Royal Academy of Sciences of Paris. 163 



periods before the Christian era at which that coincidence took 

 place : 



Julian era. Years before Christ. Date of IstThot. Date of Summer Solstice. 



76 4790 December 4 August 1 



1429 3285 November 22 July 20 



2934 1780 November 11 July 9 



4439 275 October 31 June 27 



It is therefore to one of these four periods that the commence- 

 ment of the Egyptian mode of calculation must be attributed. The 

 last of the four may be excluded from our consideration, because the 

 researches of M. Champollion have proved incontestably that the 

 an mi* vagus of 365 days was used by the Egyptians previous to the 

 year 1600 before Christ. We have therefore only to examine the 

 probability attaching to the first three ; and for this purpose it is 

 important to remark that the Egyptians, in their mythological sys- 

 tem, considered the star Sirius as the power influencing the rising 

 of the waters of the Nile ; and therefore it must be presumed that 

 their system commenced at a period when the heliacal rising of 

 Sirius coincided with the summer solstice, or rising of the Nile. 

 This occurred for the first time in the year 3285 B.C., previous to 

 which the rising of Sirius was more and more removed from the 

 summer solstice; the date of 4790 B.C. may therefore be also put 

 out of the question, and the doubt only remains between the years 

 3285 and 1780 B.C. The first, as we have before seen, coincides 

 precisely, and therefore furnishes a fair presumption that the Egyp- 

 tians at that period formed their year of 365 days ; but we cannot 

 be quite certain of the facts, because, supposing the addition of the 

 five days not to have been made until 1780, and consequently cal- 

 culating backwards by years of 360 days, we should only make a 

 difference of six Julian years, placing the period of coincidence 

 between the summer solstice and the 1st day of Paschous (the ninth 

 month) in the year 3291, when the heliacal rising of Sirius differed 

 only a day and a half from the summer solstice an error which 

 may easily be committed in determining the heliacal rising of a star 

 from observation only. 



From these observations, we arrive at the following important 

 conclusions: 1st. That the Egyptians, knowing that the cycle of 

 variation between the solar year and the annus vagus consisted of 

 1506 years, could always tell, by observing the number of days 

 which the 1st of the 9th month (Paschous) varied from the summer 

 solstice, in what year of the cycle they were ; and that at the time 

 of the alteration of the year by Augustus they could not be in more 

 than the third, and perhaps only in the second of such cycles from 

 the time of their first calculating in that manner. 2nd. That as all 

 the data on which this calculation of the year is founded relate to the 

 phases of the Nile, it is evident that it is of Egyptian, and not of 

 Chaldaic origin. 3rd. That as the phenomena relating to the Nile 

 continue at the present moment to occur in precisely the same 

 manner and at the same intervals as at the commencement of the 



Mi 



