762 THE POPULAR SCIENCE MONTHLY. 



rected the error, after many other devices, by intercalating three 

 months every eight years, making every eighth year consist of fifteen 

 months a method used by them for many years, perhaps centuries. 

 It is said, however, that the length of the year was known, as early as 

 the time of Solon, to be three hundred and sixty-five and one quarter 

 days. Prior to the time of Numa, the Roman year consisted of ten 

 months. He divided it into twelve lunar months, and to correct the 

 error of eleven days a month was intercalated every second year. The 

 management of this matter was intrusted to the priests, who added 

 days whenever they deemed them necessary. But, owing to their 

 ignorance of astronomy, this method proved irregular and erroneous, 

 and the winter months were gradually carried back into autumn, the 

 autumn months into summer, etc. 



These errors had become so troublesome in the time of Julius Csesar 

 that he undertook, with the aid of an eminent astronomer (Sosigenes), 

 to correct the calendar, which was done as follows : The Roman civil 

 year had lost about ninety days. These were added to the year of 

 three hundred and fifty-five days, making that year consist of four 

 hundred and forty-five days, which is known in history as the " year 

 of confusion." The year henceforward was made to consist of three 

 hundred and sixty-five days, by adding ten days distributively to as 

 many months. The odd quarter of a day was not noted until every 

 fourth year, when the sum of these fourths made one day, and that 

 year consisted of three hundred and sixty-six days. This odd day 

 M^as inserted after the sixth day before the kalends of March, i. e., after 

 the 24th of February, and was not counted as an addition to the year, 

 but as a sort of appendix. Hence the sixth of the kalends of March 

 was called bissextus, or double sixth, which root is still retained in our 

 word bissextile, though the day is now added at the end of February. 

 This arrangement would have been entirely correct had the year con- 

 sisted of exactly three hundred and sixty-five and one quarter days. 

 It was, however, in course of time, discovered to be erroneous, and an- 

 other correction was made, which we will consider by and by. This 

 new system went into effect on January 1, 46 b. c. 



The subdivisions of the Roman month were apparently arbitrary. 

 The days were not numbered as we have them, but the first day of 

 every month was called the calends, the fifth the nones, and the thir- 

 teenth the ides, except in the months of March, May, July, and Octo- 

 ber, when the nones fell on the seventh and the ides on the fifteenth. 

 From these points the days were counted backward i. e., the last of 

 February was called Prid., Kal., Mar., etc. 



Names of Months. The division of days into weeks was invented 

 at a very early day by the Chaldeans, and was afterward adopted by 

 almost all civilized nations, and by the Romans about the third century 

 A. c. The principle upon which the days were named is odd enough 

 to deserve especial notice. The order of the planets, according to the 



