t^ 



y" 



162 



MAT 



E M A T I G A I 



^ AND 



aftronomical reckoning, Odober 27^ 19^*37'. ^^" ; and 

 the leaft diftance of the centers, acccording to Dr. Ilalkjy 



Taking this as our ground work^^ let us com'- 



20 



3- 



pare theory with obferva^ion. 



^J^lI. h e o r y . 



October. Middle reduc- Lealt diil. 



ed to Green- of centers. 

 wich. 



Years. 

 ift Tranfit 1631. 



2d Trunfit 1677. 



+46 



o, 



h. m.iec. M. fee. 



T9- 37- 5S 3. ao 

 4. 51 r^i. aaN. 



By O B S K R V A '1' I O JN .s. 



^1 '■ ■ ^^™*l-M I I III 1^ |l 



j-JiUercii';. 



Middle reduc" Difference 

 ed to Green- later in 46 



hHVJ 



^8, 



o. 28,55 4- 4^ 

 4. 51 +1. aaN. 



3d Tranfit I7^3-UB, 5- 19- 55' 6. 4 



-(-46 o, 4. 51 ^-i. 2^ N 



ith Tranfit 1769. 'aB, to 10.55' 7* ^^ 



with. 



D. h, ni. fee, 

 a7. 19- 37- 55, 



years, 

 H. m. fee. 



A' 50. 5 



z8, 0, sS. 



^B, 5 





™~™,.™-™™,-»-j7 4- 47- 

 28. 10. I. 5^:5 



22 



l>caii 

 dlft. of 

 Cen- 

 ters. 

 ni, fee. 

 3. 20 



more N. 

 in 46 

 years, 

 in. fcc- 

 I, iS 



7. 3* 



ThuB it ai^pcars, that, the ohfervations do not quite agree with the theory ; the latitude being 

 incrcafed by the laft tranfit about -J of a minute more north, than the theory would jrive, and 

 the time of the middle falling about 4^ too foon. Whether tliis ean be aeeounted for from a re- 

 examination of the ohfervations themfdlvca, or by any corrtdion in the niouon of ^ 's nodea, 

 may be wortJiy of further en<|uiry. 



The Sun's Parallax deduced from a comparlfon of the 



NoRRiTON and Jo7ne other Kixxtnczxi ohfervations of the 



tranfit of Venus., 17O9 ; ivith the Greenwich and other 

 European ohfervations of the fame. By William 

 Smith, D. I), Provojl College Philadelphia. 



N E can fcarcely enter upon this fubjccl, without 



_^ admiring the lagacity of the great Dr. Halley^ wlio 

 firfl conceived the method of afcertaining the Sun's paral- 

 lax (that is, the angle which the earth's femidiametcr 

 fubtendsat the Sun^) and confequently the dimenfions of 

 the whole folar fyfl:em> either from the total duration of a 

 tranfit of Venus, duly obfervcd in one fnigle place of the 

 earth properly fituated^ or from the difference of abfolute 

 time that elapfcs between the obfervations of the conta6ls 

 of the Sun and Venus in different places. 



The latter of thcfe methods is what aRronomers in 

 general prefer; yetj even in that, a concurrence of fo many 



circumftances 



/ 



I' 



