118 THE GREEK ASTRONOMY. 



.tional day at the end of February every fourth or leap year, is an ex- 

 ample of the principle of intercalation, by which the correction 

 was most commonly made. Methods of intercalation for the same 

 purpose were found to exist in the new world. The Mexicans added 

 13 days at the end of ever} 7 52 years. The method of the Greeks was 

 more complex (by means of the octa&teris or cycle of 8 years) ; but 

 it had the additional object of accommodating itself to the motions of 

 the moon, and therefore must be treated of hereafter. The Egyptians, 

 on the other hand, knowingly permitted their civil year to wander, at 

 least so far as their religious observances were concerned. " They do 

 not wish," says Geminus, 15 " the same sacrifices of the gods to be made 

 perpetually at the same time of the year, but that they should go 

 through all the seasons, so that the same feast may happen in summer 

 and winter, in spring and autumn." The period in which any festival 

 would thus pass through all the seasons of the year is 1461 years; for 

 1460 years of 365J days are equal to 1461 years of 365 days. This 

 period of 1461 years is called the Sothic Period, from Sothis, the name 

 of the Dog-star, by which their fixed year was determined ; and for 

 the same reason it is called the Canicular Period. 16 



Other nations did not regulate their civil year by intercalation at 

 short intervals, but rectified it by a reform when this became neces- 

 sary. The Persians are said to have added a month of 30 days every 

 120 years. The Roman calendar, at first very rude in its structure, 

 was reformed by Numa, and was directed to be kept in order by the 

 perpetual interposition of the augurs. This, however, was, from vari- 

 ous causes, not properly done ; and the consequence was, that the 

 reckoning fell into utter disorder, in which state it was found by Julius 

 Csesar, when he became dictator. By the advice of Sosigenes, he 

 adopted the mode of intercalation of one day in 4 years, which we still 

 retain ; and in order to correct the derangement which had already 

 been produced, he added 90 days to a year of the usual length, which 

 thus became what was called the year of confusion. The Julian Cal- 

 endar, thus reformed, came into use, January 1, B. c. 45. 



Sect. 4. 'Attempts at the Fixation of the Month. 



THE cii-cle of changes through which the moon passes in about 

 thirty days, is marked, in the earliest stages of language, by a word 

 which implies the space of time which one such circle occupies; just 



Uranol. p. S3. 16 Ccnsorinus de Die NataU, c. IS 



