M, DE Z.Aeifs AfronomkfJ, Ohfervrfilom, - 15^. 



S' I R, ' Lyons-, May 4, 1783. 



LATELY I received' f-rom-.the" Obfervfltory nt MarfejUes the 

 ©blervatlon of the trnnfit of Mercury, which happened the 12th 

 Nov. I ; 82. The llcy not beings very favourable, only the two in- 

 ternal contadl's w^ere obierve'd';. the firft internal contail was ob- 

 ferved' byM. St. Jav-ques df. Sylvabellf.,' at 3 h. 18 '30^"'' 

 apparent time j. the, lad internal conta6t by M. St. Jacques, at 

 4h.' 30^ \(^" \ by M. Bernard, his Adjunclus, at4h. 29^ 13^'. 

 The'nea'refl- diftances of Mercury's limb, to that of the fun- iiv 

 tHe f>Dr.tlieni parrdf its diik were at: 



'if. 





3-33^4 



3 42 57 I 34 J> parts of the micrometer, 



4 22 iy\ 19 



The apparent dJa meter of the flrn was 2174 parts of this m:^ 

 crometer : L fuppofe the- before-mentioned 2174 parts— 32^ 

 '26^^,9-. T conclude farther- by the ebfervatibhs, the middle of 

 the'tranfit at 3h. 54' y\2^^; whe-peas I fix, by interpolation, 

 i:he diftances of the limbs at 3 h. 54^ 7''>25 = 35^^,6 i I have 

 therefore feml-diameXer of the fun — 16' 13^^,4-35-^,6 = 

 1 5^ 3-7'^8 -K^emi-diameter of Mercury — 6'^ = 15^ 43'^8 — totlie 

 leaft diftanoe of centers of the iun aiid Mercury. By M. de 

 LA Lande's tables it is 15^ 42'', only a difference of L^S. 



M. Waulqt at. Earis has obferved this tranHt at the Royal' 

 Obfervatory,, 



Firft external cmitaiSi* 2 56 28 



Firft internal contact 3. 2. 3. 



Second - - 4 i 7 i 8 



Second external - 4 22 53 

 5. Vcml^- 



