CHRONOLOGY. 



405 



maiical. 



Chronolo- quence of this arrangement, it necessarily happened, that 

 gy, Mailie- eac h Jay of the week was marked by the name of the 

 planet which it now bears. In order to understand this, 

 the order of the planets must be given upon the Ptole- 

 maic system. Thus, 



1. Saturn. 4. Sun. 6. Mercury. 



2. Jupiter. 5. Venus. 7- Moon. 



3. Mars. 



As the day was divided into 24 hours, and as every 

 hour was called after one of the planets in their order, 

 the planets would be numbered three times in the first 

 day, and the three first planets four times. Thus, 



Origin of 



7+7+7+3 



Therefore the fourth planet, or the 

 the mrnea gun, will belong to the first hour of 

 ys of the 8econd da r' and wil1 consequently 

 he week, be the name of that day. 



During the second day, we have 

 From which it follows that the se- 

 venth planet, or the Moon, will com- 

 mence the third day. 



D uring the third day, we have. 



Hence the 3d planet, or Mars, will 



mark the first hour of the fourth day. 



During the fourth day, we have 



Hence the 6th planet, or Mercury, 



willdesignate the 1 st hourof the 5th day 



During the fifth day, we have . 



Hence the 2d planet, or Jupiter, 



will mark the first hour of the 6th day. 



During the 6th day we have .. 

 Hence the 5th planet, or Venus, 

 will mark the 1st hour of the 7th day. 

 During the seventh day, we have 



Consequently the first planet, or Saturn, will mark the 

 1st hour of the eighth day, and so on with the rest, the 

 ame planets marking the same days of every weekly period. 

 Hence we have the following arrangement : 

 1st day of the week Saturday, or the day of Saturn. 

 2J ........... Sunday, ..... day of the Sun. 



3d ........... Monday, ..... day of the Moon. 



4th ........... Tuesday, ..... day of Mars. 



5th .......... Wednesday, ---- day of Mercury. 



6th .......... Thursday, ..... day of Jupiter. 



7th .......... Friday, ..... day of Venus. 



This order of the days, first adopted by the Chaldeans, 

 was preserved by the Mosaic law. The Christians, how- 

 ever, began their week on Sunday, and the Mahometans 

 on Friday. 



The denomination of the days of the week has also 

 been explained by the following diagram, in which the 

 (even planets are placed in their order round the circle. 



1 + 7 + 7 + 7 + 2 



5 + 7 + 7 + 5 



2 + 7 + 7 + 7 + 1 



6 + 7 + 7 + 4 



3 + 7 + 7 + 7 



At the mark T? , or Saturday, the line directs us to , 

 or Sunday, which again directs us to J) , or Monday, 

 then to $ , or Tuesday, from which we are led to 9 , or 



\V\dnesday, and from this to If , or Thursday, which Chronolo. 

 conducts us to $ , or Friday. gy Mathe- 



matical 



SECT. III. On the Year and the Reformation of the N "-V"-' 

 Calendar. 



The next and most important chronological period 

 indicated by the celestial motions is the year. 



The solar or tropical year, is that period which cor- Solar year, 

 responds to the sun's revolution in the ecliptic from any 

 equinox or solstice to the same again, and consists of 

 365 days 5 h 48' 54". 



The sidereal year, is that portion of time which cor- sidereal 

 responds to the revolution of the sun from any fixed star year. 

 to the same star again, and is equal to 365 days 6 h 9' 15", 

 or 20' 21" shorter than the solar year. 



The lunar year is equal to twelve revolutions of the Lunar year, 

 moon from the sun to the sun again, or from one con- 

 junction with the sun to the next conjunction. It con- 

 tains 354 days 8 h 48' 36", and is 10 days 21 h 0' 18" 

 shorter than the solar year. 



The civil year is that which is used for the purposes Civil year. 

 of civil life. 



In the earliest periods of society, the most barbarous 

 nations could not fail to observe a regular return of the 

 seasons ; and the necessity of providing against the incle- 

 mency of winter, or the burning heat of the summer sea- 

 son, must have compelled them to ascertain, in a rude 

 manner, the length of the year. The period in which 

 the seasons returned would probably be measured at first 

 by the motions of the moon, and be reckoned equivalent to 

 12 of her monthly revolutions. Hence a year of 12 luna- 

 tions would be formed, each of which consisted of 30 days, 

 forming the lunisolar year of 360 days. This form of 

 the year was adopted by the Chaldeans, Egyptians, and 

 Indians, and was in use among almost all the nations of 

 antiquity. As the true solar year, however, of 365 days 

 5" 48' 54" exceeded the lunisolar year by about 5^ days, 

 the seasons would rapidly deviate from the months to 

 which they at first corresponded, and in the short space 

 of 34 years, the winter would happen in those months 

 which formerly corresponded with the summer season. 

 This enormous aberration was observed by almost all 

 nations, and was corrected by the addition of a few in- 

 tercalary days at certain intervals. By this means, in- 

 dependent of astronomical observation, the length of the 

 solar year would soon be found to consist of 365 days. 

 The Egyptians were very early acquainted with the year 

 of 3()5days. The Theban priests ascribed the invention of 

 it to Mercury or Thoth; and it seems to have been known 

 in the 12th or 13th century before the Christian sera. 



As the inundation of the Nile was annually announced Canicular 

 by the heliacal rising of Sirius, which was made to cor- year, 

 respond with the beginning of the year, it was soon dis- 

 covered that the heliacal rising of this star advanced 

 nearly one day in four years, and that in the space of 

 1461 years it would complete a whole revolution till it 

 again happened on the day originally fixed for the com- 

 mencement of the year. This period, which was equal 

 to 1460 Julian years, waa called the Great Egyptian or 

 Canicular Year. 



It is impossible to ascertain the time when the true Rcforma. 

 solar year was discovered. The Theban priests lay claim tio " of the 

 to the discovery, and the knowledge of it is said to have calendar - 

 been introduced into Greece by Plato and Eudoxus, 

 who obtained it as a secret from the Egyptians ; but at 

 whatever time this knowledge was obtained, it does not 

 appear to have been employed for the purpose of adjust- 

 ing the civil with the solar year, till the time of Numa 

 Pompilius. 



Romulus divided the year into 10 months or 304 days, 



