s 



lOO 



MATHEMATICAL and 



of 



over the SUN, and the Eclipse of 



J' 



1769, 7nade at //?^ Royal observatory, 



M 





B. D. F, R. S. and Aftronomer Royal. 



Communiaated to the Society by Dr. Smith, and ordered to 



puhlijided at a meetings May i8th^ ^77^' 



I ^ 



■1 



HE weather, wliich had hecn cloudy or rainy here, 



with a fouth wind, for the greateft part of the day, 



began to clear up at four o'clock in the afternoon, the 

 wind having returned to the weft, the fame quarter in 

 which it had been the afternoon before, which was re- 

 markably fine and fercne, though it changed early in the 

 morning preceding the tranfit. Towards the approach of 

 Venus's ingrefs on the Sun, the fky was become a,:>ain 

 very fercne, and fo continued all the evening, which af- 

 forded as favourable an obfervation of the tranfit here as 

 could well be expeded, confidering that the Sua was 

 only 7'^. 3' high at the external, and 4''- ^^^ at the inter- 

 nal contad:, I obferved the external contact of Venus at 



7^. 10'. 58' apparent time, with an uncertainty fcemingly 

 not exceeding 5''; and the internal contact, by which I 

 mean the completion of the thread of light between the 

 circumferences of the Sun and Venus, at 7^- 29^ 23" ap-- 



. ' , ~ \ .'; for 



fo long was the thread of light in forming, or the Sun's 



parent time, with a feeming uncertainty of only 3 



light in flovv^ing round and filling up that part of his cir- 

 cumference, which was obfcured by Venus's exterior limb. 

 Neverthelefs, I would not hence infer, that obfervations 

 made by aftronomers In diftant places fliould agree together 

 within fuch narrow limits; for I know they will not even 

 in the fame place, and that a difference in the flcill or 

 judgment of the obfervers, in the telefcopes, and perhaps 

 in fome other little circumftances, not eafily diftinguifhed, 

 may produce much greater difagreements, efpecially if tlie 

 Sun be low, as it was here; in like manner as in ob- 



ferving 



\ 



i^ 



