J? 



\ 



I iO 



M ATHEM 



AND 



" Thefe obfervations were made with the 2 feet refle*^:* 



or, and the magnifying power 120 



D. h. m. fee. 



J 



9 



20. 



J 



Jup 



not been from under the clouds lo^'^ 

 when he faw the fatelUte, yet he 



reckons the obfervation good. 



J 



II, 13. 46 Em. ift fat. 



J 



piter 

 good. 



but the obfervation pretty 

 Thefe emerfions were ob- 



ferved with the fame telefcope, but 

 with the magnifying power 100. 



Comparing the obfervation of the contaCts of Venus at 

 the Lizard with his own at Greenwich, making a fmall 

 allowance for the difference arlfing from the effed of par- 

 allax at the two places, Mr. Mafkelyne makes the differ- 

 ence of meridians of Greenwich and the Lizard. 

 By the external contad of Venus 20^ S3^^ 

 By the internal contad of ditto 21 01 



^ 



'k 



of time. 



20 57 



The mean by the contads 



By the two emerfions, making a fmall allowance for the 



difference of brightnefs of the telefcopes, he makes the 



difference of meridians as follows, viz. 

 By the firft emerfion 

 By the fccond emerfion 



The mean of thefe is - 



21 . 07 

 21. 52 



21. 13,25 



21. 29,5 

 The mean by the contads - 20. 57 



Mean of the two means 



But Mr. Mafkelyne, till he has time to compare the o- 

 ther obfervations, fixes on 21'. o'' of time— 5°. 15'. of the 

 equator, for the difference of longitude of the Lizard wcfl 



of Greenwich, 



The above is taken from the nautical almanac for 

 1771; and it was thought might be a proper addition to 

 the foregoing account of the tranfit of Venus, at Greenwich, 

 drawn up by the Aftronomer Royal. A LETTER 



