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ASTRONOMICAL PAPERS. loi 



ferving the eclipfes of Jupiter's fatclikes, the immerfion 

 or emerfion {hall often feem inftaataneous, or nearly fo, 

 equally to two obfervers in diftant places, and yet the ab- 

 folute times of the obfervations may differ a minute of time 

 or more from each other, owing to the difference of tele- 

 fcopes, weather, or other circumftances. Indeed, in the 

 prefent cafe, the limit of differences is certainly much nar- 

 rower; but what it is I ihall not at prefent venture to iuj;- 

 gefl, as that may better be done, when all the obfer- 

 vations that fliall have been made of the tranfit are col- 

 leded together. The telefcope which I ufed, was an ex- 

 cellent refleding one of two feet focus, made by the late 

 Ingenious Mr. Short, and is the fame with whichthe laft 

 tranfit was obferved here by Mr. Charles Green. I applied 

 the magnifying power of 140 times, and ufed imoaked 

 glaffes to defend the fight, which are much preferable to 

 black or red glaffes, as fhewing the objeds more diftind, 

 and being much more pleafant to the eye. 



I fhall now endeavour to defcribe, as accurately as I can, 

 fome other phoenomena which I noted during the immer- 

 fion of Venus, and to mention feme others, which by 

 fome ingenious perfons were expeded to have been feen, 

 but which I could not difcovcr. 



It had been thought by fome, that Venus's circumfer- 



cnce might probably be feen, in part at leafl, before fhe 



entered at 



upon the Sun, by means of the il- 



lumination of her atmofphere by the Sun; I therefore 

 looked out diligently for fuch an appearance, but could 

 fee no fuch thing. 



I was alfo attentive to fee if any penumbra or dufky 

 fliade preceded Venus's firfl impreffion on the Sun at the 

 external contaft, fuch a phoenomenon having been obferv- 

 ed by the Rev. Mr. Hirft, F. R. S. at the former tranfit of 

 Venus, in 1761, which he obferved with much care and 

 diligence at Madrafs, in the Eaff-Indies; but I could not 

 difcern the leaft appearance of that kind. I would not, 

 however, be therefore thought to call in queflion either 



Vol. I. 



O 



Mr. 



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