CREATES* EQUATION OF A PLACET. £"7 



that of Ceres, where the eccentricity is -08140, and error 4| #/ . 

 (Pa. 60. No. V.) In the cafe of the Georgian the error or 

 difference , as ftated in the table, is much too great to corre- 

 fpond with the eccentricity. But here I conceive there is a 

 miftake in the determination of the eccentricity : for, accord- 

 ing to a mean from various aftronomers [Mechain, Hennert, 

 JDe la Place, Zach, and Robifon,) the proportional mean dif- 

 tance of the Georgian is not 1918352, but 1908352. Hence 

 then, we have Tir §-|||$ = -04.75824 = nat. fine of 2° 43' 

 38 -4", differing -5% of a fecond from the determination of La- 

 lande. And, in the cafe of Jupiter, where the eccentricity is 

 •04807, the correfponding difference is -j^ of a fecond; 

 which is a little larger than the former, as it ought to be. So 

 that it appears, as well from Mr. P's table as from the invefti* 

 gation, that this method does not furnifli a refult fufficiently 

 accurate except when the eccentricity is pretty fmall. 



Before I conclude, I would juft beg to remark, that this The converfe 

 method, though new to Mr. Pearfon, is in reality well known. an alogy^° Mr* 

 An analogy which is, in fact, the converfe of this, though ex- known, 

 prelled rather lefs eommodiouily, is given with a demonftra- 

 tion, in La Caille's Aftronomy, art. 147. Vince's Aftron. 

 art. 231. and my Aftron. art. 344. And I believe it is alfo 

 given in the excellent work of La Lande ; but as I have not 

 that performance at hand, I cannot now refer to the place. 

 Another analogy precifely to the fame effect, and deduced 

 from the fame principles, may be feen in art. 249. Book V. 

 Robertfon's Navigation, and under the article Eccentri- 

 city in Dr. Hutton's Math, and Phil. Dictionary. It muff 

 afford great fatisfaction to a gentleman of Mr. Pearfon's can- 

 dour and liberality, to find that the analogy which he acci- 

 dentally ftruck out, is the converfe of oue which admits of a 

 fimilar demon (Iration, and has been long ufed by aftronomers 

 as an eafy and excellent approximation. 

 I am, Sir, 



Your\s with much refpecr, 



OLINTHUS GREGORY. 



F 2 II. On 



