80 LENGTH OF THE CIVIL YEAR. SECT. XII. 



it is nearly equal to a revolution of the sun, so that the 

 addition of a supernumerary day every fourth year 

 nearly compensates the difference. But in process of 

 time further correction will be necessary, because the 

 fraction is less than the fourth of a day. In fact, if a 

 bissextile be suppressed at the end of three out of four 

 centuries, the year so determined will only exceed the 

 true year by an extremely small fraction of a day ; and 

 if in addition to this a bissextile be suppressed every 

 4000 years, the length of the year will be nearly equal 

 to that given by observation. Were the fraction neg- 

 lected, the beginning of the year would precede that of 

 the tropical year, so that it would retrograde through 

 the different seasons in a period of about 1507 years. 

 The Egyptian year began with the heliacal rising of 

 Sirius, and contained only 365 days, by which they lost 

 one year in every 1461 years, their Sothaic period, or that 

 cycle in which the heliacal rising of Sirius passes through 

 the whole year and takes place again on the same day. 

 The commencement of that cycle is placed by ancient 

 chronologists in the year 1322 before the Christian era. 

 The division of the year into months is very old and almost 

 universal. But the period of seven days, by far the 

 most permanent division of time, and the most ancient 

 monument of astronomical knowledge, was used by the 

 Brahmins in India with the same denominations em- 

 ployed by us, and was alike found in the calendars of the 

 Jews, Egyptians, Arabs, and Assyrians. It has survived 

 the fall of empires, and has existed among all successive 

 generations, a proof of their common origin. 



The day of the new moon immediately following the 

 winter solstice in the 707th year of Rome, was made the 

 1st of January of the first year of Julius Caesar. The 

 25th of December of his forty-fifth year is considered as 

 the date of Christ's nativity ; and the forty-sixth year of 

 the Julian Calendar is assumed to be the first of our 

 era. The preceding year is called the first year before 

 Christ by chronologists, but by astronomers it is called 

 the year 0. The astronomical year begins on the 31st 

 of December at noon ; and the date of an observation 

 expresses the days and hours which have actually elapsed 

 since that time. 



