S¥i 



r;.^ 



\ 



148 



MATHEMATICAL and 



Nothing but thefmallnefs of the prefent Comet can pre- 

 vent Its being fecn at this time (if indeed it be not feen); 

 for it muft rife in the morning before day, and continue 

 todo fo for fome months; but will at length retire to a prodi 



gious diftance beyond the reach of the befl glafles, in the 

 26th degree of Virgo, and very little north of the ecliptic. 



The earth's place June 27th, 14^. at the meridian of 

 Greenwich, is computed to be 9'- 6^. 16'. 7'' and the ex- 

 centricity of its orb 168 fuch parts, as its mean diflance 

 is loooo. If any one would compute the vifible place of 

 the Comet, from the principles above laid down, he muft 

 find the Sun's place, or rather the earth's, by the tables 

 he makes ufe of, to June 27, I4\ at Greenwich, and as 

 much as he finds itfafter or flower than 9'- 6^ 16'. 7'' fo 

 much muft he add to, or fubtra£t from, the place of the 

 perihelion, not neglc£ting feconds, otherwife a very great 

 difference might arife in the calculation. 



If the reduction to the plane of the ecliptic be applied, 

 50" may be fubtrafted from the place of the perihelion. 



NoRRiTOK, 7///J/24, 1770. D. RITTENHOUSE. 





LETTER 



II. 



BEAR SIR, 



w 



Magazine, for J 



M. Meffi 



by which it appears, 



twelve days fooncr than wc did here; bccaufe it affords 

 another opportunity of comparing this Comet's motion 



with my theory. 



According to M. Meffier's obfervation, on the nitrht be- 



tween the I 



J 



cenfion was 270". 57'. 37'' with 15^^. S5^ ' ^^" South de- 

 clination. The hour of the night is not mentioned, but 

 the place of the Comet was no doubt determined by its 

 paffing the meridian, which he fays was about midnight, 

 that is at Philadelphia, June 15th, y^. Time 



