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ASTRONOMICAL PAPERS. 



7:^ 



5. Subtract D from a, multiply the rcmaindtT by D, and call \l\t fcjuare root oi the pro- 



Vtiid F,.=:.oo7<43o89. 



6. As three times thf Moon's mean dUUnce .from the I-^arth, in. f^'midiamttcrs of the Earth- 



is to }i, io isR, to the tanir. of the Sun's horary parallax, at his mean diftancc,=:r=8", 65. 

 7. As F. : 3 : : tho Mooxi's (iigan dhlance in miks: the Suu's mean dillaiicc in r 



mileS' 



94,9'3a,6oo, 



In determining the parallax of the Sun, from the ob- 

 fervation made in our obfcrvatory on the 3d of June, 

 I have only made ufe of the time of the internal contact, 

 as 1 noted it on that day, together with fome of my own 

 micrometer obfervatioas, without attending to thofe of the 

 other gentlemen who obferved with me. But as the So- 

 ciety has a right to exped a full account of the refult of 

 the other obfervations, which were made on that occafion; 

 and as fuch account may tend to corroborate the foregoing 

 calculations, I have, with Dr. Williamfon'y permiffion, 

 fubjoined a calculation of his, founded entirely on his owui 

 obfervation, which being veryfhort, I haye inferted entire 

 in his own words, except what refers to the manner in 

 which he judged of the contads, &c. which I have tran- 

 fcribed in another place, (fee page 46) From this, which 

 is very fimilar to the obfervations made by the other gen- 

 tlemen on that committee, the Society will perceive, that 

 our obfervations muft have been made with qonfiderable 

 accuracy, as the refult of the calculation is nearly the fame. 



\ 



Dr. WILLIAMSON'S Determination of the Parallax 



of the SUN, from his Obfervation of the Transit of 



VENUS, at P hiladelphiay June i^d^ 1769. 



i( 



w 



ITH a refrading telelcope, 24 feet long, which 

 magnified near 100 times, I obferved, 



■*> 



The external contaS at 2\ Ji\ 31 



// 



Internal do. at 



2. 



29-- 



ID 



Mean Time. 



'^ With a micrometer of Dollond's conftrudion, fitted 

 to a Gregorian refledor, v/hich magnified 100 times, I 

 meafured the diftance of Venus from the limb of the Sun ; 

 alfo the diameters of the Sun and VenuSj as follows : 



Mean 



