Historical studies

THE HELIACAL RISING OF SIRIUS
them, and has indicated the division of the Nile each stage. The details of the numbers and their
course into stages, with wayside shrines of Hapi at division will be found on pis. i, ii.
THE HELIACAL RISING OF SIRIUS.
14. The Length oftJuSothisFeriod. Much research
has been made into the origin of Egyptian chronology
and its connexion with the heliacal rising of Sirius,
but it was not until the publication by the late Professor
Oppolzer of his memoir " Ueber die Lange
des Siriusjahrs und der Sothisperiode," in the 90th
volume of the Sitzungsberichte of the Vienna
Academy, that the question was put upon a sound
basis. Starting with the well-determined observa-
tion of A.D. + 139, reported by Censorinus, Oppolzer
calculates the length of the Sirius year and thence
the Sirius period, which is the interval between two
successive Sothic risings coincident with the ist Thoth.
He shews that the Sirius period is of irregular length,
and gives the following series of Julian years as those
commencing Sothis periods :
—
Interval.
Sothis Period. Juli.in Years. Julian Years. Egyptian Years.
Zero period A.D. — 4235
1460 1461
1 .. -2775
1458 1459
2 ,. -1317
1456 1457
3 .. + 139
1452 1453
4 >. +1591
1448 1449
5 ., +3039
Recent discoveries necessitate the calculations
being carried further back, particularly for the pur-
pose of determining the seasonal changes in the
commencement of the Sothis period. Two periods
beyond Oppolzer's zero period have therefore been
computed by the formulae given on p. 577 of
his memoir. These are the years A.D. — 5705 and
— 7171. As Oppolzer designated the period commencing
A.D. — 423s by zero, the two more remote
epochs are called — i and — 2 periods.
By E. B. KXOBEL.