will take place 

 between the Julian and Gregorian calendars in 3200 years. 

 The observation cannot, therefore, be carried back farther than 

 3060 years before the Christian era ; and if made by simple 

 inspection of the river, instead of being referred to the marks 

 upon a Nilometer, may have occurred 200 or 300 years later, 

 particularly if made at This, instead of being observed at the 

 frontiers of Nubia. 



This is the first of the investigations by which I conceived 

 myself warranted in restricting the earliest settlement of a 

 colony in Egypt to about 2800 years before the Christian 

 era. 



II. The year of the Egyptians differed from that of any 

 nation of antiquity whose records or traditions have come down 

 to us, Herodotus informs us*, * That the Egyptians were the 

 first of men who invented the year, and divided it into twelve 

 months ; and this they found out by means of the stars. In 

 this they seem to have acted more prudently than the Greeks ;' 

 for the latter ' intercalated every third year, but the Egyptians 

 annually add five days to the twelve months of thirty days 

 each.' Diodorus Siculus gives us another form of the yearf: 

 * They say that they are the most ancient of nations ; and that 

 philosophy and astronomy were by them invented, the situation 

 of their country assisting them to ascertain more clearly the 

 rising and setting of the stars. The months and years are, 

 however, arranged by them in a peculiar manner : for adapt- 

 ing their days, not to the motion of the moon, but to that of 

 the sun, they attribute thirty days to each month, but after each 

 twelfth month they intercalate five days and a quarter ; and 

 thus complete the circle of the year.' 



This apparent discrepancy is explained by another ancient 

 author^ : * For they were desirous that the festivals of the 

 gods should not be represented always at the same season, but 

 they wished them to revolve through every period of the year ; 



* Lib. ii. cap. 4. t Lib. i. 



* Geminus, as quoted by Marsham and Witsius. 



