170 



Jamshid. In Egypt, the commencement of the year was 

 fixed at the time when the inundation of the Nile had 

 sufficiently abated to allow the operations of agriculture to 

 commence ; and it was observed in the first instance rudely, 

 by a nilometer, but afterwards with greater accuracy by a 

 gnomon : the first day of the year being the first day in 

 which the meridian shadow of an object had attained to a 

 standard length ; which standard length appears from cal- 

 culation to have corresponded with a south declination of 

 about 12}°. The solar year, intervening between the suc- 

 cessive occurrences of this phenomenon, was greater than 

 the mean tropical year, on account of the changes in the 

 equation of the sun's centre, and in the obliquity of the 

 ecliptic; and is shewn to have been about 1767 B.C., 

 neglecting the perturbations caused by the moon and planets, 

 365,243246, differing little from 365,2433 . . . which would be 

 its length, if the phenomenon gained a fifth part of a year, 

 in 300 years of 365 days. The Egyptians, observing this 

 equality, and being dissatisfied with the year that they for- 

 merly used, on account of the 366th day, which, occurring 

 in every fourth or fifth year, disordered their calendar, 

 resolved that with the next cycle they would limit the year 

 to 365 days, allowing no more intercalations. This change 

 they accordingly made, on the 8th Nov. 1767, from which date 

 they commenced not only a new lunisolar cycle of 600 solar 

 years, that is 600f years of 365 days, but also a cycle of the 

 seasons, consisting of 1500 solar years, or 1501 years of 365 

 days. The recurrence of either of these cycles was celebrated 

 as the return of a phoenix ; and those mentioned by Tacitus, 

 as having occurred under Sesostris, Amasis, Ptolemy Philadel- 

 phus, and Tiberius, are fixed in the autumns of the proleptic 

 Julian years, 1167, 567 and 267 B. C, and A. D. 34. The 

 date thus assigned for the reign of Sesostris agrees with that 

 which Mr. Cullimore has deduced from the astronomical 

 sculptures on the memnonium. The great period of 3000 



