ASTRONOMICAL PAPERS; 



97 



*•' Veaus's parallax In longitude, at tlie middle of the 

 tranfitj was i8^',7; this was pafled over by Venus's vifihle 



fit, as 



monon in 4' . 44"; fo that the middle of the tran 

 feen from the center of the earth, was at 5^* 43', 6^' 



The true conjundion was 2^^ 21/' before the 



mean 



tune. 



middle of the tranfit, as feen from the earth's center; con- 

 fet|uCntly the true conjundion was at 5^* ig^ 45", mean 

 time. At which time, the place of the Sun and planet 



was Gemini io^^\ 27 





and the geocentric latitude of 



Venus 10' I9^\8 north. But her heliocentric latitude was 

 4' . O^'^j I ; and by the rules of fpherical trigonometry, the' 

 afcending node of Venus was i'^. 9^ 23^,5, in confequence 

 of the Sun, or in Ge^nini 14*^. 1^6' . 26'^^; 



" From the foregoing calculation it appears, that the 



mean motion of Venus is 



?>! 



1.1 



forward of what it ftands 



// 



in Dr. Halley's tables, and her afcending node 2'- 41 



" It is probable Dr. Halley's folar numbers need fome 

 corredion llkewife; the following may not be far from 

 truth, viz. add to Dr. Halley's mean motion of the Sun, 



for any year of the chriftian ?era, 25 , and to the apogee 



'6'. 18'' I for each century after 1700 add i4",666 to the 

 mean motion, and to the apogee 3'. ^^t^^ ; then by ma 



king ufe of the Parifiaa^ equation of the Sun's center, his 

 place may be had within a fmall matter of truth* 



" By taking the mean of a number of obfervations^ the 

 latitude of our obfcrvatory was found to be 41**. 50'. 41'' 

 northf. The longitude was obtained by obferving the 

 emerfions of Jupiter's fatellites, compared with the corref-- 

 ponding obfcrvations mad6 at Cambridge, in New-Eng- 

 land, by Mr, Winthrop, which he v^as fo kind as to fa-- 



vour 



wl 



* Acconling to tlic Piinfum hypothefis, the cccenirity of the earth's orb Is t6So parts, of 

 wnich the mcun diO.ancc of the earth from the Sun is roo,ooo. 



. f The hititiulc of the pkce being of groat confequcnce, and the fextant and llile not giving 

 it fxadly alike, the pcrfcvtring Mr. Brown contrived to make ufo of the micrometer asalens^ 

 which he placed on his houfe, twenty fcven feet liigh, and exactly perpendicular to a center 



th 



The -- - -, ,, . . 



found did not difler from each other more than 15 feconds. At the tune this was done, w^ 



had ften no account that a glafs had been made ufe of, as here dcfcribcd ; but iincc this went 

 to the prcfs, we learn from Dr. Long's aflronomy, that he found the latitude of Cambridge, in 

 Englandj by the fame method. 



'^^^ 



