/ 



MAT H E M A T I C A L a xM d 



time^- From a mean of a number of good obfervationy, 

 the apparent diameter of the Sun was 31', ^o\6(d^ and 

 that of Venus 58^66; though I could not make it rayfelf 

 more than $%\ which was the fame we found it about a 

 fortnight before the tranfit. The proportion of their dia- 

 meters was nearly as i to 33. The nearefl approach of 

 their centers, at the middle of the tranfit, was taken with 

 the micrometer, and found to be 10' . 5^^ 



" The proportion of the diftances of the Sun and 

 Venus from the earth, at that time, was as 3,5143 ^^^ ^ 5 

 then (allowing the Sun's parallax at his mean dillanceto 



fj 



1761) the 



parallax of Venus was 3o",o4; the difference of their 

 parallaxes 21 '',49 is the parallax of Venus from the Sun. 

 The angle between the vifible way of Venus and the eclip- 

 tic, 8^ 34'. 17"; and the angle made by the axis of the 



ecliptic and equator, 7°. 3 



1 > 



their fum,, 15^ 37'. 24'', 



was the angle between the axis of the vifible way of Venus, 

 and the Earth's axis. The tranfit line, from total ingrefe 

 to the middle of the tranfit (meafured in time by the yj- 

 fible motion of Venus) was 2^- SS^ - 36"; but Venus was 



more accelerated in her .orbit (by parallax in longitude) at 

 the middle of the tranfit, tjian at total ingrefs; this dif- 

 ference of acceleration was x\ 'ii^' \ therefore from the to- 

 tal ingrefs to the middle of the tranfit was 2^^' 54'. 3^'. 

 Thence I conclude, that the 



o 



f Firft contad was at - - - 2^- 28'/ 

 But fcen by us, as above, at 2. 29. 43 > ap. time. 



Interior contad, 

 Middle of the tr 



2. 46. 35 

 - 5- 40- 3^ 



" Venus's 



* At the moment of ir.tcrior contact, the Sun's altitude was taken with the Jcxtanr, by 

 Mr. Mofes Brown, and by the HJIe by Captain John Burrough ; and both gave the time with 

 the cloclis within tw9 feconds. ' The tot^l ingrefs wns not fo infi-antaneous as I did expet^ it 

 would be, but the bright cufpB of the Sun, as they cncompaSTed Vt-nus, were much more ob- 

 tufe and there fcemcd to be a faint: junction of their limbs for at leaft 4 feconds; the moment 

 this' penimibral ligament broke, I proclaimed ihc time ; at firiU fufpcclcd tJie telefcope wa^ 

 not adjuded to a proper focus; but afterwards, by loolung at the folar fpots, &;c. I was con- 

 vinced of the contrary. During J:hc time we faw Venus upon the Sun, flie appeared to b- 

 furronndcd by a ring of a yellowiih colour; its width was about one tenth of the diameter 

 Venug. We fav/ nothing that might be talcen for a fatellite. 



\ When I calculated this tranfit, 1 fuppofed the longitude of our place to be much Icfs tJian* 

 : have fmce found it by obftrvation. By correding that error, the error in caieuUition will 



£ 



we 



itppcarlo be intoufulcrable 



