32 PHILOSOPHICAL TRANSACTIONS. [aNNO 1763. 



durations observed at the different places in the north (the method of which is 

 afterwards given) the parallax of the sun will come out as follows, when they are 

 compared with that measured at Rodrigues : 



Cajan. Calm. Tobol. Torn. Upsal. Stock. Abo. Herno. 

 Rodrigues 8".60 8".58 8".6"5 8" 48 8".6o 8".40 8".63 8".55 



The mean of these 8 comparisons gives the sun's parallax = 8'. 56, being 

 the very same as that which we found before by the comparisons of the inter 

 nal contacts. 



Again let us reduce the observed durations, at the following several places, 

 to the centre, on the supposition that the sun's parallax is = 8 '.56, as in the 

 following table. 



1. 



Tobolsk. 

 48"" 53'=Obs. Du. 

 9 6 = Parallax. 



5 58 59 = Cent. D. 



5. 



Stockholm. 



5 50 42 = Obs. Du. 



7 37 = Parallax. 



58 19 = Cent. D. 



9- 

 Calcutta. 

 50 36 = Obs. Du. 

 7 35 = Parallax. 



2. 



Cajaiieburg. 



5" 41)"' 54'=Obs.Du. 



8 8 = Parallax 



5 58 



50 

 7 



2 = Cent. D. 



6. 

 Abo. 



9=Obs.Du 

 49 = Parallax. 



57 58 = Cent. D. 

 10. 

 Madras. 

 51 43 = ObsDu. 

 6 35 = Parallax. 



3. 

 Tornea. 

 50°' 9'=Obs.Du. 

 8 3 = Parallax, 



5 58 12 = Cent. D. 



7. 



Hernosand. 



5 50 26 = Obs, Du. 



7 39 = Parallax. 



5 58 5 = Cent. D. 



II. 



Grant Mount. 



5 51 20 = Obs. Du. 



6 35 = Parallax. 



5» 50' 

 7 



4. 

 Upsal. 



' '26'= Ob.s. Du. 

 HG = Parallax. 



5 58 2 = Cent D. 



8. 



Calmar. 



5 5> 39 = Obs.Du. 



7 24 = Parallax. 



5 58 3 = Cent. D. 



12. 



Abo. 



5 51 33 = Obs.Du. 



6 26 = Parallax. 



5 58 11 = Cent. D. 5 58 18 = Cent. D. 5 57 55 = Cent. D. 5 i7 55 = Cent D. 



The mean of these 12 central durations gives the mean central duration = 5^ 

 58"" 5*. From this central duration we shall find that the geocentric least distance 

 of the centres is = 571" or 9' 31". Let us compare the above apparent least 

 distance of the centres measured at Rodrigues, with this geocentric least distance 

 of the centres, and we shall find that the parallax of the sun thence resulting is 

 = 8".56j the same as before. These results of the parallax, arising from the 

 comparisons of the apparent least distances of the centres, agreeing with the 

 former determinations of the parallax by the internal contacts, are a proof of the 

 accuracy of this measurement of the greatest distance of the limbs made by M. 

 Pingr6 at Rodrigues. 



There are ) 2 places at which the total duration was observed, 3 of these had 

 a northern parallax of latitude at the middle of the transit, the other g had a 

 southern parallax of latitude. Let the apparent least distance of the centres at 

 each place of observation be found by the following method ; let these be com- 

 pared together, and we shall have the parallax of the sun resulting from them. 

 For this purpose Mr. S. computed the apparent least distance of the centres at 

 the 8 following places, and compared them with the apparent least distance of the 



