16 Remarki on the Lunar Theory. 



tcceleration in an entire period is 66" 27' 12''"7 ; in a terrestrial 

 period 32' 43"-3. This period of eclipses, although longer than 

 Mr. Yeates appears to see through, is notwithstanding the least 

 which comprises all the phaeuomena of any respective eclipse ; 

 and which I presume is not likely to be superseded by that which 

 he is endeavouring to establish. 



According to Mr. Ferguson, the entire period of an eclipse is 

 13380 years, and not 12492 as erroneously stated by Mr. Yeates; 

 this being the time only in which the eclipse is passing through 

 the expunsium. — Vide Ferguson's Astronomy referred to by 

 Mr. Yeates ! 



At page 443 we are informed that in 912 solar vears there 

 .•ire 228 bissextiles, and t:even intercalary days, in all 23.5 days. 

 A little further Mr, Y. observes that in 912 solar years there are 

 940 lunations. — 1 cannot, I confess, perceive the existence of this 

 harmony, although we are told it really subsists ! and is con- 

 firmed by every evidence of observation ! ! In the first place 

 there are but about 221 days over and above the common years 

 of 365 davs each, instead of 235. According to the Julian rec- 

 koning there are 228 bissextiles, but by the Gregorian account, 

 seven are not bissextiles, being centenary years ; of course there 

 are but 221 in all (each of which is bissextile) instead of 235 as 

 erroneously stated. With respect to 912 solar years, containing 

 040 lunations: — this I shall leave for /iwe and the curious to 

 construe. Mr. Yeates in reference to long lunar periods, p. 345, 

 remarks — yill this arises from our imperfect knowledge cf the 

 lunar theory. I beg leave to observe that modern astronomers 

 are not quite so ignorant as Mr. Y. endeavours to make ufj- be- 

 lieve ; and as proof of this assertion I refer liim to the articles 

 Astronomy, Acceleration, Moon, &;c. in most of our modern E«- 

 cyclopedias, the Astronomical Works of Professor Vince, Gre- 

 gory, Squire, and Woodhouse ; also Lalande's Astronomy, La- 

 place's Celestical Mechanics, and System of the World ; Delam- 

 bre's Theoretical and Practical Astronomy ; Biot's Treatise on 

 Elementary and Physical Astronomy ; and the Solar and Lunar 

 Tables of Delambre, Burg, and Burckhardt. In perusing the. 

 above works the reader will there perceive the advances which 

 have been made towards perfecting the lunar theory, and the 

 theory of the celestial motions in general ; originating with the 

 fortunate idea of applying analvsis to the celestial motions, and 

 by reducing them to differential ecjuations, which have been ri- 

 gorously integrated, or by converging approximations. Thus the 

 theory of gravitation has given an unexpected precision to astro- 

 nomical tables. 



The lunar tables in the time of Sir Isaac Newton gave the }) *« 

 longitude only to within about five minutes of a degree from the 



truth ; 



