16 On the Magnilude of the Year. 



stance, have approximated to a still greater degree of exactiiessv 

 Tycho Brahe by tiiis method computed the solar tropical year 

 at 365 days, 5 hours, 49 minutes ; and the same measure was 

 found on examining two corresponding observations at IfiS years 

 distance; the one by Tycho Brahe at Uraniberg, A.D. 1585, 

 and the other l)v Dr. Bradley, at Greenwich, 1/53. 



Thehites, an Arabian astronomer, about the year of Christ 

 1200, computed the sidereal year at 365 days, 6 hours, 9 mi- 

 nutes, 12 seconds; an exactness confirmed by the most able 

 and accurate astronomers of late years, aided by the most superior 

 and perfect instruments fabricated by human hands. This mea- 

 sure very nearly agrees with that of the Indian astronomers, 

 computed at 365 days, G hours, 12 minutes, and 9 seconds ; see 

 Phil. Mag. vol. 55. p. 314. The Newtonian astronomy reckons 

 365 davs, 6 hours, 9 minutes. These are evident proofs of the 

 fact, that the sidereal vear is greater than the solar year, as at- 

 tested bv astronomers of different nations. 



It is generally I)elieved the Hebrews and Egyptians followed 

 the reckoning of the antediluvians in their years and months; 

 each month consisting of 30 days,and each year of twelve months 

 and five intercalary davs, in respect of the sun ; and therefore it 

 is that Hermes Trismegistus, the earliest of the Egyptian astro- 

 nomers, fixed the year at 365 days, which is tlie common quan- 

 tity in whole days; but this not being found to correspond with 

 the solar motions, Ennius, another astronomer of the same na- 

 tion, stated the full year of the sun at 366 days, which quantity 

 Deiiiocritus, who studied among the Chaldeans, CahppuS', 

 Archimedes, Geinius of Rhodes, and Sosigenes, who assisted 

 Julius Caesar in reforming the Roman calendar, also followed; 

 and hence we must consider the solar year to have been com- 

 puted in three several quantities, the common year 365 days, 

 the full year 366 days, and the mean or astronomical year at 365 

 days, 6 hours. 



The year of Oenepidus of Chios, computed at 365 days, 

 8 hours, 57 minutes; that of Harpalus, at 365 days, 13 hours ; 

 and that of Melon, rt 365 days, 6 hours, IS minutes, 56 seconds, 

 belongs to the stars, wherein Meton, the inventor of the lunar 

 cycle among the Greeks, came very near the truth. 



Hipparchus, the first among the ancients who discovered the 

 motion of the equinoxes, was the first who determined the quan- 

 tity of the solar year with any accuracy ; he was followed by 

 Ptolemv, and Rabbi Adda the i^w, who corrected the Hebrew 

 calendar about A.D. 340, and others ; and this quantity disco- 

 vered by Hipparchus is the nearest and most convenient of any 

 other for the joint motions of the sun and moon. I shall here 

 put down the several quantities deduced from his principle : 



1. Hip- 



