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76 



MATHEMATICAL and 



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ecliptical conjundion when the Sun's place was 2*. 13*, 

 ij^'. 20'', 5, as calculated by the aftronomer royal, on the 

 fuppofitiou that our obfervatory Is weft of Greenwich 5". 



o' . 35^'*^^' — ^^ ^^^ Sun's place in the eclipt, add his dift« 

 from the node of Venus i^ 8'. 25^', The fum is 2'. 14". 

 35*'.45'^5, the place of Venus'safcending node. 



" From the micrometer meafures above given, it ap- 

 pears that the center of Venus was at her neareft approach 

 to the center of the Sun at ^^, 21'. 44" mean time, or 5 

 43'', 59'' appar, time. But on account of the parallax of 



Venus, the appar. time at the center of the Earth was 4' . 

 48'' later, which brings it t0 5\ 28'. 47^^ as I have menti- 

 oned. From this dedud: the femidurat. 2\ ^^^ . 20, and 

 the remainder 2". 2,s' • 27" is the time of the internal con- 

 tad at the center of the earth. This contad 1 obferved as 

 above, at 2\ 29^ 10'' mean time, or 2\ 31'. 25'' ap- 

 parent time. This difference, therefore, viz. 4'. 2'^ is 

 the obferved effeds of Venus's parallax both in latitude 

 and longitude. 



" But on the fuppofition that the Sun's horizontal pa- 

 rallax, at her mean dift. from the earth was 8", 65, as 

 Mr. Short has ftated it at the former tranfit, then his ho- 

 rizontal parallax, on the 3d of June, the day of the tran- 

 fit, would have been 8'^5204, in which cafe the total effed 

 of her parallax, to haften the internal contad at Philadel- 



phia, fhould be 4'. i". Therefore, 



" As 4'. 1' is to 4'. ''2, fo is 8^5204 to 8^^y^^6, the 



Sun's horizontal parallax on the day of the tranfit, accord- 

 ing to the foregoing obfervations. 



*' Hence we have 8^^,685, the Sun's horizontal parallax 

 at his mean diftance from the earth. Then fay, 



*' As the Tang, of the Sun's horizontal parallax : is to 

 the femidiameter of the earth, 



" So is Rad. to the diftance of the earth from the Sun, 

 viz. 94791100 Englifli miles, taking the earth's mean 



femidiameter at 3985.4 miles. 



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